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ISSN 1092-194X
FLORIDA MARINE RESEARCH INSTITUTE
TECHNICAL REPORTS
Mercury Levels
in Marine and Estuarine Fishes of Florida
1989–2001
Douglas H. Adams, Robert H. McMichael, Jr., and George E. Henderson
Florida Fish and Wildlife
Conservation Commission
FMRI Technical Report TR-9 Second Edition, Revised • 2003
Jeb Bush
Governor of Florida
Florida Fish and Wildlife Conservation Commission
Kenneth D. Haddad
Executive Director
The Florida Marine Research Institute (FMRI) is a division of the Florida Fish and Wildlife Con-
servation Commission (FWC). The FWC is “managing fish and wildlife resources for their
long-term well-being and the benefit of people.” The FMRI conducts applied research pertinent
to managing marine-fishery resources and marine species of special concern in Florida.
Programs at the FMRI focus on resource-management topics such as managing gamefish and
shellfish populations, restoring depleted fish stocks and the habitats that support them, protecting
coral reefs, preventing and mitigating oil-spill damage, protecting endangered and threatened
species, and managing coastal-resource information.
The FMRI publishes three series: Memoirs of the Hourglass Cruises, Florida Marine Research Publi-
cations, and FMRI Technical Reports. FMRI Technical Reports contain information relevant to
immediate resource-management needs.
Gil McRae, Chief of Research
James F. Quinn, Jr., Science Editor
Institute Editors
Theresa M. Bert, Paul R. Carlson, Mark M. Leiby,
Anne B. Meylan, Robert G. Muller
Judith G. Leiby, Copy Editor
Llyn C. French, Publications Production
Mercury Levels
in Marine and Estuarine Fishes
of Florida 1989–2001
Douglas H. Adams
Florida Fish and Wildlife Conservation Commission
Florida Marine Research Institute
1220 Prospect Avenue, Suite 285
Melbourne, Florida 32901
Robert H. McMichael, Jr.
George E. Henderson
Florida Fish and Wildlife Conservation Commission
Florida Marine Research Institute
100 Eighth Avenue Southeast
St. Petersburg, Florida 33701
Florida Fish and Wildlife Conservation Commission
FMRI Technical Report TR-9
Second Edition
Revised
2003
Cover Photograph
Collected fish aboard FWC research vessel on the Atlantic coast of Florida.
Photo by D. H. Adams
Copies of this document may be obtained from
Florida Marine Research Institute
100 Eighth Avenue SE
St. Petersburg, FL 33701-5020
Attn: Librarian
Document Citation
Adams, D. H., R. H. McMichael, Jr., and G. E. Henderson. 2003. Mercury levels in marine and
estuarine fishes of Florida 1989–2001. Florida Marine Research Institute Technical Report TR-9.
2nd ed. rev. 57 pp.
Document Production
This document was composed in Microsoft Word® and produced using QuarkXPress® on Apple
Macintosh® computers.The headline font is Adobe® Avant Garde,the text font is Adobe® Palatino,
and the cover headline is Adobe® Gill Sans.The cover and text papers are Consolidated Fortune
Recycled.
The cover and text papers used in this publication meet the minimum requirements of the
American National Standard for Permanence of Paper for Printed Library Materials Z39.48—1992.
Table of Contents
ACKNOWLEDGMENTS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ii
ABSTRACT . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1
INTRODUCTION . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1
METHODS AND MATERIALS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2
RESULTS AND DISCUSSION . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4
Bull Shark . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4
Blacktip Shark . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5
Atlantic Sharpnose Shark . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6
Bonnethead Shark . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6
Atlantic Stingray . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7
Ladyfish . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8
Hardhead Catfish . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9
Gafftopsail Catfish . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9
Common Snook . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .10
Red Grouper . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .12
Gag . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .12
Bluefish . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .13
Cobia . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .14
Crevalle Jack . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .15
Greater Amberjack . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .16
Florida Pompano . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .16
Permit . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .17
Dolphin . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .18
Gray Snapper . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .18
Tripletail . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .19
White Grunt . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .20
Pigfish . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .20
Sheepshead . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .21
Sand Seatrout . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .21
Spotted Seatrout . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .22
Spot . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .23
Southern Kingfish . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .24
Atlantic Croaker . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .25
Black Drum . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .25
Red Drum . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .26
Striped Mullet . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .28
Great Barracuda . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .28
Wahoo . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .29
King Mackerel . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .29
Spanish Mackerel . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .31
Gulf Flounder . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .31
Southern Flounder . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .32
SUMMARY . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .33
LITERATURE CITED . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .34
APPENDIX TABLE . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .50
i
Acknowledgments
We thank the staff of the FDEP Division of Technical Services for the laboratory analyses that made this
study possible. We greatly appreciate the efforts of the FMRI Fisheries-Independent Monitoring Program
and Fisheries-Dependent Monitoring Program personnel for their assistance in collecting fish and pro-
cessing samples, as well as the many recreational and commercial fishermen who allowed us access to
their fish. We also thank Cape Canaveral Scientific, Inc., for additional shark samples and the at-sea
observers and G. Burgess of the Commercial Shark Fishery Observer program for tissue samples from
three white sharks. Thanks to M. Byerly, J. Guenthner, S. Harkey, and G. Onorato for sample and data
management during various periods since 1989. T. Atkeson, L. French, J. Leiby, G. Onorato, R. Paperno,
and J. Quinn offered helpful suggestions for improving the manuscript. Fish illustrations are the work
of Diane Rome Peebles. This study was supported in part by funding from the Department of the Inte-
rior, U.S. Fish and Wildlife Service, Federal Aid in Sport Fish Restoration, Project F-43, and by State of
Florida Saltwater Fishing License monies.
Acronyms of agencies cited in this report
DEP Florida Department of Environmental Protection
DOH Florida Department of Health
EPA U.S. Environmental Protection Agency
FDA U.S. Food and Drug Administration
FMRI Florida Marine Research Institute
FWC Florida Fish and Wildlife Conservation Commission
HRS Florida Department of Health and Rehabilitative Services
NMFS National Marine Fisheries Service
SAFMC South Atlantic Fishery Management Council
Please contact the following agencies for further information
For information regarding mercury in marine fishes and other marine fisheries issues:
Florida Fish and Wildlife Conservation Commission
Florida Marine Research Institute, Education and Information Office
100 8th Avenue SE
St. Petersburg, FL 33701-5020
Te l 727-896-8626 Fax 727-893-9183 Web www.floridamarine.org
E-mail mercury@fwc.state.fl.us
For information regarding mercury management, regulation, and science issues:
Florida Department of Environmental Protection
Mercury Program Coordinator
Twin Towers Building 669-A, MS-6540
2600 Blair Stone Road
Tallahassee, FL 32399-2400
Te l 850-245-8305 Fax 850-245-8408
thomas.atkeson@dep.state.fl.us
For information regarding mercury-related public health issues:
Florida Department of Health
Bureau of Community Environmental Health
4052 Bald Cypress Way, Bin A08
Tallahassee, FL 32399-1712
Te l 850-245-4299 Fax 850-922-8473
Joe_Sekerke@doh.state.fl.us
Florida Department of Health
Office of Communication and Health Promotion
4052 Bald Cypress Way, Bin A04
Tallahassee, FL 32399-1705
Tel 850-245-4111 Fax 850-410-3049
Rob_Hayes@doh.state.fl.us
ii
Mercury Levels
in Marine and Estuarine Fishes
of Florida 1989–2001
Abstract
The Florida Fish and Wildlife Conservation Commission’s Florida Marine Research Institute (FWC-FMRI) has
examined total mercury levels in muscle tissue from a variety of economically and ecologically important species
as part of an ongoing study to better understand mercury contamination in marine fishes.The FWC-FMRI Mer-
cury Program is one of the most comprehensive programs in the United States for monitoring mercury levels in
marine and estuarine fishes. Because mercury, a toxic metallic element, has been shown to bioaccumulate in fish
tissue, humans consuming fish can potentially consume significant levels of mercury. We examined the concen-
tration of total mercury in 6,806 fish, representing 108 species from 40 families. Species represented all major trophic
groups, from primary consumers to apex predators.The majority of individuals we examined contained low con-
centrations of mercury, but concentrations in individual fish varied greatly within and among species. Species
with very low mean or median mercury concentrations tended to be planktivores, detritivores, species that feed
on invertebrates, or species that feed on invertebrates and small fish prey. Apex predators typically had the high-
est mercury concentrations. In most species, mercury concentration increased as fish size increased. Sampling
in Florida waters is continuing, and future research relating mercury levels to fish age, feeding ecology, and the
trophic structure of Florida’s marine and estuarine ecosystems will help us better understand concentrations of
this element in marine fishes.
Introduction
Florida’s marine and estuarine waters support pro-
ductive commercial and recreational fisheries. During
2000, approximately 53 million pounds of fish valued
at $74 million were landed by Florida’s commercial
fisheries (Murphy et al., 2001). In Florida’s recreation-
al fisheries during 2000, of the approximately 150
million fish caught, 69 million fish (64 million pounds)
were retained for consumption (Murphy et al., 2001).
Mercury, a toxic metallic element, has been shown
to bioaccumulate in fish tissue, which can be a major
source of mercury in human diets (Phillips and Buh-
ler, 1978; Turner et al., 1980; Lyle, 1986). Fish consumption
has been positively correlated with mercury level ele-
vations in humans (Choy et al., 2002; Hightower and
Moore, 2003). Concerns about mercury contamination
in Florida fishes arose in 1982 when a study by the
Florida Fish and Wildlife Conservation Commission
(FWC), Department of Health (DOH), and Depart-
ment of Environmental Protection (DEP) detected
elevated mercury levels in largemouth bass, Micropterus
salmoides, in northwest Florida. Additional studies fur-
ther identified elevated levels of mercury in freshwater
fish species in Florida (Ware et al., 1991; Lange et al.,
1993). In 1989, the DOH issued its first health advisories
warning of excessive mercury levels in freshwater fish
from approximately 800,000 hectares of Florida’s fresh-
water systems (Lange et al., 1993). In 1989, the FWC’s
Florida Marine Research Institute (FWC-FMRI; for-
merly of the DEP), working cooperatively with other
state agencies, began an ongoing study to investigate
mercury levels in marine and estuarine fishes of Flori-
da. Collection of marine and estuarine fish samples by
FWC-FMRI began in April of 1989. In May 1991, results
from this study and other research prompted the DOH
to issue a health advisory urging limited consump-
tion of all shark species from Florida waters (HRS,
1991). Because mercury concentrations were in excess
of State of Florida guidelines, DOH recommended
that adults should eat shark no more than once a week
and that children and women of childbearing age
should eat shark no more than once a month. In Octo-
ber 1995, a second health advisory was issued
recommending limited consumption of several marine
species from certain portions of Florida’s coastal waters:
gafftopsail catfish, Bagre marinus; crevalle jack, Caranx
hippos; spotted seatrout, Cynoscion nebulosus; ladyfish,
Elops saurus; and Spanish mackerel, Scomberomorus
maculatus (HRS, 1995). In June 1996, a third health advi-
sory urging limited consumption was issued because
of high levels of mercury in king mackerel, Scombero-
FMRI Technical Report TR-9 1
Mercury Levels in Marine and Estuarine Fishes of Florida 1989–2001 Adams et al.
Figure 1. Map of study areas in Florida where fish used in mer-
cury analyses were collected.
morus cavalla, caught in the Gulf of Mexico (HRS, 1996).
On 23 March 2000, the states of Florida, Georgia, North
Carolina, and South Carolina issued a joint health
advisory regarding high levels of mercury in large
king mackerel from the southeastern United States
coastline (DOH, 2000).The consumption limits reflect-
ed those outlined in Florida’s 1996 advisory.The other
Gulf of Mexico states took independent action and
the expanded scope includes all Atlantic and Gulf of
Mexico waters in the southeastern United States. In Jan-
uary 2003, an updated advisory was issued that
recommended no consumption of large sharks (>43
inches, or approximately 1,090 mm total length), and
limited consumption of sharks less than 43 inches
(approximately 1,090 mm total length). Limited con-
sumption of the following fish in all coastal areas of
Florida was also recommended: large (>20 inches or
approximately 508 mm total length) spotted seatrout,
Cynoscion nebulosus; little tunny, Euthynnus alletteratus;
cobia, Rachycentron canadum; greater amberjack, Seri-
ola dumerili; bluefish, Pomatomus saltatrix; and crevalle
jack, Caranx hippos. The January 2003 advisory also
recommended limited consumption of the following
fishes from certain portions of Florida’s coastal waters:
gag, Mycteroperca microlepis; Spanish mackerel,
Scomberomorus maculatus; gafftopsail catfish, Bagre mar-
inus; common snook, Centropomus undecimalis; red
drum Sciaenops ocellatus; great barracuda Sphyraena
barracuda; spotted seatrout, C. nebulosus (all sizes); per-
mit, Trachinotus falcatus; wahoo, Acanthocybium solanderi;
ladyfish, Elops saurus; snowy grouper, Epinephelus nivea-
tus; blackfin tuna Thunnus atlanticus; and almaco jack
Seriola rivoliana (DOH, 2003).
Current DOH guidelines recommend that fish
containing less than 0.5-ppm of total mercury be con-
sumed following federal EPA guidelines and that fish
containing 0.5 to 1.5 parts per million (ppm) of total
mercury should be consumed in limited amounts; fish
containing greater than 1.5 ppm of total mercury should
not be consumed (see Florida Department of Health
Guidelines, facing page). DOH guidelines are direct-
ed primarily at recreationally caught fish.The Florida
Department of Agriculture and Consumer Services in
conjunction with the U.S. Food and Drug Administra-
tion regulates the commercial seafood marketplace.
In this report, we offer a summary of the total mer-
cury levels found in marine and estuarine fishes
collected in Florida waters from April 1989 to May
2001. This is a continuation of a technical report pro-
duced by FWC-FMRI in 2001 (Adams and McMichael,
2001) and includes data regarding many additional
species and 3,979 additional fish samples collected
between January 1995 and May 2001.
Methods and Materials
Fish samples analyzed in this study were collected by
staff from FWC-FMRI’s Fisheries-Independent Mon-
itoring Program from Florida estuaries and adjacent
coastal waters or from recreational and commercial
fisheries in the nearshore and offshore waters of Flori-
da. Beginning in July 2000, samples were also collected
from recreationally and commercially landed fish by
staff from FWC-FMRI’s Fisheries-Dependent Moni-
toring Program. Study areas included the Indian River
Lagoon,Tampa Bay, Charlotte Harbor, Choctawhatch-
ee Bay, Cedar Key, Apalachicola Bay, Volusia County,
Tequesta/southern Indian River Lagoon, Sarasota Bay,
Everglades coastal waters, Florida Keys/Florida Bay, and
the northeast Florida area as well as nearshore and off-
shore waters of the Atlantic and gulf coasts adjacent
to these areas (Figure 1). Samples were collected from
April 1989 to May 2001.
Fish were placed directly on ice and returned to the
laboratory or were processed in the field; species, stan-
dard length (SL), and sex were recorded. Precaudal
length (PCL) was recorded for all shark species, and disk
width (DW) was recorded for all ray species. To allow our
data to be compared with those from other studies,
total length (TL), fork length (FL), and other morpho-
metric characters were also measured. When possible,
maturity of sharks was determined by macroscopic
examination of gonads, examination of claspers on male
specimens, or by comparison of shark size with estimates
of size at birth or maturity from previous studies.
A clean stainless-steel knife was used to remove
axial muscle tissue samples from the left dorsal area
2 FMRI Technical Report TR-9
Adams et al. Mercury Levels in Marine and Estuarine Fishes of Florida 1989–2001
Florida Department of Health Guidelines
for Issuing Fish Consumption Advisories
Mercury level above 1.5 ppm—No Consumption.
The specific fish species from the specific water body should not be eaten in any amount.
Mercury level 0.5 to 1.5 ppm—Limited Consumption.
Women of childbearing age and children under age 10 should not eat more than 8 ounces of listed fish species
from specified water bodies over a 4-week period. Others should limit consumption of listed fish species
from these locations to no more than 8 ounces a week. (Note: A 4-ounce serving of raw fish is about the size
of a slice of sandwich bread.)
Mercury level below 0.5 ppm—Follow EPA Guidelines.
EPA Guidelines. Some water bodies have been tested and fish have been found to have low mercury lev-
els. For these locations, and for locations where data is limited or not available, DOH recommends following
guidelines set by the U.S. Environmental Protection Agency (EPA). These guidelines are summarized here:
EPA advisories cover all water bodies in the United States and apply only to fish caught by you, your fam-
ily, and friends. They recommend the following:
• Women who are pregnant or may become pregnant, and nursing mothers should, in a week’s time, eat
no more than 8 ounces of fish caught by themselves, family, and friends.
• Children under age 10 should, in a week’s time, eat no more than 3 ounces of fish caught by themselves,
family and friends.
More information on EPA advisories is online at www.epa.gov/waterscience/fishadvice/advice.html
FDA advises that women of childbearing age and pregnant women may, each week, eat an average of 12
ounces of fish purchased in stores and restaurants. Therefore, if in a given week you eat 12 ounces of
cooked fish from a store or restaurant, then do not eat any fish caught by family or friends that week. This
is necessary in order to keep the total level of methyl mercury contributed by all fish at a low level in your
body. More information regarding FDA advisories is online at www.cfsan.fda.gov/~dms/admehg.html
DOH is not constrained by a fixed numerical mercury level and can deviate from those listed above
based on DOH’s best professional judgment.
above the lateral line and anterior to the origin of the
first dorsal fin. White muscle tissue taken from this
region is representative of the portion of fish con-
sumed by humans. Care was taken to assure that the
sample made no contact with epidermal or dermal
layers, scales, or other surrounding surfaces during the
extraction process. Tissue samples were immediately
placed in sterile polyethylene vials and frozen at –20°C
until analyzed. Before analysis, tissue samples were
digested using standard procedures in accord with
EPA Method 245.1 to convert all mercury in the sam-
ple to Hg(II) (EPA, 1991; Frick, 1996). The mercury in
each digested sample was reduced to elemental mer-
cury by reaction with excess stannous chloride. This
elemental mercury [Hg(0)] was purged from solution
in a gas-liquid separator and swept into an atomic
absorption spectrometer for detection and quantifi-
cation by cold vapor atomic absorption spectrometry
following standardized procedures (EPA, 1991; Booe-
shahgi et al., 1995) at the DEP Chemistry Laboratory.
Quality control measures included analysis of labo-
ratory method blanks, duplicate or triplicate tissue
samples, duplicate matrix spikes, and standard fish-
tissue reference material (DORM-1 or DOLT-2,
FMRI Technical Report TR-9 3
Mercury Levels in Marine and Estuarine Fishes of Florida 1989–2001 Adams et al.
obtained from the National Research Council of Cana-
da) for each group of 20 or fewer fish samples analyzed
(EPA, 1991; Frick, 1996; T.Chandrasekhar,DEP, personal
communication). All total mercury levels are reported
as parts per million (ppm) wet weight. Linear regres-
sions were used to describe relationships between fish
size and total mercury concentration. Mercury data
used in regressions were log transformed when appro-
priate to meet homoscedasticity requirements.
Differences in the sizes of fish from three or more
study areas were examined by using a Kruskal-Wallis
test; a Mann-Whitney Rank Sum test was used when
sizes of fish from only two study areas were compared.
We used a t-test or Mann-Whitney Rank Sum test, as
appropriate, to test for significant differences in the total
mercury levels of males and females of selected fish
species. We also used a t-test or Mann-Whitney Rank
Sum test to determine whether there were significant
differences in the lengths of males and females of
selected fish species.
Results and Discussion
From April 1989 to May 2001, a total of 6,806 fish rep-
resenting 108 species from 40 families were collected
from Florida estuaries and adjacent coastal waters for
mercury analysis. Species represented all major troph-
ic groups, ranging from primary consumers to apex
predators (species that occupy the highest trophic lev-
els). A total of 2,023 fish, representing 68 species, were
collected from the Indian River Lagoon and adjacent
waters; 1,661 fish, representing 58 species, were col-
lected from Tampa Bay and adjacent waters; 905 fish,
representing 49 species, were collected from Florida
Keys/Florida Bay; 594 fish, representing 45 species,
were collected from Charlotte Harbor; 435 fish, repre-
senting 16 species, were collected from Cedar Key;
246 fish, representing 12 species, were collected from
Apalachicola Bay; 228 fish, representing 23 species,
were collected from Choctawhatchee Bay; 212 fish,
representing 16 species, were collected from north-
east Florida; 205 fish, representing 28 species, were
collected from Volusia County waters; and 204 fish,
representing 15 species, were collected from Teques-
ta/southern Indian River Lagoon. The remainder of
the fish were collected from Everglades coastal waters,
Sarasota Bay, and nearshore and offshore waters along
the Atlantic and gulf coasts of Florida.
Results of mercury analyses of species with total
sample sizes greater than or equal to 40 fish are dis-
cussed below. Species are presented in phylogenetic
order according to Nelson (1984) and Robins et al.
(1991). Summary results for all species, regardless of
sample size, are presented in the Appendix Table.
Bull shark
Carcharhinus leucas
The bull shark, Carcharhinus leucas, is an apex preda-
tor that inhabits estuarine, nearshore, and offshore
waters of both the gulf and Atlantic coasts of Florida.
Bull sharks commonly enter estuarine waters and are
one of the only shark species to penetrate far into
freshwater habitats (Thorson, 1971, 1972; Thomerson
and Thorson, 1977). Adult females give birth to 1–13
pups in estuarine waters during the spring and sum-
mer months (Compagno, 1984). Along the Atlantic
coast of Florida, juveniles use coastal lagoon habitats
for up to several years (Snelson et al., 1984; FWC-FMRI,
unpublished data). Females of this species mature at
approximately 18+ years and males at 14–15 years; the
maximum estimated age for bull sharks in the north-
ern Gulf of Mexico is 24.2 years (Branstetter and Stiles,
1987). Based on preliminary results, the maximum
unvalidated age estimate for this species in Atlantic
waters of the southeastern United States is 26 years
(NMFS/FWC-FMRI, unpublished data). In Florida
waters, bull sharks feed on a wide variety of fishes
and, to a lesser degree, on crabs and shrimps (Dodrill,
1977; Snelson et al., 1984; D. Adams, unpublished data).
This shark is landed as part of the commercial
shark fishery for large coastal species and is also fre-
quently caught by recreational shark fishermen in
many areas (Branstetter,1986; NMFS, 1993).There is a
seasonal recreational fishery for juvenile bull sharks in
the Indian River Lagoon system (Adams, 1995) and in
other estuaries in Florida. There is no size limit for
bull sharks, but the current recreational bag limit in
Florida is one per person per day or 2 per vessel per
day, whichever is less.
Bull sharks analyzed for mercury were collected
from the Indian River Lagoon (n = 55), Charlotte Har-
bor (n = 3), and Tampa Bay (n = 1).These 59 bull sharks
were juveniles and ranged from 552 to 1,075 mm pre-
caudal length (PCL).Total mercury levels for individual
fish ranged from 0.24 to 1.70 ppm (Appendix Table). The
mean total mercury level for fish from the Indian River
Lagoon was 0.78 ppm (median = 0.74 ppm) and in
those from Charlotte Harbor was 0.97 ppm (median =
1.20 ppm), both of which were greater than 0.5 ppm.
4 FMRI Technical Report TR-9
Adams et al. Mercury Levels in Marine and Estuarine Fishes of Florida 1989–2001
Approximately 82% of all bull sharks from the Indian
River Lagoon tested had total mercury levels greater
than or equal to 0.5 ppm. Three bull sharks collected
from this area contained total mercury levels greater
than or equal to 1.5 ppm.
Analysis of bull sharks from the Indian River
Lagoon revealed a significant positive correlation
between total mercury level and fish length (P < 0.001),
indicating that mercury levels tend to increase as bull
sharks grow. In May 1991, the Florida Department of
Health (DOH) released a health advisory urging lim-
ited consumption of all shark species from Florida
waters. Because mercury concentrations were in excess
of U.S. Food and Drug Administration and state stan-
dards, DOH recommended that adults should eat
shark no more than once a week, and children and
women of childbearing age should eat shark no more
than once a month. (HRS, 1991: p. 2). In January 2003,
DOH issued an updated health advisory recom-
mending no consumption of large sharks (>43 inches,
or approximately 1,090 mm TL), and limited con-
sumption of sharks less than 43 inches TL (DOH, 2003).
Blacktip shark
Carcharhinus limbatus
The blacktip shark, Carcharhinus limbatus, inhabits
estuarine, nearshore, and offshore waters of both the
gulf and Atlantic coasts of Florida. Florida estuaries
serve as important nursery habitats for this species
(FWC-FMRI, 1991–2000). Adult females have a one-year
gestation period and give birth to 1–10 pups during the
spring and summer months (Compagno, 1984). The
complete reproductive cycle, including biennial ovu-
lation, lasts two years (Castro, 1995). Females of this
species mature at approximately 6–7 years and the
males at 4–6 years; blacktip sharks have a maximum
age of 11 years (Killam and Parsons, 1989; Wintner and
Cliff, 1996).This species feeds on a variety of fishes and,
to a lesser degree, on crabs and other invertebrates
(Bass et al., 1973; Dodrill, 1977; Dudley and Cliff, 1993).
This apex predator supports major commercial
and recreational fisheries throughout Florida. It is
frequently landed as a major component of the com-
mercial fishery for large coastal sharks and composes
a substantial proportion of the recreational shark catch
in many areas (Parrack, 1990; NMFS, 1993, 2000). Black-
tip sharks, along with sandbar sharks, C. plumbeus, are
frequently targeted because of the quality and high
market value of their meat and fins (NMFS, 1993;
Brown, 1999; Shotton, 1999). There is no size limit for
blacktip sharks, but the current recreational bag limit
in Florida is one per person per day or 2 per vessel per
day, whichever is less.
Mercury levels detected in individual blacktip
sharks from Florida waters were often greater than
0.5 ppm. Blacktip sharks used in the mercury analyses
were collected from Tampa Bay, the Indian River
Lagoon and adjacent offshore waters, Charlotte Har-
bor, and Florida Keys/Florida Bay. Most of the 98
blacktip sharks were juveniles and smaller adults
(405–1,510 mm PCL), but 4 embryos (ranging 223–235
mm PCL) were also analyzed. Total mercury levels in
individual fish ranged from 0.03 to 2.60 ppm. Total
mercury levels in 4 embryos collected from a single
1,050-mm-PCL female whose total mercury level was
2.30 ppm, ranged from 0.63 to 0.78 ppm (mean = 0.69
ppm; median = 0.68 ppm) (Adams and McMichael,
1999). Comparisons of pregnant females and their
associated embryos in this and related species indicate
that transmission of mercury from maternal sources
may be an important factor in accumulation of mercury
in shark muscle tissue (Adams and McMichael, 1999).
The mean total mercury level in each of the study
areas was greater than 0.5 ppm; these mean levels
ranged from a minimum of 0.54 ppm in Tampa Bay
(median = 0.47 ppm) to a maximum of 1.84 ppm in Flori-
da Keys/Florida Bay (median = 1.85 ppm). Similar
mercury levels have been documented for blacktip
sharks in Australian coastal waters (Lyle, 1984, 1986).
Analysis of blacktip sharks from Tampa Bay and the
Indian River Lagoon and adjacent offshore waters
revealed a significant positive correlation between
total mercury level and blacktip shark length (P <
0.0001), indicating that mercury levels tend to increase
as blacktip sharks grow.
In May 1991, the Florida Department of Health
(DOH) released a health advisory urging limited con-
sumption of all shark species from Florida waters.
Because mercury concentrations were in excess of U.S.
Food and Drug Administration and state standards,
DOH recommended that adults should eat shark no
more than once a week, and children and women of
childbearing age should eat shark no more than once
a month. (HRS, 1991: p. 2). In January 2003, DOH issued
an updated health advisory recommending no con-
sumption of large sharks (>43 inches, or approximately
1,090 mm TL), and limited consumption of sharks less
than 43 inches TL (DOH, 2003).
FMRI Technical Report TR-9 5
Mercury Levels in Marine and Estuarine Fishes of Florida 1989–2001 Adams et al.
Atlantic sharpnose shark
Rhizoprionodon terraenovae
The Atlantic sharpnose shark, Rhizoprionodon terraen-
ovae, is a common species that inhabits estuarine,
nearshore, and offshore waters of the gulf and Atlantic
coasts of Florida. Adult females have a 10- to 11-month
gestation period and give birth to pups during the late
spring and summer (Parsons, 1983). This species
matures at approximately 2.4–3.9 years (Parsons, 1985)
and lives for up to 8–10 years in the Gulf of Mexico
(Branstetter, 1987). In the southeastern U.S. Atlantic,
sexual maturity is attained at 3 years and the maximum
age is 11+ years (Loefer and Sedberry, 2003). Atlantic
sharpnose sharks feed on a variety of fishes, crabs,
and shrimp (Clark and von Schmidt, 1965; D. Adams,
unpublished data).
This species is commonly caught by recreational
shark fishermen (Parrack, 1990; NMFS, 1993). The
Atlantic sharpnose shark is a major component of the
U.S. Atlantic commercial fishery for small coastal shark
species. It is routinely landed both recreationally and
commercially on the Atlantic coast of Florida in the
Cape Canaveral region (D. Adams, personal observa-
tion) and is discarded in large numbers during shrimp
trawling operations (NMFS, 1993).This species is also
frequently caught in the Gulf of Mexico during long-
line fishing operations that target other shark species
(Russell, 1993).There is no size limit for Atlantic sharp-
nose sharks, but the current recreational bag limit in
Florida is one per person per day or two per vessel per
day, whichever is less.
Most of the Atlantic sharpnose sharks analyzed
were collected from nearshore and offshore waters of
the Atlantic coast of Florida adjacent to the Indian
River Lagoon system (n = 81), and a limited number
were collected from Volusia County offshore waters (n
= 4). Mercury levels detected in Atlantic sharpnose
sharks from Florida’s Atlantic coast waters were usu-
ally high. Precaudal lengths (PCL) of the 85 juvenile and
adult Atlantic sharpnose sharks collected ranged from
220 to 857 mm.Total mercury levels for individual fish
from offshore waters of the Atlantic coast of Florida
adjacent to the Indian River Lagoon system ranged
from 0.11 to 2.30 ppm.The mean total mercury level was
1.06 ppm, and the median was 0.95 ppm (Appendix
Table). Similar mercury levels were found in Aus-
tralian sharpnose sharks, Rhizoprionodon taylori, and
milk sharks, R. acutus, from Australian waters (Lyle,
1986). Of the 85 juvenile and adult Atlantic sharpnose
sharks tested from Florida waters, approximately 71%
had total mercury levels greater than or equal to 0.5
ppm. Approximately 28% of juvenile and adult Atlantic
sharpnose sharks tested from Florida waters contained
total mercury levels greater than or equal to 1.5 ppm.
Total mercury levels in six embryos from pregnant
female Atlantic sharpnose sharks collected from off-
shore waters of the Atlantic coast of Florida adjacent
to the Indian River Lagoon system ranged from 0.17 to
0.29 ppm (mean = 0.22 ppm; median = 0.19 ppm).
Atlantic sharpnose shark embryos analyzed ranged
from 74 to 85 mm PCL. Mercury levels in Atlantic
sharpnose shark embryos within each litter were sim-
ilar and ranged from 8.3% to 15.3% of the total mercury
levels in their respective mothers (Adams and
McMichael, 1999).
Analysis of Atlantic sharpnose sharks from off-
shore waters of the Atlantic coast of Florida adjacent
to the Indian River Lagoon system revealed a signifi-
cant positive correlation between total mercury level
and fish length (P < 0.0001).Total mercury level in this
species increases as individuals grow. Total mercury lev-
els for larger sharks (>500 mm PCL) were usually high
(>0.5 ppm). Although precaudal lengths of females
examined in this study were significantly larger than
those of males (t-test, P < 0.05), total mercury levels for
females and males were not significantly different
(Mann-Whitney rank sum test, P > 0.1).
In May 1991, the Florida Department of Health
(DOH) released a health advisory urging limited con-
sumption of all shark species from Florida waters.
Because mercury concentrations were in excess of U.S.
Food and Drug Administration and state standards,
DOH recommended that adults should eat shark no
more than once a week, and children and women of
childbearing age should eat shark no more than once
a month (HRS, 1991: p. 2). In January 2003, DOH issued
an updated health advisory recommending no con-
sumption of large sharks (>43 inches, or approximately
1,090 mm TL) and limited consumption of sharks less
than 43 inches TL (DOH, 2003).
Bonnethead shark
Sphyrna tiburo
6 FMRI Technical Report TR-9
Adams et al. Mercury Levels in Marine and Estuarine Fishes of Florida 1989–2001
The bonnethead shark, Sphyrna tiburo, is common in
coastal waters of Florida. This species of small ham-
merhead shark is frequently caught by recreational
fishermen and is landed as part of the commercial
fishery for small coastal shark species (Parrack, 1990;
NMFS, 1993). There is no size limit for bonnethead
sharks, but the current recreational bag limit in Flori-
da is one per person per day or two per vessel per
day, whichever is less.
This predator inhabits estuarine, nearshore, and
offshore waters of both the gulf and Atlantic coasts of
Florida.The gestation period for this species is approx-
imately 4–5 months (Parsons, 1993a)—the shortest
known gestation period of any placental viviparous
shark species (G. Parsons, University of Mississippi,
personal communication). Females give birth to 4–16
pups (Compagno, 1984). This species matures at
approximately 2 years of age and is estimated to live
7+ years (Parsons, 1993b). Bonnethead sharks feed
principally on crabs, shrimps, and other invertebrates
(Parsons, 1987; Cortes et al., 1996; D. Adams, unpub-
lished data).
Bonnethead sharks used in the mercury analyses
were collected from the Indian River Lagoon and adja-
cent offshore waters, Tampa Bay, Charlotte Harbor,
Choctawhatchee Bay, and Florida Keys/Florida Bay.
The 213 bonnethead sharks sampled ranged from 206
to 1,081 mm PCL. The majority of samples were col-
lected from the Indian River Lagoon and adjacent
offshore waters (n = 137). Included with the juvenile and
adult bonnethead sharks examined from this area
were 41 near-term embryos (206 to 255 mm PCL). Mer-
cury levels detected in bonnethead sharks from Florida
waters were often greater than 0.5 ppm.Total mercury
levels for individual fish ranged from 0.03 to 1.60 ppm
(Appendix Table). The mean total mercury levels ranged
from a minimum of 0.34 ppm for fish in Charlotte Har-
bor (median = 0.27 ppm) to a maximum of 1.14 ppm for
fish in Florida Keys/Florida Bay (median = 1.20 ppm).
Total mercury levels for juvenile and adult bonnet-
head sharks (results from embryos not included) from
the Indian River Lagoon and adjacent offshore waters
(297–1081 mm PCL) ranged from 0.13 to 1.5 ppm (mean
= 0.50 ppm; median = 0.29 ppm).Total mercury levels
for the 41 embryos examined ranged from 0.08 to 0.35
ppm (mean = 0.16 ppm; median = 0.13 ppm). Total
mercury levels in embryos of this species equaled
9.1%–60.4% of levels observed in their respective moth-
ers (Adams and McMichael, 1999).
Analysis of bonnethead sharks from the Indian
River Lagoon and adjacent offshore waters revealed a
significant positive relationship between total mercury
level and fish length (P < 0.0001), indicating that mer-
cury levels tend to increase as bonnethead sharks grow.
The relationship between total mercury level and fish
length was not as strong for bonnethead sharks collected
from Tampa Bay (P > 0.001), but it also indicated that
mercury levels increase as individuals grow.
In May 1991, the Florida Department of Health
(DOH) released a health advisory urging limited con-
sumption of all shark species from Florida waters.
Because mercury concentrations were in excess of U.S.
Food and Drug Administration and state standards,
DOH recommended that adults should eat shark no
more than once a week, and children and women of
childbearing age should eat shark no more than once
a month. (HRS, 1991: p. 2). In January 2003, DOH issued
an updated health advisory recommending no con-
sumption of large sharks (>43 inches, or approximately
1,090 mm TL), and limited consumption of sharks less
than 43 inches TL (DOH, 2003).
Atlantic stingray
Dasyatis sabina
The Atlantic stingray, Dasyatis sabina, is found in estu-
arine and nearshore waters along Florida’s Atlantic
and gulf coasts, where they inhabit a range of estuar-
ine and nearshore habitats, including seagrass flats,
open-sand flats, mud flats, and channels or basins
(Schwartz and Dahlberg, 1978; FWC-FMRI, 1991–2000).
This species also enters freshwater habitats (Gunter,
1938a), and a permanent freshwater population has
been documented in the St. Johns River on the Atlantic
coast of Florida (Tagatz, 1968; Johnson and Snelson,
1996).The mating season for Atlantic stingrays in Flori-
da waters extends from October through March (Lewis,
1982; Snelson et al., 1988; Johnson and Snelson, 1996).
Although age and growth studies have been attempt-
ed (Schmid, 1988), little is known regarding age or
growth rate of this species. This species feeds princi-
pally on invertebrate prey such as amphipods, mysids,
and mollusks (Cook, 1994).
This abundant species is not routinely pursued
by commercial or recreational fishermen, but it is occa-
FMRI Technical Report TR-9 7
Mercury Levels in Marine and Estuarine Fishes of Florida 1989–2001 Adams et al.
sionally harvested for human consumption or to be
used as shark or crab bait. Atlantic stingrays are fre-
quently caught as bycatch in many fisheries operating
in Florida waters.
Atlantic stingrays used in the mercury analyses
were principally collected from the Indian River Lagoon
(n = 35), but a limited number of samples were also col-
lected from Charlotte Harbor (n = 9), Choctawhatchee
Bay (n = 6), northeast Florida (n = 4), and Tampa Bay
(n = 4).The 58 Atlantic stingrays collected ranged from
94 to 329 mm disk width. Disk widths of female and
male Atlantic stingrays examined in this study were not
significantly different (Mann-Whitney rank sum test,
P > 0.1). Mercury levels detected in Atlantic stingrays
were usually low.Total mercury levels for individual fish
ranged from 0.01 to 0.54 ppm (Appendix Table). The
mean total mercury level for fish in the Indian River
Lagoon, where the majority of samples were collect-
ed, was 0.16 ppm, and the median was 0.16 ppm. When
we analyzed the relationship between mercury level
and size of Atlantic stingray from the Indian River
Lagoon, we found a significant positive correlation
between total mercury level and disk width (P < 0.001),
indicating that mercury levels tend to increase as
Atlantic stingrays grow.Total mercury levels in females
and males were not significantly different (t-test, P >
0.1). Only one Atlantic stingray collected from Florida
waters contained a total mercury level greater than or
equal to 0.5 ppm.
Ladyfish
Elops saurus
The ladyfish, Elops saurus, inhabits estuarine,
nearshore, and coastal waters of the gulf and Atlantic
coasts of Florida.There may be more than one species
or stock of ladyfish in Florida waters (Smith, 1990;
Schmid, 1992; McBride et al., 2001), and further
research is currently being conducted by FWC-FMRI
scientists to answer this question. Ladyfish spawn in
fall and spring, probably offshore (Zale and Merrifield,
1989), and larval and juvenile ladyfish are frequent-
ly collected in a variety of Florida estuarine habitats
(FWC-FMRI, 1991–2000; McBride et al., 2001). Little is
known regarding the age and growth of this species
(Zale and Merrifield, 1989). Ladyfish feed principal-
ly on midwater fishes and decapod crustaceans (Dar-
nell, 1958; Sekavec, 1974).
Ladyfish are frequently caught by recreational
fishermen, and the species supports a commercial
fishery throughout Florida. In 2000, approximately
498,000 pounds of ladyfish were landed from Florida
waters (Murphy et al., 2001). The majority (98%) of
Florida’s ladyfish landings are from the commercial
fishery along the gulf coast.The recreational fishery in
Florida catches more than 2,000,000 fish each year, but
only 5%–10% are actually retained (Murphy and Muller,
1998; Murphy et al., 2000).
The 218 ladyfish used in the mercury analyses
were collected in Tampa Bay, the Indian River Lagoon,
Charlotte Harbor, Florida Keys/Florida Bay,
Choctawhatchee Bay, Cedar Key, and, Apalachicola
Bay; they ranged from 115 to 580 mm standard length
(SL). Total mercury levels for individual fish ranged
from 0.02 to 2.60 ppm. The mean total mercury levels
varied by study area (Appendix Table). Mean total
mercury levels were higher for fish from the Indian
River Lagoon (mean = 0.72 ppm; median = 0.56 ppm)
and Tampa Bay (mean = 0.52 ppm; median = 0.42 ppm)
than for fish from Charlotte Harbor (mean = 0.34 ppm;
median = 0.23 ppm) and Apalachicola Bay (mean = 0.09
ppm; median = 0.06 ppm).The comparatively lower lev-
els detected in ladyfish from Charlotte Harbor may be
related to the fact that ladyfish collected from Charlotte
Harbor were significantly smaller than those collect-
ed from the Indian River Lagoon or Tampa Bay
(Kruskal-Wallis test, P < 0.01; Dunn’s method, P < 0.05).
Ladyfish collected in Apalachicola Bay contained lower
overall mercury levels than did the ladyfish collected
in any of the other Florida sampling areas; however, fish
sampled from Apalachicola Bay were significantly
smaller (mean = 258 mm SL) than those collected in the
Indian River Lagoon (mean = 373 mm SL),Tampa Bay
(mean = 350 mm SL), and Charlotte Harbor (mean =
317 mm SL) (Kruskal-Wallis test, P < 0.01; Dunn’s
method, P < 0.05).
Analysis of ladyfish from the Indian River Lagoon,
Charlotte Harbor, and Apalachicola Bay revealed a
significant positive correlation between total mercury
level and length of fish (P < 0.0001), and analysis of lady-
fish from Tampa Bay revealed a weak positive
correlation (P < 0.01).The positive correlation between
total mercury level and fish length in each study area
indicates that mercury levels tend to increase as lady-
fish in Florida grow. Mercury levels for ladyfish
collected in all study areas were variable; however, in
most areas, a high percentage of the fish in the larger
size-classes (≥380 mm SL) had mercury levels greater
than or equal to 0.5 ppm (Tampa Bay = 73%; Charlotte
Harbor = 63%; Indian River Lagoon = 100%). Only
8 FMRI Technical Report TR-9
Adams et al. Mercury Levels in Marine and Estuarine Fishes of Florida 1989–2001
three fish collected from Apalachicola Bay were greater
than 380 mm SL, and none of these had mercury lev-
els greater than or equal to 0.5 ppm.
After reviewing these results, the Florida Depart-
ment of Health released a health advisory on 6 October
1995 urging limited consumption of ladyfish from Tampa
Bay and the Indian River Lagoon (HRS, 1995: p. 2).
Hardhead catfish
Arius felis
Hardhead catfish, Arius felis, are abundant in estuar-
ine and nearshore coastal waters throughout Florida.
Hardhead catfish spawn in estuarine habitats from
May to August (Jones et al., 1978), and males carry
developing eggs and juveniles in their mouths during
this time (Ward, 1957). After leaving the protection of
the male’s mouth, juvenile hardhead catfish occupy a
wide range of estuarine habitats (FWC-FMRI,
1991–2000; Adams & Tremain, 1995). Adults inhabit
estuaries or nearshore waters, and a portion of the
adult population may migrate offshore during winter
months to avoid the low temperatures of inshore waters
(Muncy and Wingo, 1983; FWC-FMRI, 1994, 1995; FWC-
FMRI Nearshore Gillnet Survey, unpublished). This
species often concentrates near thermal effluent plumes
of coastal power plants (Gallaway and Strawn, 1974;
FWC-FMRI, unpublished data). Hardhead catfish reach
sexual maturity at approximately 2 years of age (Ben-
son, 1982). Doermann et al. (1977) reported a maximum
age of 5–8 years, but recent research at FWC-FMRI indi-
cates that the maximum age for this species may be 20
years or more.
Hardhead catfish are opportunistic omnivores that
feed on algae, seagrasses, coelenterates, polychaetes,
crustaceans, small fishes, and occasionally human
garbage (Merriman, 1940). Diets of hardhead catfish
and gafftopsail catfish, a related species, are similar
(Merriman, 1940). Gunter (1945), Darnell (1961), Gall-
away and Strawn (1974), and others have reported that
blue crabs were common in the diet of this species.
This demersal species is frequently encountered
by recreational and commercial fishermen. It is land-
ed as bycatch during a variety of inshore and nearshore
commercial fishing operations. The Indian River
Lagoon is the area of highest commercial landings for
this species (Murphy and Muller, 1995). Although it is
not favored as a food fish, recreational fishermen occa-
sionally land hardhead catfish and commercial
fishermen mix large hardhead catfish with gafftopsail
catfish, Bagre marinus, landings for use as food fish.
Hardhead catfish were principally collected from
Ta mpa Bay, the Indian River Lagoon, and Choctaw-
hatchee Bay. A total of seven samples were also
collected in Charlotte Harbor. The 45 hardhead cat-
fish analyzed for total mercury levels ranged from 210
to 390 mm standard length. Mercury levels detected
in hardhead catfish from Florida waters were usual-
ly low.Total mercury levels for individual fish ranged
from 0.02 to 0.50 ppm. The mean total mercury lev-
els for hardhead catfish were low in all study areas,
ranging from 0.15 (median = 0.12 ppm) for fish from
the Indian River Lagoon to 0.23 (median = 0.23 ppm)
for those from Choctawhatchee Bay. Only one hard-
head catfish tested from Florida waters (collected in
Ta mpa Bay) had a total mercury level equal to 0.5
ppm, and no individuals contained levels greater
than this level.
Gafftopsail catfish
Bagre marinus
Gafftopsail catfish, Bagre marinus, is a demersal species
that inhabits estuarine and nearshore waters of the gulf
and Atlantic coasts of Florida. Gafftopsail catfish spawn
over inshore mud flats from May to August (Jones et
al., 1978), and males carry developing eggs and juve-
niles in their mouths during this time (Ward, 1957).
Feeding by males carrying eggs or juveniles has not
been documented. After leaving the protection of the
male’s mouth, juvenile gafftopsail catfish commonly
inhabit channels and basins within estuaries (FWC-
FMRI, 1991–2000). Juveniles and larger subadults may
also move into nearshore continental shelf waters
(Gunter, 1938b). Adults inhabit estuaries and nearshore
shelf waters (Muncy and Wingo, 1983; FWC-FMRI,
1991–2000; FWC-FMRI Nearshore Gillnet Survey,
unpublished). Gafftopsail catfish reach sexual matu-
rity before 2 years of age (Benson, 1982).
Gafftopsail catfish are opportunistic omnivores
FMRI Technical Report TR-9 9
Mercury Levels in Marine and Estuarine Fishes of Florida 1989–2001 Adams et al.
that feed on algae, seagrasses, coelenterates, poly-
chaetes, crustaceans, small fishes, and occasionally
human garbage (Merriman, 1940). Gunter (1945), Dar-
nell (1961), Gallaway and Strawn (1974), and others
have reported that blue crabs were common in the
diet of this species.
Gafftopsail catfish are commonly encountered by
recreational and commercial fishermen throughout
Florida. In the minor commercial fishery that this
species supports, it is landed as bycatch during a vari-
ety of inshore and nearshore fishing operations. Most
of the commercial landings of this species are from the
Indian River Lagoon (Murphy and Muller, 1995). Recre-
ational fishermen occasionally land gafftopsail catfish
as a food fish.
Gafftopsail catfish used in the mercury analyses
were principally collected from Tampa Bay (n = 59)
and the Indian River Lagoon (n = 11). A smaller num-
ber of samples were also collected in Charlotte Harbor
(n = 4) and Choctawhatchee Bay (n = 4).The 78 gafftop-
sail catfish analyzed ranged from 115 to 528 mm
standard length (SL). Mercury levels detected in
gafftopsail catfish from Florida estuarine waters were
variable; however, levels in larger fish were often
greater than or equal to 0.5 ppm.Total mercury levels
for individual fish ranged from 0.02 to 1.80 ppm. The
mean total mercury level for this species in Tampa Bay
was 0.60 ppm and the median was 0.54 ppm.The mean
total mercury level for fish from the Indian River
Lagoon was 0.33 ppm and the median was 0.38 ppm.
The higher mean total mercury level observed in fish
from Tampa Bay may be due, in part, to the larger
mean size of gafftopsail catfish tested from this region.
The mean standard length of fish examined from
Ta mpa Bay (374 mm SL) was greater than that of fish
from the Indian River Lagoon (302 mm SL).
Analysis of gafftopsail catfish from Tampa Bay
indicated a positive correlation between total mercury
level and fish length (P < 0.01). Mercury levels of
gafftopsail catfish collected in Tampa Bay were variable,
but mercury levels of larger fish (>350 mm SL) were
often greater than or equal to 0.5 ppm.
After reviewing these results, the Florida Depart-
ment of Health released a health advisory on 6 October
1995 (HRS, 1995: p. 2) urging limited consumption of
gafftopsail catfish from Tampa Bay waters. Mercury
levels in gafftopsail catfish from other Florida study
areas (the Indian River Lagoon, Choctawhatchee Bay,
Florida Keys/Florida Bay) were considered “potential-
ly problematic”(HRS, 1995: p. 3).
In January 2003, DOH issued an updated health
advisory recommending limited consumption of
gafftopsail catfish from Choctawhatchee Bay and Tampa
Bay (DOH, 2003).
Figure 2. Relationship between ln total mercury level (ppm) and
standard length (mm) of common snook, Centropomus undec-
imalis, from Tampa Bay, Florida. The dashed line represents the
antilog equivalent of the 0.5-ppm threshold level.
Common snook
Centropomus undecimalis
Common snook, Centropomus undecimalis, inhabit man-
grove-fringed bays, marshes, tidal creeks, and other
estuarine habitats as adults and juveniles (Gilmore et
al., 1983; McMichael et al., 1989; FWC-FMRI, 1992).
Adults are also found in inlet and nearshore waters dur-
ing the warmer months. Adult common snook tend to
migrate seaward, moving out through inlets and pass-
es during the spawning season (Volpe, 1959). Spawning
occurs from April to October near inlets and coastal
passes. Common snook on Florida’s Atlantic and gulf
coasts form two genetically distinct stocks (Tringali
and Bert, 1996). Common snook inhabiting the Atlantic
coast grow faster and to a larger size than do those from
the gulf coast (Taylor et al., 1993, 2000). This species
can live up to 21 years (Taylor et al., 2000). Growth rates
are variable, and females typically grow to larger sizes
and live longer than males do. Common snook are
protandric hermaphrodites; males develop into females
between the ages of 2 and 7 years (Taylor and Grier,
1991). Females less than 444 mm SL are not common-
ly encountered (Taylor et al., 2000). Snook are
10 FMRI Technical Report TR-9
Adams et al. Mercury Levels in Marine and Estuarine Fishes of Florida 1989–2001
Figure 3. Relationship between ln total mercury level (ppm) and
standard length (mm) of common snook, Centropomus undec-
imalis, from Florida Keys/Florida Bay, Florida. The dashed line
represents the antilog equivalent of the 0.5-ppm threshold level.
opportunistic predators that feed on a wide variety of
fishes and crustaceans (Seaman and Collins, 1983).
The common snook is one of Florida’s premier
gamefish. In 2000, 75,059 common snook, weighing a
total of approximately 593,849 pounds, were recre-
ationally landed from Florida waters. Landings were
slightly higher (52% by weight; 54% by number of fish)
on the gulf coast than on the Atlantic coast of Florida
during 2000 (Murphy et al., 2001). Commercial harvest
of snook was abolished in 1957 to reduce overall
exploitation rates (Volpe, 1959). Because of a continued
decline in snook populations caused by recreational
fishing pressure and habitat degradation, recreation-
al harvest restrictions were implemented in 1985.
Common snook were collected from representa-
tive habitats in Tequesta/southern Indian River Lagoon,
Ta mpa Bay, Florida Keys/Florida Bay, the Indian River
Lagoon, Charlotte Harbor, and the Everglades. One fish
was also collected from the Cedar Key area. The 424
common snook analyzed for total mercury levels
ranged from 168 to 867 mm SL.Total mercury levels for
individual fish ranged from 0.03 to 1.80 ppm (Appen-
dix Table). Mercury levels detected in common snook
from Florida estuarine waters were variable, and
regional differences were detected.Total mercury lev-
els in fish from the Atlantic coast, the gulf coast, and
Florida Keys/Florida Bay were significantly different
(Kruskal-Wallis test, P < 0.0001; Dunn’s method, P <
0.05). Mean total mercury levels were similar for gulf
coast fish from Tampa Bay (0.39 ppm; median = 0.34
ppm) and Charlotte Harbor (0.37 ppm; median = 0.36
ppm).The mean total mercury levels for Atlantic coast
snook from Tequesta/southern Indian River Lagoon
(0.22 ppm; median = 0.21 ppm) and the Indian River
Lagoon (0.22 ppm; median = 0.21 ppm) were the same.
Mercury levels in snook from the Florida Keys/Flori-
da Bay (mean = 0.60 ppm; median = 0.51 ppm) and from
the Everglades (mean = 0.63 ppm; median = 0.57 ppm)
were significantly higher than levels from all other
areas (Kruskal-Wallis test, P < 0.0001; Dunn’s method,
P < 0.05). The relatively low mean level detected in
common snook from the Florida Atlantic coast may be
related to the smaller size of fish collected in that area.
Common snook collected from the Atlantic coast
(262–745 mm SL; mean = 433 mm SL) were signifi-
cantly smaller than those sampled from the gulf coast
(168–867 mm SL; mean = 482 mm SL) and Florida
Keys/Florida Bay (333–860 mm SL; mean = 574 mm SL)
(Kruskal-Wallis test, P < 0.0001; Dunn’s method, P <
0.05). Differences in mercury levels in fish from the
Atlantic coast and those from the gulf coast of Florida
may also be influenced by the differences in growth
rates observed for these two distinct snook populations.
Significant positive correlations between total mer-
cury level and fish length were detected for common
snook collected from Tampa Bay (P < 0.0001) (Figure 2)
and Florida Keys/Florida Bay (P < 0.0001) (Figure 3).
Analyses of this species from Indian River Lagoon (P
> 0.001), Tequesta/southern Indian River Lagoon (P >
0.01), and Charlotte Harbor (P > 0.01) showed com-
paratively weaker correlations between total mercury
level and fish length. When common snook were
pooled by Atlantic coast (Indian River Lagoon and
Tequesta/southern Indian River Lagoon) and gulf coast
(Tampa Bay and Charlotte Harbor) populations, there
was a stronger relationship between total mercury
level and fish length for gulf coast fish (P < 0.0001; r2=
0.254) than for Atlantic coast fish (P > 0.001; r2 = 0.057).
Approximately 27% of all common snook from
Florida waters had levels greater than or equal to 0.5
ppm. Although there was considerable variation, fish
with mercury levels greater than or equal to 0.5 ppm
(n = 91; 359–867 mm SL) were significantly larger than
those with levels below 0.5 ppm (n = 333; 168–775 mm
SL) (Mann-Whitney rank sum test, P < 0.0001).
A total of 103 common snook collected from Flori-
da waters were within the legal or harvestable “slot
limit” (approximately 547–721 mm SL; 660–864 mm
TL). Approximately 44% of common snook within the
legal “slot limit”had levels greater than or equal to 0.5
ppm, but only the Florida Keys/Florida Bay and the
Everglades areas had “slot-limit” snook with mean
total mercury levels greater than 0.5 ppm. Of com-
mon snook larger than the “slot limit”(n = 15), all but
two fish had mercury levels greater than 0.5 ppm.
In January 2003, DOH issued a health advisory
FMRI Technical Report TR-9 11
Mercury Levels in Marine and Estuarine Fishes of Florida 1989–2001 Adams et al.
recommending limited consumption of common snook
from Florida Keys/Florida Bay (DOH, 2003).
Red grouper
Epinephelus morio
Red grouper, Epinephelus morio, principally inhabit
nearshore and offshore waters of Florida, although
juveniles are sometimes found in bays and inlets. Red
grouper are protogynous hermaphrodites; females
mature at age 4 to 6 and transition into males at age 7
to 14 (Moe, 1969). In the eastern Gulf of Mexico, spawn-
ing mostly occurs from March to June, with peak
spawning activity in April and May (Moe, 1969), but
spawning may occur from January to June (Johnson et
al., 1998). Red grouper feed on a variety of inverte-
brates and fish (Bullock and Smith, 1991).
This species is frequently landed in Florida’s
grouper-snapper fishery and is one of the most abun-
dant grouper species in commercial catches on Florida’s
gulf coast (Bullock and Smith, 1991; FWC-FMRI, 2001).
A total of 9,270,822 pounds of red grouper were land-
ed in Florida in 2000, of which approximately 99% were
landed from gulf coast waters (NMFS, Fisheries
Statistics and Economic Division, personal communi-
cation). More than 75% of all red grouper landed from
Florida gulf waters were caught in the commercial fish-
ery (FWC-FMRI, 2001).
Red grouper were principally collected from off-
shore waters of the Gulf of Mexico (n = 39), but samples
were also collected from the offshore waters adjacent
to the Florida Keys (n = 4), the Indian River Lagoon (n
= 3), and Volusia County (n = 3). Standard lengths (SL)
ranged from 338 to 565 mm. Total mercury levels for
individual fish ranged from 0.11 to 0.66 ppm.The mean
total mercury level in red grouper from the Gulf of Mex-
ico was 0.33 ppm, and the median was 0.32 ppm. Four
of the 39 Gulf of Mexico red grouper tested had mer-
cury levels greater than or equal to 0.5 ppm. Analysis
of red grouper from Gulf of Mexico waters revealed no
significant correlation between total mercury level and
fish length (P > 0.1); however, no large red grouper (>565
mm SL) were examined in this study. Samples from
larger specimens are required before the full range of
mercury levels in this species can be determined.
Gag
Mycteroperca microlepis
Gag, Mycteroperca microlepis, are found in estuarine,
nearshore, and offshore waters throughout Florida.
Estuaries are important nursery habitats for this species
(FWC-FMRI, 1991–2000; Grimes et al., 1995). Gag are
protogynous hermaphrodites; females mature between
the ages of 3 and 4 and can begin to transform into
males as early as age 5 (Collins et al., 1987; Hood and
Schlieder, 1992). Spawning occurs from approximate-
ly December to May (Hood and Schlieder, 1992). Gag
are a long-lived, slow-growing fish that can live for
more than 20 years (Collins, et al., 1987; Hood and
Schlieder, 1992). This species feeds primarily on fish-
es but also consumes a variety of invertebrates
(Naughton and Saloman, 1985).
This species is an important component of Flori-
da’s grouper-snapper fishery. A statewide total of
7,221,271 pounds of gag were landed by the commer-
cial and recreational fisheries in 2000, with
approximately 90% landed from gulf coastal waters
(FWC-FMRI, 2001).
Gag analyzed for mercury levels were principally
collected from the Tampa Bay area, Cedar Key, and
adjacent offshore waters of the Gulf of Mexico. Addi-
tional samples were collected from the Indian River
Lagoon and adjacent offshore waters (n = 12), Charlotte
Harbor (n = 3), Florida Keys/Florida Bay (n = 5), and
from the offshore waters of Volusia County (n = 7).
Mercury levels detected in sublegal-size gag (≤461
mm standard length [SL] on the gulf coast of Florida)
were usually low and were all less than or equal to 0.39
ppm. Mercury levels in legal-size individuals (≥461
mm SL on the gulf coast of Florida) were typically
higher; 43% of legal-size gag from Florida gulf coast
waters had mercury levels greater than or equal to 0.5
ppm. Dorsal muscle tissue samples from all 97 gag
(137–890 mm SL) had total mercury levels that ranged
from 0.04 to 1.80 ppm (Appendix Table). The mean
total mercury level for gag from the Tampa Bay area was
0.30 ppm, and the median was 0.21 ppm. Approxi-
12 FMRI Technical Report TR-9
Adams et al. Mercury Levels in Marine and Estuarine Fishes of Florida 1989–2001
mately 45% of gag collected from the Tampa Bay area
were of legal size, and 47% of these legal-size fish had
mercury levels greater than or equal to 0.5 ppm. The
mean total mercury level for gag from the Cedar Key
area was 0.47, and the median was 0.44 ppm. Ninety
percent of all gag collected from the Cedar Key area
were of legal size, and approximately 37% of these
legal-size fish had mercury levels greater than or equal
to 0.5 ppm.
Analysis of gag from the Tampa Bay area indicat-
ed there was a significant positive correlation between
total mercury level and fish length (P < 0.0001). There
was no significant relationship detected between total
mercury level and fish length from fish in the Cedar
Key area (P > 0.05); however, only gag within a relatively
limited size range (450–725 mm SL) were examined
from this location. The addition of larger and smaller
size-class gag from the Cedar Key area may potentially
alter these results. Because of the close proximity of
Ta mpa Bay to Cedar Key adjacent offshore waters, we
also analyzed gag pooled from these two areas (n = 70
fish) to examine the overall mercury-length relation-
ship from the central Florida gulf coast. There was a
significant positive correlation between total mercury
level and fish length (P < 0.0001) for fish from the cen-
tral Florida gulf coast region.
In January 2003, DOH issued a health advisory
recommending limited consumption of gag from Cedar
Key and Tampa Bay and adjacent waters (DOH, 2003).
Bluefish
Pomatomus saltatrix
Bluefish, Pomatomus saltatrix, are found in estuarine,
nearshore, and offshore waters throughout Florida.This
coastal pelagic, estuarine-dependent species spawns
in offshore waters of the Atlantic during spring and
summer (Chiarella and Conover, 1990; Juanes and
Conover, 1995). Limited spawning may occur off the
Florida and Georgia coasts during the fall (Kendall and
Walford, 1979; Collins and Stender, 1988). Based on the
occurrence of larvae, spawning in the northern Gulf of
Mexico occurs during April and October through
November (Ditty and Shaw, 1995). In the western North
Atlantic, bluefish spend their early juvenile stage in
nearshore or estuarine waters and return to continen-
tal shelf waters as large juveniles (Munch and Conover,
2000). Bluefish grow rapidly during their first year and
most individuals are mature by age 2 (Deuel, 1964; Wilk,
1977).The maximum estimated age for this species is 12
years (Chiarella and Conover, 1990), with a recorded
maximum total length of 1,100 mm and a recorded max-
imum weight of 12 kg (Robins and Ray, 1986).
Bluefish are one of the dominant marine pisci-
vores along the United States Atlantic coast (Juanes et
al., 1996). Both juveniles and adult bluefish consume
food at high rates and generally feed on fishes, although
invertebrates are also consumed (reviewed in Oliver
et al., 1989; Buckel et al., 1999a).The prey biomass con-
sumed annually by bluefish along the U.S. Atlantic
coast is estimated to be eight times the biomass of the
total bluefish population itself (Buckel et al., 1999b).
A total of 952,386 pounds of bluefish were landed
in Florida by the recreational and commercial fish-
eries during 2001, with the majority being landed on
the Atlantic coast (FWC-FMRI, Catch Rate Summary
1990-2002, FWC-FMRI Marine Fisheries Information
System). Approximately 92% of the total landings on
the Florida Atlantic coast during 2001 were from the
recreational fishery (deSilva, 2002).
Tw o hundred and twenty-six bluefish, ranging
from 103 mm to 783 mm SL, were collected from Flori-
da waters.The majority of fish were collected from the
Indian River Lagoon and adjacent offshore waters (n
= 149), with additional fish collected from Tampa Bay
(n = 27) and Charlotte Harbor (n = 25).The remaining
25 fish were collected from Florida Keys/Florida Bay,
Tequesta/southern Indian River Lagoon,Volusia Coun-
ty offshore waters, or northeast Florida.
Bluefish collected from the Indian River Lagoon
and adjacent offshore waters ranged from 239 mm to
731 mm SL, with a mean standard length of 346 mm.
Total mercury levels in bluefish from this area ranged
from 0.11 ppm to 1.50 ppm (mean = 0.44 ppm, medi-
an = 0.36 ppm). Total mercury levels in bluefish from
Ta mpa Bay ranged from 0.26 ppm to 1.60 ppm, (mean
= 0.87 ppm, median = 0.85 ppm) and in bluefish from
Charlotte Harbor ranged from 0.28 ppm to 2.00 ppm
(mean = 0.87 ppm, median = 0.68 ppm). Although sam-
ple sizes were unequal and the number of samples
from gulf coast waters were comparatively low, pre-
liminary analyses suggest that bluefish from Tampa Bay
and Charlotte Harbor contained significantly higher
total mercury levels than did those from the Indian
River Lagoon and adjacent offshore waters (Kruskal-
Wallis test, P < 0.001; Dunn’s method, P < 0.05).
Additional samples from Gulf of Mexico waters are
required to fully understand the regional differences
in total mercury content for this species. Analyses
indicated significant positive correlations between
FMRI Technical Report TR-9 13
Cobia
Rachycentron canadum
Mercury Levels in Marine and Estuarine Fishes of Florida 1989–2001 Adams et al.
Figure 4. Relationship between ln total mercury level (ppm) and
standard length (mm) of bluefish, Pomatomus saltatrix, from the
Indian River Lagoon and adjacent offshore waters, Florida. The
dashed line represents the anti-log equivalent of the 0.5-ppm
threshold level.
Figure 5. Relationship between ln total mercury level (ppm) and
standard length (mm) of bluefish, Pomatomus saltatrix, from
central Florida gulf coast waters.The dashed line represents the anti-
log equivalent of the 0.5-ppm threshold level.
total mercury level and fish length in the Indian River
Lagoon (P < 0.0001) (Figure 4), and in the central gulf
coast (Tampa Bay and Charlotte Harbor bluefish results
pooled) (P < 0.0001) (Figure 5).
Approximately 26% of all bluefish analyzed from
the Indian River Lagoon and adjacent offshore waters
contained total mercury levels greater than or equal to
0.5 ppm, and 1 individual contained a total mercury
level greater than or equal to 1.5 ppm. Ninety percent
of bluefish collected from the Indian River Lagoon
and adjacent offshore waters were of legal size (≥305
mm FL or 281 mm SL). A total of 29% of legal-size
bluefish from this area contained total mercury levels
greater than or equal to 0.5 ppm. Approximately 81%
of all bluefish analyzed from Tampa Bay contained
total mercury levels greater than or equal to 0.5 ppm,
and two of those individuals contained a total mercury
level greater than or equal to 1.5 ppm.With the excep-
tion of one fish, all bluefish sampled from Tampa Bay
were of legal size. Sixty-eight percent of all bluefish ana-
lyzed from Charlotte Harbor contained total mercury
levels greater than or equal to 0.5 ppm, and four of those
individuals contained a total mercury level greater
than or equal to 1.5 ppm. With the exception of one fish,
all bluefish sampled from Charlotte Harbor were of
legal size.
In January 2003, DOH issued a health advisory
recommending limited consumption of bluefish from
all coastal waters of Florida (DOH, 2003).
The coastal pelagic species cobia, Rachycentron canad-
um, is widely distributed along the Atlantic and gulf
coasts of Florida. These fish are migratory, typically
moving southward and/or offshore in response to
decreased water temperatures in the fall and winter
(Shaffer and Nakamura, 1989; Howse et al., 1992; Franks
et al., 1991). Females mature at approximately 2 years
of age (Lotz, et al., 1996). In the southeastern United
States, this species spawns from April to September
(Brown-Peterson et al., 2001). Maximum age observed
in the northeastern Gulf of Mexico was estimated to be
9 for males and 11 for females (Franks et al., 1999).
Maximum age observed in North Carolina coastal
waters was 14 for males and 13 for females (Smith,
1996). Cobia can grow to approximately 1,800 mm in
length and up to 68 kg in total weight (Robins and
Ray, 1986). Cobia feed on a wide variety of crustaceans,
fish, and squid. In the north-central Gulf of Mexico, por-
tunid crabs were the predominant food, with fish
14 FMRI Technical Report TR-9
Adams et al. Mercury Levels in Marine and Estuarine Fishes of Florida 1989–2001
becoming more important as the length of cobia
increased (Meyer and Franks, 1996).
Cobia is an important recreational species in the
waters of the southeastern United States but the com-
mercial fishery in Florida also lands these fish, typically
as incidental catch. A total of 1,302,300 pounds of cobia
were landed in Florida during 2000; approximately
88% of those were landed by the recreational fishery
(FWC-FMRI, 2001; NMFS, Fisheries Statistics and Eco-
nomic Division, personal communication).
Cobia were principally collected from offshore
waters adjacent to the Indian River Lagoon (n = 20) and
in Tampa Bay and adjacent offshore waters (n = 11), with
the remainder of fish (n = 12) being collected through-
out Florida coastal waters. Standard lengths of fish
sampled ranged from 362 to 1342 mm. Mercury levels
detected in the 43 cobia analyzed during this study
ranged from 0.13 to 2.00 ppm. The mean total mer-
cury level for cobia from offshore waters adjacent to the
Indian River Lagoon was 0.57 ppm (median = 0.40
ppm). Analysis of cobia from offshore waters adjacent
to the Indian River Lagoon revealed a positive corre-
lation between total mercury level and fish length (P
< 0.001). Approximately 39% of cobia analyzed from
Florida waters contained mercury levels greater than
or equal to 0.5 ppm. Approximately 14% of all cobia
analyzed from Florida waters contained mercury lev-
els greater than or equal to 1.5 ppm. All cobia
containing mercury levels greater than or equal to 1.5
ppm were greater than 800 mm SL.
In January 2003, DOH issued a health advisory
based on additional results recommending limited
consumption of cobia from all coastal waters of Flori-
da (DOH, 2003).
Crevalle jack
Caranx hippos
The crevalle jack, Caranx hippos, inhabits Florida’s off-
shore, nearshore, and estuarine waters. The life history
of this species is not well known. Crevalle jack proba-
bly spawn from April to June (Snelson, 1992) and can
attain a total length of approximately 1,500 mm (Robins
and Ray, 1986) and a total weight of approximately 23
kg (FWC-FMRI, unpublished data). Crevalle jack have
been found to feed on a variety of fish and small inver-
tebrates (Reid, 1954; Darnell, 1958), but data on the
feeding habits of this species are limited.
Crevalle jack support both commercial and recre-
ational fisheries in Florida waters. A total of 2,293,200
pounds of crevalle jack were landed in Florida during
2000; approximately 69% of those were landed by recre-
ational fishermen (FWC-FMRI, 2001; NMFS, Fisheries
Statistics and Economic Division, personal communi-
cation). Fifty-one percent of crevalle jack landings were
made on the gulf coast during the 1995–2000 time peri-
od (Murphy et al., 2001).
Mercury levels detected in crevalle jack were mod-
erately high in several of Florida’s estuarine systems.
Crevalle jack were collected in Tampa Bay, the Indian
River Lagoon, Charlotte Harbor, Cedar Key, and Flori-
da Keys/Florida Bay. The 169 crevalle jack (152–575
mm standard length) analyzed contained total mercury
levels ranging from 0.02 to 3.90 ppm. Mean total mer-
cury levels were comparable for fish from Tampa Bay
(mean = 0.61 ppm; median = 0.57 ppm), the Indian
River Lagoon (mean = 0.53 ppm; median = 0.54 ppm),
and Charlotte Harbor (mean = 0.51 ppm; median = 0.44
ppm); however, levels in crevalle jack from Florida
Keys/Florida Bay (mean = 0.97 ppm; median = 0.76
ppm) were noticeably higher (Appendix Table). Mean
total mercury levels of fish from the Cedar Key area
were lower (mean = 0.28 ppm; median = 0.30 ppm) than
in fish from other study areas, but this was likely influ-
enced by the relatively small size of the fish collected
in this area (mean = 258 mm SL).
There were no significant correlations detected
between total mercury level and fish length for crevalle
jack from the Indian River Lagoon (P > 0.01) or from
Tampa Bay (P > 0.1). Analysis of crevalle jack from
Florida Keys/Florida Bay revealed a significant posi-
tive correlation between total mercury level and fish
length (P < 0.001). Overall, mean total mercury levels
in crevalle jack tested from Florida waters were often
greater than or equal to 0.5 ppm. Approximately 54%
of all crevalle jack examined in Florida had mercury
levels greater than or equal to 0.5 ppm. In the Florida
Keys, where the highest mercury burdens were detect-
ed, 65% of all crevalle jack had levels greater than or
equal to 0.5 ppm.
After reviewing these results, the Florida Depart-
ment of Health (HRS, 1995) released a health advisory
on 6 October 1995 urging limited consumption of
crevalle jack from specific Florida waters. In January
2003, DOH issued a health advisory recommending
limited consumption of crevalle jack from all coastal
waters of Florida (DOH, 2003).
FMRI Technical Report TR-9 15
Mercury Levels in Marine and Estuarine Fishes of Florida 1989–2001 Adams et al.
Greater amberjack
Seriola dumerili
The greater amberjack, Seriola dumerili, is a pelagic
and epibenthic species that is widely distributed along
the Atlantic and gulf coasts of Florida. These fish are
often associated with reef habitats, rock piles or ledges,
and wrecks in offshore waters. This species spawns
during the spring and summer, and the majority of indi-
viduals are mature by 3 to 4 years of age (Thompson
et al., 1992; reviewed in Cummings and McClellan,
2000). Maximum age observed was estimated to be 17
years (Manooch and Potts, 1997a), and all fish over 9
years of age, at least in the northern Gulf of Mexico,
were female (Thompson et al., 1999). Greater amber-
jack is one of the largest species in the family
Carangidae and can grow to over 2,000 mm in length
and up to 86 kg in total weight (Manooch and Potts,
1997b).
Greater amberjack are commercially important,
as a bycatch of reef fish fisheries as well as a targeted
commercial species, and also support a large recre-
ational fishery in the waters of the southeastern United
States (McClellan and Cummings, 1997). During the
late 1970s, catches and utilization of greater amberjack
increased as the species gained popularity as a game-
fish and the demand for smoked amberjack meat grew
(Cummings and McClellan, 1999). In the recent past,
human consumption and overall marketability of this
species has varied because of consumer concerns about
parasite infestations within the muscle tissue (Berry and
Burch, 1979; Manooch and Potts, 1997b) and ciguatera
poisoning (Manooch and Potts, 1997b). The current
recreational size limit in Florida waters is 28 inches fork
length (approximately 711 mm FL), with a bag limit of
one fish per person per day. Despite size limits, bag lim-
its, and seasonal closures implemented in the early
1980s, landings in Florida waters have continued to be
substantial. A total of 2,769,505 pounds of greater
amberjack were landed in Florida during 2000, with 54%
of the statewide total being landed by the recreation-
al fishery (Murphy et al., 2001). Between 50% and 70%
of Florida landings since 1994 have been from the gulf
coast (Murphy et al., 2001). Migrational patterns deter-
mined from tag-recapture results (McClellan and
Cummings, 1997) and genetic analyses indicate that in
the southeastern United States greater amberjack form
two subpopulations or stocks: one along the Atlantic
coast, including the Florida Keys, and one in the north-
ern Gulf of Mexico (Gold and Richardson, 1998).
A total of 67 greater amberjack were collected in
Florida for mercury analysis, with the majority (approx-
imately 61%) being from offshore waters near Volusia
County on the Atlantic coast. Standard lengths of fish
sampled ranged from 535 to 1,069 mm, and the mean
size for all Florida fish was 806 mm. Mercury levels
detected in individuals from Volusia County offshore
waters ranged from 0.20 to 1.00 ppm and the mean total
mercury level from this area was 0.46 ppm with a
median of 0.38 ppm. Approximately 40% of greater
amberjack tested from Florida waters had total mer-
cury levels greater than or equal to 0.5 ppm. No greater
amberjack contained total mercury levels greater than
or equal to 1.5 ppm. A total of 88% of greater amber-
jack collected from Florida waters were of legal size
(≥711 mm FL or 647 mm SL). Approximately 42% of all
legal-size greater amberjack analyzed in this study
contained total mercury levels greater than or equal to
0.5 ppm. Analysis of greater amberjack from Volusia
County offshore waters revealed a significant positive
correlation between total mercury level and fish length
(P < 0.0001).
In January 2003, DOH issued a health advisory
recommending limited consumption of greater amber-
jack from all coastal waters of Florida (DOH, 2003).
Florida pompano
Trachinotus carolinus
Florida pompano, Trachinotus carolinus, are found in
Florida’s nearshore and estuarine waters. Juvenile Flori-
da pompano inhabit high-energy surf-zone areas but
also occur within estuarine waters near oceanic inlets.
Adult Florida pompano occur along coastal beaches and
within estuaries (Berry and Smith-Vaniz, 1978; FWC-
FMRI, 1991–2000), but adults also occur in offshore
waters (Cody et al., 2000). Spawning is thought to occur
16 FMRI Technical Report TR-9
The greater amberjack, Seriola dumerili, is a pelagic
and epibenthic species that is widely distributed along
the Atlantic and gulf coasts of Florida. These fish are
often associated with reef habitats, rock piles or ledges,
and wrecks in offshore waters. This species spawns
during the spring and summer, and the majority of indi-
viduals are mature by 3 to 4 years of age (Thompson
et al., 1992; reviewed in Cummings and McClellan,
2000). Maximum age observed was estimated to be 17
years (Manooch and Potts, 1997a), and all fish over 9
years of age, at least in the northern Gulf of Mexico,
were female (Thompson et al., 1999). Greater amber-
jack is one of the largest species in the family
Carangidae and can grow to over 2,000 mm in length
and up to 86 kg in total weight (Manooch and Potts,
1997b).
Greater amberjack are commercially important,
as a bycatch of reef fish fisheries as well as a targeted
commercial species, and also support a large recre-
ational fishery in the waters of the southeastern United
States (McClellan and Cummings, 1997). During the
late 1970s, catches and utilization of greater amberjack
increased as the species gained popularity as a game-
fish and the demand for smoked amberjack meat grew
(Cummings and McClellan, 1999). In the recent past,
human consumption and overall marketability of this
species has varied because of consumer concerns about
parasite infestations within the muscle tissue (Berry and
Burch, 1979; Manooch and Potts, 1997b) and ciguatera
poisoning (Manooch and Potts, 1997b). The current
recreational size limit in Florida waters is 28 inches fork
length (approximately 711 mm FL), with a bag limit of
one fish per person per day. Despite size limits, bag lim-
its, and seasonal closures implemented in the early
1980s, landings in Florida waters have continued to be
substantial. A total of 2,769,505 pounds of greater
amberjack were landed in Florida during 2000, with 54%
of the statewide total being landed by the recreation-
al fishery (Murphy et al., 2001). Between 50% and 70%
of Florida landings since 1994 have been from the gulf
coast (Murphy et al., 2001). Migrational patterns deter-
mined from tag-recapture results (McClellan and
Adams et al. Mercury Levels in Marine and Estuarine Fishes of Florida 1989–2001
from spring to early fall, likely in offshore waters (Fields,
1962; Finucane, 1969). Florida pompano grow rapidly
and can attain a length of approximately 255 mm SL
after one year (FWC-FMRI, unpublished data). Most
female Florida pompano mature between ages 2 and
3, with males likely maturing during their first year
(FWC-FMRI, unpublished data).This species feeds on
a wide variety of invertebrates, including amphipods,
copepods, shrimps, gastropods, bivalves, and crabs, as
well as small fishes (Finucane, 1969; Bellinger and
Avault, 1971; Armitage and Alevizon, 1980).
Florida pompano are considered among the finest
food-fish species and can yield one of the highest per
pound prices of any marine food fish in the United
States (Gilbert, 1986a).This species supports important
recreational and commercial fisheries in Florida waters.
Florida’s overall landings totaled 1,160,463 pounds in
2000, with over 58% of total landings made by the
recreational fishery (Murphy et al., 2001). Approxi-
mately two-thirds of Florida’s recreational fishery
harvest of Florida pompano is made on the Atlantic
coast (Murphy et al., 1996).
Florida pompano were collected from the Indian
River Lagoon and adjacent coastal waters (n = 51),
Charlotte Harbor (n = 13), Tampa Bay (n = 10), and
Florida Keys/Florida Bay (n = 4). Standard lengths of
fish sampled ranged from 61 to 412 mm. Mercury lev-
els detected in Florida pompano were typically low.
Total mercury levels in individual fish ranged from
0.03 to 0.49 ppm.The mean total mercury levels ranged
from 0.10 ppm (median = 0.10 ppm) in the Indian River
Lagoon and adjacent coastal waters to 0.23 ppm (medi-
an = 0.21 ppm) in Tampa Bay. Analysis of Florida
pompano from the Indian River Lagoon area revealed
a weak positive correlation between total mercury
level and fish length (P < 0.01). No Florida pompano col-
lected from Florida waters contained mercury levels
greater than or equal to 0.5 ppm.
Permit
Trachinotus falcatus
Permit, Trachinotus falcatus, are found in Florida’s estu-
arine and nearshore waters along the central and south-
ern Atlantic coast and the gulf coast. Juvenile permit
inhabit high-energy estuarine shorelines, typically over
sand-shell bottom (FWC-FMRI, 1991–2000), and along
exposed sandy beaches of the gulf and Atlantic coasts
of Florida. Adult permit occur near reefs, sand flats,
and channels (Berry and Smith-Vaniz, 1978; FWC-FMRI,
unpublished data).The biology and life history of per-
mit are not well known. Permit spawn during the late
spring and early summer (Armstrong et al., 1996). Age
and size at maturity of permit are not known, but pre-
liminary data from Tampa Bay suggest that maturity does
not occur until permit reach approximately 400 mm SL
(FWC-FMRI, unpublished data). Permit can attain large
sizes and have been reported to grow to 1,140 mm total
length and 23 kg total weight (Robins and Ray, 1986). No
other data regarding age and growth of this species are
currently available.This species feeds on a wide variety
of invertebrates, including amphipods, shrimps, gas-
tropods, bivalves, and crabs (Randall, 1967; Finucane,
1969; Carr and Adams, 1973).
This species is landed recreationally and com-
mercially, but data concerning the recreational harvest
are limited. Florida’s overall landings totaled 149,919
pounds in 2000 (Murphy et al., 2001). More than 80%
of the total commercial harvest of permit in Florida dur-
ing 1981–1995 was landed on the gulf coast (Armstrong
et al., 1996).
Permit were principally collected from the Florida
Keys/Florida Bay (n = 105) and Tampa Bay (n = 34), but
a small number of samples were also collected from the
Indian River Lagoon system (n = 18) and Charlotte
Harbor (n = 6). Standard lengths of fish sampled ranged
from 55 to 887 mm. Mercury levels detected in permit
were usually low, and fish with relatively high levels
were usually larger than the upper “slot limit”length
for this species (462 mm SL). Total mercury levels for
individual fish ranged from 0.02 to 2.30 ppm. Mean total
mercury levels were low for fish in Tampa Bay (mean
= 0.15 ppm; median = 0.11 ppm) and in the Indian
River Lagoon (mean = 0.22 ppm; median = 0.08 ppm),
but were noticeably higher in the Florida Keys/Flori-
da Bay (mean = 0.61 ppm; median = 0.46 ppm).
Analysis of permit from the Florida Keys/Florida
Bay area indicated a significant positive correlation
between total mercury level and fish length (P < 0.0001).
Analysis of permit from Tampa Bay revealed no sig-
nificant correlation between total mercury level and fish
length (P > 0.1); however, only fish from a limited size
range (155–360 mm SL) were sampled from this area.
Only one permit from Tampa Bay had mercury levels
greater than or equal to 0.5 ppm. Approximately 46%
of permit examined from the Florida Keys/Florida Bay
area had mercury levels greater than or equal to 0.5
FMRI Technical Report TR-9 17
Mercury Levels in Marine and Estuarine Fishes of Florida 1989–2001 Adams et al.
Figure 6. Relationship between ln total mercury level (ppm) and
standard length (mm) of dolphin, Coryphaena hippurus, from
central Florida Atlantic offshore waters.The dashed line represents
the antilog equivalent of 0.5-ppm threshold level.
ppm. Most of the permit with higher mercury levels
(≥0.5 ppm) were larger, presumably adult individuals
(>600 mm SL). Approximately 3% of permit examined
from the Florida Keys/Florida Bay area had mercury
levels greater than or equal to 1.5 ppm.
In January 2003, DOH issued a health advisory
recommending limited consumption of permit from
Florida Keys/Florida Bay (DOH, 2003).
Dolphin
Coryphaena hippurus
Dolphin, Coryphaena hippurus, is an offshore pelagic
species found along both coasts of Florida and cir-
cumglobally in subtropical and tropical waters. In
Florida, the majority of spawning occurs from Decem-
ber to May (Beardsley, 1967; FWC-FMRI, unpublished
data). Dolphin first reach sexual maturity at approxi-
mately 450–500 mm FL (or approximately 418–465 mm
SL) during their first year of growth (FWC-FMRI,
unpublished data). Dolphin grow rapidly and can
reach a length of 1,100 mm FL (approximately 1023
mm SL) during their first year (Massuti et al., 1999). Cur-
rent genetic information suggests that dolphin from the
Atlantic, U.S. Caribbean, and Gulf of Mexico form one
stock (SAFMC, 2000). Dolphin eat a wide variety of
offshore fishes (e.g., flying fish, halfbeaks, filefish, trig-
gerfish, sargassumfish, tunas, jacks) and invertebrates
(e.g., squids, shrimps) and are also known to be can-
nibalistic (reviewed in Palko et al., 1982; Manooch et al.,
1984; reviewed in SAFMC, 2000).
This species, often called mahi-mahi or dorado,
supports significant recreational and commercial fish-
eries in Florida. A total of 9,344,560 pounds of dolphin
were landed in Florida during 2000, with the majority
(approximately 71%) being landed along the Atlantic
coast (Murphy et al., 2001).The vast majority (approx-
imately 92%) of total landings in Florida are from the
recreational fishery (Murphy et al., 2001), similar to
the proportion of total landings for recreational fish-
eries in other parts of the South Atlantic region
(SAFMC, 2000). In the U.S. western North Atlantic,
the largest percentage of dolphin landings have been
reported from the Atlantic coast of Florida to North Car-
olina (Thompson, 1999).
A total of 205 dolphin, ranging from 410 mm to 1,305
mm SL, were collected from Florida waters for mercury
analysis. The greatest number (n = 130) were collect-
ed from offshore waters adjacent to the Indian River
Lagoon system along Florida’s central Atlantic coast.
Mercury levels for dolphin in Florida were low in all
regions.The mean total mercury level for fish collect-
ed along Florida’s central Atlantic coast was 0.11 ppm
(median = 0.07 ppm). Analysis of dolphin from Flori-
da’s central Atlantic coast offshore waters revealed a
significant positive correlation between total mercury
level and fish length (P < 0.0001)(Figure 6).
Only one dolphin tested from Florida waters con-
tained a total mercury level equal to 0.5 ppm. This
1,243 mm SL male (approximately 4 years old), the
largest individual collected from offshore waters adja-
cent to the Indian River Lagoon system, contained
0.5-ppm total mercury.
Gray snapper
Lutjanus griseus
18 FMRI Technical Report TR-9
Adams et al. Mercury Levels in Marine and Estuarine Fishes of Florida 1989–2001
The gray, or mangrove, snapper, Lutjanus griseus, inhab-
its central and south Florida’s reef and near-reef areas
but also resides in estuarine habitats as adults and
juveniles (Stark, 1971; Bortone and Williams, 1986;
FWC-FMRI, 1991–2000). Spawning occurs in offshore
waters from June to September (Stark, 1971). Both sexes
of gray snapper attain sexual maturity at approximately
190 mm SL (Koenig, 1993).This species can live 25 years
and grow to 764 mm total length (Johnson et al., 1994).
Gray snapper in north Florida waters tend to be larg-
er and older than those caught in the fishery in south
Florida (Manooch and Matheson, 1981; Johnson et al.,
1994). Along the Atlantic coast of Florida (using Sebas-
tian Inlet [27.8°N latitude] as the north-south dividing
line), gray snapper from the north tend to grow to a larg-
er size and live longer than those from the south (Burton,
2001).These latitudinal age and growth differences are
likely related to greater fishing pressure on gray snap-
per in south Florida (Manooch and Matheson, 1981).
Gray snapper are opportunistic predators that feed on
a variety of fish and crustaceans, but data on the feed-
ing habits of this species are limited (Stark, 1971; Bortone
and Williams, 1986).
Gray snapper support major commercial and recre-
ational fisheries in Florida waters. A total of 1,911,450
pounds of gray snapper were landed in Florida during
2000; of those, approximately 64% were landed on the
gulf coast (Murphy et al., 2001). Overall landings have
been relatively steady since 1982 on the Atlantic coast
and since 1985 on the gulf coast, although there has
been a slow decline on the gulf coast since 1995 (Mur-
phy et al., 2000).
Gray snapper were collected in Tampa Bay and
adjacent offshore waters, the Indian River Lagoon,
Charlotte Harbor, and Florida Keys/Florida Bay. A lim-
ited number of samples were also collected from Volusia
County waters (n = 15) and Tequesta/southern Indian
River Lagoon (n = 2). The 301 gray snapper analyzed
for levels of total mercury ranged from 104 to 505 mm
standard length (SL). The majority (77%) of fish col-
lected from all areas were less than 300 mm SL.
Mercury levels detected in gray snapper from Florida
waters were usually low.Total mercury levels for indi-
vidual fish ranged from 0.03 to 0.65 ppm. Mean total
mercury levels were low in all study areas: Tampa Bay
(mean = 0.23 ppm; median = 0.19 ppm), Indian River
Lagoon (mean = 0.19 ppm; median = 0.17 ppm), Char-
lotte Harbor (mean = 0.13 ppm; median = 0.13 ppm),
and Florida Keys/Florida Bay (mean = 0.21 ppm; medi-
an = 0.19 ppm) (Appendix Table).
Analyses indicated a positive correlation between
total mercury level and fish length (P < 0.0001) of gray
snapper from the Indian River Lagoon, Charlotte Har-
bor, and Florida Keys/Florida Bay; however, no large
fish (>300 mm SL) were sampled from these areas.
There were no significant correlations detected between
total mercury level and fish length (P > 0.01) of fish from
Ta mpa Bay. Approximately 84% of gray snapper col-
lected from Florida waters were of legal size (≥254 mm
TL or 202 mm SL), and of these individuals, approxi-
mately 3% contained total mercury levels greater than
or equal to 0.5 ppm (n = 8). Overall, only nine gray snap-
per tested from Florida waters had total mercury levels
greater than or equal to 0.5 ppm. Six of these nine fish
with levels greater than 0.5 ppm were from the Flori-
da Keys/Florida Bay area.
Tripletail
Lobotes surinamensis
Tripletail, Lobotes surinamensis, is a pelagic species
found throughout Florida’s Atlantic and gulf coasts
and globally in tropical and subtropical waters. This
species is frequently observed near the surface near
floating structure (e.g., sargassum weed, flotsam) as well
as in association with buoys, pilings, reefs, and relat-
ed habitats. Along the U.S. Atlantic coast and in the Gulf
of Mexico, this species spawns in offshore waters dur-
ing spring and summer months (Merriner and Foster,
1974; Ditty and Shaw, 1994; FWC-FMRI, unpublished
data).Tripletail grow rapidly during the first few years
of life, and preliminary data indicate that this species
may reach sexual maturity at age 1 (Armstrong et al.,
1996). Based on preliminary estimates, maximum ages
for this species are age 6 for males and age 7 for females
(FWC-FMRI, unpublished data).
More than 90% of tripletail landings in Florida are
from the Atlantic coast. A total of 558,916 pounds of
tripletail were landed in Florida during 2000 (FWC-
FMRI, 2001).
A total of 114 tripletail, ranging from 270 mm to 620
mm SL, were collected from Florida waters for mercury
analysis. Most of these individuals (n = 104) were of
legal size (≥381 mm TL or approximately 318 mm SL).
The majority were collected from the Indian River
Lagoon and adjacent offshore waters (n = 74; mean =
FMRI Technical Report TR-9 19
n
e
<
.
-
n
r
a
a
Mercury Levels in Marine and Estuarine Fishes of Florida 1989–2001 Adams et al.
430 mm SL) and from Florida Keys/Florida Bay (n = 39;
mean = 378 mm SL). Total mercury levels in tripletail
from the Indian River Lagoon and adjacent offshore
waters were typically low, ranging from 0.01 ppm to 0.61
ppm (mean = 0.13 ppm; median = 0.11). Although
tripletail from Florida Keys/Florida Bay were signifi-
cantly smaller in length than those collected from the
Indian River Lagoon and adjacent offshore waters (t-
test, P< 0.001), total mercury levels in fish from Florida
Keys/Florida Bay (mean = 0.27 ppm, median = 0.19
ppm) were significantly higher (Mann-Whitney rank
sum test, P< 0.001) than those in fish from the Indian
River Lagoon and adjacent offshore waters.
Analysis indicated a significant correlation betwee
total mercury level and fish length for tripletail from th
Indian River Lagoon and adjacent offshore waters (P
0.0001) and from Florida Keys/Florida Bay (P< 0.0001)
Approximately 5% of all tripletail examined from Flori
da waters contained total mercury levels greater tha
or equal to 0.5 ppm. Of the six tripletail greater than o
equal to 0.5 ppm, five were from Florida Keys/Florid
Bay. No tripletail examined from Florida waters had
mercury level greater than 0.8 ppm.
White Grunt
Haemulon plumieri
The white grunt,Haemulon plumieri, is a coastal species
found throughout Florida. Along the U.S.Atlantic coast
and in the Gulf of Mexico, this species spawns from
spring to early fall, with peak spawning during April,
May, and June (Padgett, 1997; Murie and Parkyn, 1999).
Female and male white grunts first reach sexual matu-
rity between 180 and 210 mm TL (approximately 143-167
mm SL). All individuals are mature when greater than
250 mm TL (approximately 198 mm SL) and are approx-
imately 2 to 3 years old (Murie and Parkyn, 1999).The
maximum age determined for this species is 27 years
in the South Atlantic Bight (Padgett, 1997) and 14 years
on the gulf coast of Florida (Murie and Parkyn, 1999).
White grunt are known to feed upon worms, gas-
tropods, and crustaceans (Böhlke and Chapman, 1968).
This species is commonly landed in Florida recre-
ational and commercial fisheries.The majority of white
grunt landings in both fisheries are from the Gulf of
Mexico (Murphy et al., 1999). Landings of white grunt
in Florida are typically reported as an aggregate with
other grunt species (e.g., pigfish, Orthopristis chrysoptera;
tomtate, H. aurolineatum; margate, H. album).Total Flori-
da landings of grunts (all species combined) in 2000
were 2,825,451 pounds, with the majority (87%) being
landed on the gulf coast (FWC-FMRI, 2001).
A total of 63 white grunts, ranging from 100 mm to
360 mm SL, were collected from Florida waters for
mercury analysis. The greatest number (n = 32) were
collected from Gulf of Mexico waters offshore from the
Tampa Bay area. The mean standard length for fish
collected in Gulf of Mexico waters off Tampa Bay was
240 mm.The mean total mercury level for fish collect-
ed Gulf of Mexico waters off Tampa Bay was 0.32 ppm
(median = 0.31 ppm).Total mercury levels in all areas
of Florida ranged from 0.07 ppm to 0.61 ppm. Approx-
imately 11% of white grunts tested from Florida waters
contained a total mercury level equal to 0.5 ppm. Analy-
sis of white grunt from Tampa Bay indicated a weak
positive correlation between total mercury level and
fish length (P< 0.01). Additional samples from through-
out Florida are required to fully assess mercury levels
in this species.
Pigfish
Orthopristis chrysoptera
Pigfish, Orthopristis chrysoptera, are found in estuarine,
nearshore, and offshore waters along Florida’s Atlantic
and gulf coasts. Adult and juvenile pigfish inhabit a wide
range of estuarine habitats, such as seagrass flats,
sponge reefs, and channels or basins (Darcy, 1983;
Mitchell and Adams, 1993). Adult pigfish also occur in
nearshore and offshore areas, including reefs, jetties,
offshore platforms, and open-shelf habitats (Darcy,
1983).The biology of pigfish is not well known. Pigfish
spawn during the spring in Florida (Springer and Wood-
burn, 1960, Reid,1954), mature during the second year
(Taylor, 1916; Hildebrand and Cable, 1930), can live for
at least four years (Taylor,1916; Hildebrand and Cable,
1930), and can reach a maximum size of 460 mm stan-
dard length (SL) and 0.9 kg (Courtenay and Sahlman,
20 FMRI Technical Report TR-9
Adams et al. Mercury Levels in Marine and Estuarine Fishes of Florida 1989–2001
1978).This species feeds primarily on benthic inverte-
brates such as amphipods and shrimps (Reid, 1954;
Darcy, 1983; Carr and Adams, 1973).
This species is landed recreationally and com-
mercially and is considered to be a good-quality food
fish (Darcy, 1983).There is no season, size, or bag limit
for this species. Pigfish are also used extensively as live
bait by recreational and commercial fishermen. In the
Indian River Lagoon system, the commercial hook-
and-line fishery for spotted seatrout, Cynoscion
nebulosus, is dependent upon recruitment of pigfish,
which are used as bait. Pigfish landings are typically
pooled with other grunt species (e.g., white grunt,
Haemulon plumieri, and tomtate, H. aurolineatum) (Mur-
phy and Muller, 1995).Total Florida landings of grunts
(all species combined) in 2000 were 2,825,451 pounds,
with the majority (87%) being landed on the gulf coast
(FWC-FMRI, 2001).
Pigfish were collected from the Indian River
Lagoon (n = 21), Charlotte Harbor (n = 11), Florida
Keys/Florida Bay (n = 11), Tampa Bay (n = 7),
Choctawhatchee Bay (n = 1), and Volusia County waters
(n = 1); sampled pigfish ranged from 107 to 260 mm SL.
Mercury levels detected in pigfish were usually low.
Total mercury levels in individual fish ranged from
0.02 to 0.66 ppm (Appendix Table). The mean total mer-
cury level for pigfish in the Indian River Lagoon was
0.14 ppm (median = 0.12 ppm).The mean total mercury
level for this species in Charlotte Harbor was 0.20 ppm
(median = 0.13 ppm).The mean total mercury level for
pigfish from Florida Keys/Florida Bay was 0.12 ppm,
and the median was 0.12 ppm. Analysis of pigfish from
the Indian River Lagoon revealed a weak positive cor-
relation between total mercury level and fish length (P
< 0.01). Florida-wide, only one pigfish (collected in
Charlotte Harbor) tested had a mercury level greater
than or equal to 0.5 ppm.
Sheepshead
Archosargus probatocephalus
Sheepshead, Archosargus probatocephalus, inhabit a
wide array of estuarine, nearshore, and offshore habi-
tats along the gulf and Atlantic coasts of Florida. Spawn-
ing occurs from February through April (Tucker and
Barbera, 1987; Render and Wilson, 1992). Sheepshead
grow rapidly to an age of 6–8 years (Beckman et al.,
1991), and most are mature by age 2 (Render and Wil-
son, 1992). Maximum age is at least 20 years old
(Beckman et al., 1991). Sheepshead feed on algae and
various invertebrates (Ogburn, 1984).
Sheepshead are landed recreationally and com-
mercially in Florida waters.Total Florida landings were
2,874,370 pounds in 2000; of these, approximately 86%
were derived from the recreational fishery (Murphy et
al., 2001).
Sheepshead were collected in Cedar Key (n = 62),
Apalachicola Bay (n = 28), Tampa Bay (n = 27), Florida
Keys/Florida Bay (n = 25), Charlotte Harbor (n = 17),
Indian River Lagoon (n = 14), and Choctawhatchee
Bay (n = 4).The 177 sheepshead analyzed for levels of
total mercury ranged from 133 to 470 mm Standard
Length. Mercury levels detected in sheepshead from
Florida waters were usually low. Total mercury levels
for individual fish ranged from 0.06 to 1.10 ppm
(Appendix Table). Mean total mercury levels were low
in all areas. The highest mean level was 0.24 ppm
(median = 0.21), in sheepshead collected in Cedar Key.
Mean total mercury levels in fish from all other areas
were similar and ranged from 0.15 to 0.21 ppm. Over-
all, 2.8% of sheepshead (n = 5) tested from Florida
waters had a level greater than or equal to 0.5 ppm.The
majority (82%) of all sheepshead examined in this
study were of legal size (≥305 mm TL or approximate-
ly 242 mm SL). Only 2.7% of legal-size sheepshead
from Florida waters had a level greater than or equal
to 0.5 ppm. Analysis of sheepshead in Tampa Bay (P >
0.05) and Apalachicola Bay (P > 0.1) indicated there was
no significant correlation between total mercury level
and fish length; however, significant correlations were
detected for sheepshead in Cedar Key (P < 0.0001) and
Florida Keys/Florida Bay (P < 0.0001).
Sand seatrout
Cynoscion arenarius
The sand seatrout, Cynoscion arenarius, is reportedly
endemic to the Gulf of Mexico and occurs from south-
west Florida to the Bay of Campeche, Mexico (Roessler,
FMRI Technical Report TR-9 21
Mercury Levels in Marine and Estuarine Fishes of Florida 1989–2001 Adams et al.
1970; Hildebrand, 1955); it is one of the most abundant
species in estuarine and nearshore waters of the gulf
coast (Christmas and Waller, 1973). Preliminary results
from ongoing research at FMRI suggest that this species
also occurs on the Atlantic coast of Florida (FWC-
FMRI, unpublished data).
Sand seatrout inhabit numerous types of habitat
within estuarine and nearshore waters of the gulf.This
species spawns during spring and late summer (Mof-
fett et al., 1979), matures during the first year at between
140 and 180 mm TL (approximately 106–143 mm SL)
(Shlossman and Chittenden, 1981), and can attain total
lengths of up to 590 mm (approximately 523 mm SL)
(Trent and Pristas, 1977). Few sand seatrout appear to
grow larger than 300 mm TL (approximately 254 mm
SL) (Shlossman and Chittenden, 1981).
Juvenile sand seatrout feed on mysids, penaeoid
shrimp, and copepods; adults feed mostly on small
fishes (e.g., bay anchovies, Anchoa mitchilli; gulf men-
haden, Brevoortia patronus) (Reid et al., 1956; Darnell,
1958; Moffett et al., 1979; Sheridan, 1979; Overstreet
and Heard, 1982).The diet of the sand seatrout is influ-
enced by location and habitat type (Sheridan, 1979).
In 2000, 5,312 pounds of sand seatrout were com-
mercially landed from Florida gulf coast waters
(FWC-FMRI, 2001). An estimated 1,587,181 fish were
landed recreationally in Florida during 2000 (FWC-
FMRI, 2001).
A total of 104 sand seatrout were collected from
areas throughout Tampa Bay, Cedar Key, and Charlotte
Harbor for mercury analysis.The majority of samples
were collected from the Hillsborough Bay and Safety
Harbor regions of the Tampa Bay system. Standard
lengths of sampled fish ranged from 145 to 337 mm.
Mercury levels detected in sand seatrout from Flori-
da waters were variable. Total mercury levels for
individual fish ranged from 0.11 to 1.20 ppm. Mean total
mercury levels were 0.46 ppm (median = 0.44 ppm) in
Tampa Bay, 0.81 ppm (median = 0.80 ppm) in Charlotte
Harbor, and 0.34 ppm (median = 0.32 ppm) in Cedar
Key (Appendix Table). The mean total length of sand
seatrout analyzed from Charlotte Harbor (283 mm SL)
was larger than that of fish from Tampa Bay (224 mm
SL) and Cedar Key (266 mm SL). Overall, sand seatrout
collected in Charlotte Harbor were significantly larg-
er than those sampled in Tampa Bay (Kruskal-Wallis
test, P < 0.0001; Dunn’s method, P < 0.05), and the high-
er mean total mercury level observed in Charlotte
Harbor may be due, in part, to these size differences.
Analysis of sand seatrout from Tampa Bay indicated
a weak positive correlation between total mercury
level and fish length (P < 0.01), but further analyses of
fish collected only from the Hillsborough Bay area of
Ta mpa Bay (n = 30 fish) revealed a stronger relation-
ship (P < 0.001). Approximately 62% of all sand seatrout
analyzed from Florida waters contained levels greater
than or equal to 0.5 ppm. No sand seatrout analyzed
from Florida waters contained levels greater than or
equal to 1.5 ppm.
Spotted seatrout
Cynoscion nebulosus
The spotted seatrout, Cynoscion nebulosus, occurs in
estuarine and nearshore waters of the gulf and Atlantic
coasts of Florida. Juvenile spotted seatrout frequently
inhabit shallow seagrass beds in the estuaries where
they were spawned (Tabb, 1966; McMichael and Peters,
1989). Adult spotted seatrout spawn from April to
October in estuaries throughout Florida.This species
matures at one to 4 years of age throughout its range
(Klima and Tabb, 1959; Lorio and Perret,1980). Mature,
reproductively active spotted seatrout less than 1 year
of age (age 0) have been reported from Florida waters
(Crabtree and Adams, 1998). Spotted seatrout grow to
256–287 mm SL by the end of their first year, and
females are generally larger than males at any given
age (Murphy and Taylor, 1994).The maximum observed
age for this species in Florida differs between estuar-
ine areas, ranging from 5 to 9 years for males and from
6 to 8 years for females (Murphy and Taylor, 1994).
Juvenile spotted seatrout feed on mysids, penaeoid
shrimp, and small fishes (Darnell, 1958; Carr and
Adams, 1973; McMichael and Peters, 1989). Adults feed
on shrimp and a wide variety of larger fishes, includ-
ing mullet, Mugil spp.; pigfish, Orthopristis chrysoptera;
pinfish, Lagodon rhomboides; anchovies, Anchoa spp.;
mojarras, Eucinostomus spp.; silversides, Menidia spp.;
Atlantic croaker, Micropogonias undulatus; silver seatrout,
Cynoscion nothus; and occasionally other spotted
seatrout (Darnell, 1958; Adams et al. 1973; FWC-FMRI,
unpublished data).
This species supports major recreational and com-
mercial fisheries throughout Florida. In 2000, a total of
3,275,700 pounds of spotted seatrout were landed recre-
ationally and commercially from Florida waters, with
greater than 80% being landed from the gulf coast
(FWC-FMRI, 2001; NMFS, Fisheries Statistics and Eco-
nomic Division, personal communication). Greater
than 95% (by weight) of Florida landings are from the
recreational fishery. The greatest fisheries-related
22 FMRI Technical Report TR-9
Adams et al. Mercury Levels in Marine and Estuarine Fishes of Florida 1989–2001
impact upon spotted seatrout has historically been
from recreational fishing activities (Gilmore, 1995).
Spotted seatrout used in the mercury analyses (n
= 786) were collected from the Indian River Lagoon,
Cedar Key, Tampa Bay, Choctawhatchee Bay, Florida
Keys/Florida Bay, Charlotte Harbor, and Apalachico-
la Bay. A limited number of fish were collected from
the Everglades (n = 8) and from northeast Florida (n =
5). Standard lengths (SL) of sampled fish ranged from
143 to 680 mm. Mercury levels detected in spotted
seatrout from Florida waters were variable, which may
be related to the variable diet and growth rate of this
species (Rider and Adams, 2000).Total mercury levels
for individual fish ranged from 0.02 to 2.50 ppm
(Appendix Table). The mean total mercury levels in
most study areas were similar, ranging from 0.33 ppm
in Apalachicola Bay (median = 0.28 ppm) to 0.47 ppm
in the Indian River Lagoon (median = 0.41 ppm). The
mean total mercury level was comparatively higher in
the Florida Keys/Florida Bay (mean = 0.64 ppm; medi-
an = 0.43 ppm), but was only significantly higher than
levels from fish from Apalachicola Bay and Tampa Bay
(Kruskal-Wallis test, P < 0.001; Dunn’s method, P <
0.05). Approximately 33% of all spotted seatrout test-
ed from Florida waters had total mercury levels greater
than or equal to 0.5 ppm. Although the size of fish
with mercury levels greater than or equal to 0.5 ppm
was variable (252–680 mm SL; mean = 412 mm SL ± 81.1
SD), overall, these fish were significantly larger than
those with total mercury levels less than 0.5 ppm
(Mann-Whitney rank sum test, P < 0.0001).
Of the 786 spotted seatrout collected from Florida
waters, 366 fish (approximately 47%) were of legal or
harvestable size (326–437 mm SL; 381–508 mm TL,
although one fish over 508 mm TL is allowed).Total mer-
cury levels of legal-size fish ranged from 0.03 to 2.3 ppm.
Total mercury levels of legal-size spotted seatrout were
not significantly different from those of all other fish
outside the legal “slot limit”(437 mm SL; 508 mm TL)
(Mann-Whitney rank sum test, P > 0.1). Anglers in
Florida are currently allowed one spotted seatrout
greater than the upper size of the “slot limit” (FWC,
2002). Of the 164 spotted seatrout analyzed in this
study that were larger than the upper size of the “slot
limit,” a total of 99 (approximately 60%) had mercury
levels greater than or equal to 0.5 ppm.
Analysis of spotted seatrout indicated significant
positive correlations between total mercury level and
fish length (P < 0.0001) in the Indian River Lagoon,
Cedar Key,Tampa Bay, Choctawhatchee Bay, and Char-
lotte Harbor. The relationship between total mercury
level and fish length was not as clear for fish collect-
ed from Florida Keys/Florida Bay (P > 0.001) or from
Apalachicola Bay (P > 0.01). Within the distribution of
spotted seatrout from Florida Keys/Florida Bay, a group
was isolated that contained higher levels of mercury
than the other fish sampled from this area did. The
majority of these “higher-level” fish were collected
specifically from the Deer Key area, located in north-
eastern Florida Bay within the boundaries of the
Everglades National Park (latitude ~25°11.113′N; lon-
gitude ~80°32.202′W). The spotted seatrout collected
from this area of Florida Bay contained comparative-
ly high levels, which may indicate this is a localized area
where available mercury is high. Small-scale location
effects may contribute to larger-scale regional differ-
ences in mercury, as was detected for this species in
Florida Keys/Florida Bay. Elevated mercury levels in
spotted seatrout from Florida Bay have been docu-
mented (Adams and McMichael, 2001; Strom and
Graves, 2001), and additional investigations in this
area are ongoing.
After reviewing the levels of mercury for this
species, the Florida Department of Health released a
health advisory on 6 October 1995 (HRS, 1995) urging
limited consumption of spotted seatrout from Florida
Keys/Florida Bay and from Charlotte Harbor. In Jan-
uary 2003, DOH issued an updated health advisory
recommending limited consumption of spotted
seatrout greater than 20 inches, or approximately 508
mm TL, from all coastal waters of Florida and limited
consumption of all seatrout from Florida Keys/Flori-
da Bay (DOH, 2003).
Spot
Leiostomus xanthurus
Spot, Leiostomus xanthurus, occur in most estuarine
and coastal waters of Florida but are rare in Florida Bay
and the lower Florida Keys (Chao, 1978; Darovec, 1983;
FWC-FMRI, 1991, 1992, 1993, 1994, 1995). Spawning
typically occurs in offshore waters from October to
March (Springer and Woodburn, 1960; Warlen and
Chester, 1985). Sexual maturity is reached at 170–210
mm TL (approximately 133–168 mm SL) at 2–3 years of
age (Hildebrand and Schroeder, 1928; Music, 1974;
Chao and Musick, 1977). Spot attain a total length of
100–115 mm by age 1 (Welsh and Breder, 1923; Wein-
stein and Walters, 1981) and can live for up to five
FMRI Technical Report TR-9 23
Mercury Levels in Marine and Estuarine Fishes of Florida 1989–2001 Adams et al.
years (DeVries, 1982). Juvenile and adult spot feed on
infaunal and epibenthic invertebrates (Hales and Van
Den Avyle, 1989).
Spot are abundant demersal fish and have histori-
cally supported both a commercial fishery and a minor
recreational fishery in Florida waters.The elimination of
use of entangling gear in July 1995 within Florida waters
has significantly reduced or eliminated the traditional
commercial fishery for spot (McRae et al., 1997). A total
of 92,934 pounds of spot were landed in Florida during
2000, with 82% landed by the commercial fishery (Mur-
phy et al., 2001). The majority (75%) of recorded landings
in Florida during 2000 were from the Atlantic coast. Esti-
mates of the recreational landings of this species in
Florida are uncertain (Murphy and Muller, 1995; Mur-
phy et al., 2000). In other portions of the south Atlantic
region, spot are considered popular sport fish, and recre-
ational landings may exceed commercial landings (Hales
and Van Den Avyle, 1989). Spot are also widely used as
live bait along the Atlantic coast of Florida, primarily for
common snook, Centropomus undecimalis, and other large
sport fishes (FWC-FMRI, unpublished data). Spot were
collected in the Indian River Lagoon (n = 21), Tampa
Bay (n = 19) and Choctawhatchee Bay (n = 12). Addi-
tionally, nine spot were collected from northeast Florida,
six spot were collected from northern Sarasota Bay, and
four spot were sampled from Charlotte Harbor. Seven-
ty-one spot, ranging from 101 to 313 mm standard length,
were analyzed for total mercury.Total mercury levels for
individual fish ranged from 0.02 to 0.46 ppm (Appendix
Table). Mean total mercury levels were low in all study
areas and were similar in the Indian River Lagoon (mean
= 0.12 ppm; median = 0.11 ppm),Tampa Bay (mean = 0.11
ppm; median = 0.11 ppm), and Choctawhatchee Bay
(mean = 0.16 ppm; median = 0.14 ppm).
Analyses of spot indicated a positive correlation
between total mercury level and fish length in the
Indian River Lagoon (P < 0.0001). Overall, total mercury
levels for this species from Florida waters were low. No
spot tested from Florida waters had total mercury lev-
els greater than or equal to 0.5 ppm.
Southern kingfish
Menticirrhus americanus
Three species of kingfish are found in Florida, but the
southern kingfish, Menticirrhus americanus, is the most
common inshore species (FWC-FMRI, 1991–2000).
Kingfish are often referred to as “whiting.” Southern
kingfish principally occur in estuarine and nearshore
areas over a wide array of habitat types (Irwin, 1970;
McMichael and Ross, 1987; FWC-FMRI, 1991–2000).
Spawning occurs principally in offshore waters (Irwin,
1970) from April to August in Florida (Reid, 1954), but
year-round spawning has been documented in south-
ern Florida waters (Jannke, 1971). Southern kingfish
grow rapidly, and males mature during the first year
at approximately 140–180 mm TL (110–145 mm SL)
and females at approximately 150–220 mm TL (120–180
mm SL) (Smith and Wenner, 1985; Harding and Chit-
tenden, 1987). Southern kingfish feed on infaunal and
epibenthic invertebrates and small fishes (McMichael,
1981; Music and Pafford, 1984).
Southern kingfish are landed commercially and
recreationally in Florida waters. Florida commercial
kingfish landings ranged between 500,000 and 1,200,000
pounds per year from 1986 to 1995, and recreational
landings ranged from 350,000 to 3,000,000 pounds per
year during the same time period (Armstrong and
Muller, 1996). A total of 1,800,000 pounds of kingfish
were landed in Florida waters during 2000 (Murphy et
al., 2001). Approximately 75% of overall kingfish land-
ings in Florida were southern kingfish (Armstrong
and Muller, 1996).
Southern kingfish ranging from 121 to 348 mm
standard length were collected in Tampa Bay (n = 25),
northeast Florida (n = 19),and the Indian River Lagoon
(n = 18). Additional southern kingfish were also sam-
pled from Charlotte Harbor (n = 7), Cedar Key (n = 6),
and Apalachicola Bay (n = 1). Mercury levels detected
in southern kingfish from Florida waters were usual-
ly low.Total mercury levels for individual fish ranged
from 0.02 to 0.78 ppm (Appendix Table). Mean total mer-
cury levels were low in Tampa Bay (mean = 0.19 ppm;
median = 0.16 ppm), in northeast Florida (mean = 0.13
ppm; median = 0.10 ppm), and in the Indian River
Lagoon (mean = 0.08 ppm; median = 0.07 ppm). Only
four southern kingfish from Florida waters (approxi-
mately 7.3%) had levels greater than or equal to 0.5
ppm.There was no apparent correlation between length
and mercury level for southern kingfish from Tampa
Bay (P > 0.1), but only a limited size range of fish was
available from this area. Additional samples from
throughout Florida are required to fully assess mercury
levels in this species.
24 FMRI Technical Report TR-9
Adams et al. Mercury Levels in Marine and Estuarine Fishes of Florida 1989–2001
Atlantic croaker
Micropogonias undulatus
Atlantic croaker, Micropogonias undulatus, are found
in estuarine and nearshore areas along Florida’s
Atlantic and gulf coasts, principally in central and
northern Florida waters. Juvenile Atlantic croaker
inhabit a wide range of estuarine habitats and move
to nearshore areas as they grow. Adult Atlantic croak-
er occur in nearshore areas from the surf zone out to
continental shelf waters and also seasonally inhabit
estuarine areas in central and northern Florida. Atlantic
croaker have a protracted spawning period, extending
from July to December in Chesapeake Bay and Mid-
Atlantic Bight (Barbieri et al., 1994b; Morse, 1980) and
possibly into early spring in both the South Atlantic
Bight (Warlen, 1982) and Gulf of Mexico (Pearson, 1929;
Gunter, 1938b). Little is known regarding the repro-
ductive biology of this species in Florida, but spawning,
inferred from the timing of recruitment of young-of-
the-year fish, occurs during fall and winter. Atlantic
croaker mature by the end of the first year or during
the second year (Barbieri et al., 1994b) and can live for
up to 8 years (Barger, 1985; Barbieri et al., 1994a). The
feeding habits of this species can change during their
lifetime, but a variety of benthic invertebrates are
important in their diet (Darnell, 1958, 1961).
A total of 409,443 pounds of Atlantic croaker were
recreationally and commercially landed in Florida dur-
ing 2000, with the majority (67%) of landings from the
Atlantic coast (Murphy et al., 2001). Atlantic croaker are
also used extensively as live bait by recreational fish-
ermen targeting a variety of species. Along the
central-east coast of Florida, Atlantic croaker are high-
ly sought after and are often the preferred live bait used
in the recreational fishery for common snook, Cen-
tropomus undecimalis.
Atlantic croaker were collected from northeast
Florida (n = 23) and the Indian River Lagoon (n = 21),
with a limited number of fish collected from Tampa Bay
(n = 2) and Cedar Key (n = 1). Standard lengths of the
47 Atlantic croaker in this study ranged from 89 to 385
mm. Mercury levels detected in Atlantic croaker were
low. Total mercury levels for individual fish ranged
from 0.02 to 0.18 ppm (Appendix Table). The mean
total mercury level for this species in northeast Flori-
da was 0.06 ppm (median = 0.05 ppm).The mean total
mercury level for Atlantic croaker in the Indian River
Lagoon was also 0.06 ppm (median = 0.04 ppm). Analy-
sis of Atlantic croaker from the Indian River Lagoon
revealed a positive correlation between total mercury
level and fish length (P < 0.01).There was no apparent
correlation between length and mercury level for fish
from northeast Florida (P > 0.1), but only a limited size
range of fish was available from this area. All Atlantic
croaker tested from Florida waters had a mercury level
less than 0.2 ppm.
Black drum
Pogonias cromis
Black drum, Pogonias cromis, inhabit estuarine and
nearshore waters of the gulf and Atlantic coasts of
Florida and range from New England to Argentina
(Bigelow and Schroeder, 1953). Distinct subpopula-
tions of black drum occur in the Gulf of Mexico and
western Atlantic Ocean (Gold and Richardson, 1998).
Results from tagging studies have indicated that black
drum do not frequently move long distances between
estuaries (Topp, 1963; Beaumariage, 1964, 1969; Osburn
and Matlock, 1984), although this species is capable of
extensive, long-range migrations (Murphy et al., 1998).
Black drum spawn during the winter and early
spring (Murphy and Taylor, 1989) in estuaries and open
coastal waters (Simmons and Breuer, 1962; FWC-FMRI,
unpublished data). Black drum are multiple spawners
and produce large numbers of eggs during each spawn-
ing event, with the mean batch fecundity of an
average-size female (6.1 kg total weight) estimated to
be 1.6 million hydrated oocytes (Fitzhugh et al., 1993).
Juvenile black drum are found in estuarine creek and
river habitats, typically over unvegetated mud sub-
strates (Pearson, 1929; Peters and McMichael, 1990).
Adults inhabit estuaries and nearshore shelf waters
(Sutter et al., 1986). Males begin maturing when they
are 366–486 mm SL (2–5 years old), and females typi-
cally begin maturing at sizes greater than 538 mm SL
FMRI Technical Report TR-9 25
Mercury Levels in Marine and Estuarine Fishes of Florida 1989–2001 Adams et al.
(approximately 5 years old) (Murphy and Taylor,1989;
Nieland and Wilson, 1993). This large sciaenid can
grow to 66 kg (Bigelow & Schroeder, 1928) and have a
lifespan of approximately 60 years (Murphy and Tay-
lor, 1989; Jones and Wells, 1998).
Juvenile black drum feed on bivalves, gastropods,
amphipods, shrimps, and small fishes (Music and Paf-
ford, 1984; Peters and McMichael, 1990). Adults
consume bivalves, shrimps, crabs, and related benth-
ic prey (Music and Pafford, 1984; FWC-FMRI,
unpublished data). Black drum have strong pharyngeal
teeth capable of crushing hard invertebrate shells.
Stomachs of black drum examined during this mercury
study often contained large amounts of crushed bivalve
shell material and crab exoskeletons.
Black drum are caught by recreational and com-
mercial fishermen throughout Florida, but the majority
of fish are landed along the northeast and central
Atlantic coast. Recreational fishermen accounted for
98% of the total landings of this species during 2000
(Murphy et al., 2001). The black drum fishery along the
Atlantic coast of Florida typically targets small, young
fish (FWC-FMRI, unpublished data), but large (>800
mm SL), older fish are landed seasonally by recre-
ational fishermen in this region. A total of 1,342,343
pounds of black drum were landed in Florida during
2000, which was more than double the total landed in
1999 (Murphy et al., 2001).
A total of 71 black drum from Florida waters were
used in mercury analyses. Black drum were princi-
pally collected in the Indian River Lagoon area and
adjacent nearshore waters (n = 36) and Tampa Bay (n
= 23). Standard lengths of sampled fish ranged from 193
to 1,049 mm. Mercury levels detected in black drum
from Florida waters were typically low. Total mercury
levels for individual fish ranged from 0.01 to 0.65 ppm.
Mean total mercury levels were 0.14 ppm (median =
0.13 ppm) in the Indian River Lagoon area and 0.24 ppm
(median = 0.21 ppm) in Tampa Bay (Appendix Table).
Approximately 91% of the black drum collected for
mercury analysis were larger than the legal minimum
size for this species in Florida (285 mm SL; 356 mm TL).
Only one black drum tested contained a total mer-
cury level greater than or equal to 0.5 ppm. This fish
was the largest individual analyzed in this study (a
1049 mm SL adult collected in the nearshore waters
adjacent to the Indian River Lagoon). Analyses indi-
cated significant positive correlations between total
mercury level and fish length (P < 0.0001) for black
drum from the Indian River Lagoon area and from
Ta mpa Bay. Although there was a positive correlation
between mercury level and fish size, mercury levels in
black drum collected in Florida, even in large, mature
individuals, were usually low.
Red drum
Sciaenops ocellatus
The red drum, Sciaenops ocellatus, inhabits estuarine and
nearshore waters of the gulf and Atlantic coasts of
Florida. Adult red drum spawn during late summer and
fall. Spawning occurs near inlets, bay entrances, inside
estuaries, and in nearshore continental shelf waters
(Mercer, 1984; Peters and McMichael, 1987). Red drum
in the Indian River Lagoon system on the Atlantic
coast of Florida are also capable of spawning in estu-
arine waters far from oceanic inlets (Murphy and
Taylor, 1990; Johnson and Funicelli, 1991). Juvenile red
drum are found in a wide range of estuarine habitats,
including shallow seagrass beds, unvegetated mud-
sand bottom, rivers, canals, boat basins, and creeks
(Tabb, 1966; Mercer, 1984; Peters and McMichael, 1987;
Adams and Tremain, 2000). Juveniles and larger
subadults may also move into nearshore continental
shelf waters during winter months (Mercer, 1984).
Adults inhabit estuaries and nearshore shelf waters
(Mercer, 1984; Murphy and Taylor, 1990). Males mature
when they are 292–706 mm SL (1–3 years old), and
females mature at 477–798 mm SL (3–6 years old) (Mur-
phy and Taylor, 1990).Red drum grow rapidly through
age 5 and then growth slows as the fish approach
maturity. Similar growth rates have been observed for
red drum on the gulf and Atlantic coasts of Florida
(Murphy and Taylor, 1990). The maximum observed
ages for this species in Florida were 24 years on the gulf
coast and 33 years on the Atlantic coast (Murphy and
Taylor, 1990). Red drum have been reported to live up
to 56 years elsewhere along the U.S. Atlantic coast
(Ross et al., 1995).
Juvenile red drum feed on mysids, amphipods,
polychaetes, and shrimp (Peters and McMichael, 1987).
As juvenile red drum grow, they shift to the adult diet
of shrimp, crabs, and fishes (Miles, 1950; FWC-FMRI,
unpublished data).
Red drum are highly sought by recreational fish-
ermen throughout Florida. This species was landed
commercially until 1989, when regulatory actions made
the sale of native red drum illegal. Landings of red
drum in Florida have been generally stable since 1989,
when current fisheries regulations were issued (Mur-
phy et al., 2001). Florida-wide recreational landings
26 FMRI Technical Report TR-9
Adams et al. Mercury Levels in Marine and Estuarine Fishes of Florida 1989–2001
Figure 7. Relationship between total mercury level (ppm) and stan-
dard length (mm) of red drum, Sciaenops ocellatus, from the
Indian River Lagoon, Florida.The dashed line represents the 0.5-
ppm threshold level.
totaled 553,320 fish (2,540,076 pounds) in 2000 (Murphy
et al., 2001).
Red drum (n = 682) used in mercury analyses were
principally collected in Tampa Bay and adjacent coastal
waters, Indian River Lagoon, Cedar Key, Apalachico-
la Bay, Florida Keys/Florida Bay, and Charlotte Harbor.
Additional red drum were also collected in Choc-
tawhatchee Bay (n = 15) and the Florida Everglades (n
= 15). Standard lengths (SL) of sampled fish ranged
from 180 to 1,070 mm. Mercury levels detected in red
drum from Florida waters were variable but usually low
in most areas. Total mercury levels for individual fish
ranged from 0.02 to 3.60 ppm. The mean total mer-
cury levels in all fish (juveniles and adults) from Florida
study areas except Tampa Bay ranged from 0.18 ppm
in Cedar Key (median = 0.18 ppm) to 0.48 ppm Flori-
da Keys/Florida Bay (median = 0.35 ppm); the mean
total mercury level from the Tampa Bay area was 1.10
ppm (median = 0.98 ppm) (Appendix Table). The high-
er mean total mercury level observed for fish from the
Ta mpa Bay area was related to the fact that more than
59% of these fish were large (>565 mm SL), reproduc-
tively active adults from offshore waters. Of the red
drum collected for mercury analysis, 257 fish (approx-
imately 38%) were of legal, or slot-limit, size (374–565
mm SL; 457–689 mm TL).Total mercury levels of legal-
size fish ranged from 0.02 to 2.70 ppm. Mean total
mercury levels of legal-size red drum were relatively
low (mean = 0.17–0.30 ppm) in most study areas test-
ed, but the mean total level in Florida Keys/Florida Bay
(mean = 0.52 ppm; median = 0.35 ppm) was higher.
Figure 8. Relationship between total mercury level (ppm) and stan-
dard length (mm) of red drum, Sciaenops ocellatus, from offshore
waters adjacent to Tampa Bay,Florida.The dashed line represents
the 0.5-ppm threshold level.
Overall, approximately 8% of legal-size red drum had
mercury levels greater than or equal to 0.5 ppm.
One hundred and thirty-nine large, reproductively
active, adult red drum were collected from coastal
waters offshore of the Tampa Bay area. These adult
fish ranged from 561 to 992 mm SL (mean = 761 mm
SL), and all but one of these fish were larger than 565
mm SL (the upper size of the “slot limit”for Florida red
drum).Total mercury levels for individual offshore red
drum ranged from 0.30 to 3.60 ppm. The mean total
mercury level for these fish was 1.67 ppm (median =
1.70 ppm). Approximately 94% (n = 131) of all offshore
red drum adults tested contained levels greater than
or equal to 0.5 ppm, and 64% (n = 89) contained levels
greater than or equal to 1.5 ppm. All offshore adult red
drum with high mercury levels (≥1.5 ppm) were 670 mm
SL or larger in length.
Analysis indicated significant correlations between
total mercury level and fish length for red drum from
the Tampa Bay area (P < 0.0001), Cedar Key (P < 0.0001),
the Indian River Lagoon (P < 0.0001) (Figure 7) and
Apalachicola Bay (P < 0.001). No significant correlation
was detected between total mercury level and fish
length for red drum from the Florida Keys/Florida Bay
area (P > 0.01). Red drum collected specifically from off-
shore waters near the Tampa Bay area displayed a
significant positive correlation between total mercury
levels and fish length (P < 0.0001) (Figure 8). The major-
ity of high mercury levels were found in fish larger than
or near the maximum length of the “slot limit”for this
species. With the exception of one smaller fish (527 mm
FMRI Technical Report TR-9 27
Mercury Levels in Marine and Estuarine Fishes of Florida 1989–2001 Adams et al.
SL), all red drum with total mercury levels greater
than or equal to 1.5 ppm were large fish (mean = 791
mm SL) that would not be consumed by humans
because of current size regulations in Florida.
In January 2003, DOH issued a health advisory
recommending limited consumption of red drum from
Florida Keys/Florida Bay (DOH, 2003).
Striped mullet
Mugil cephalus
The striped mullet, Mugil cephalus, is one of the most
abundant and widespread inshore species in the south-
eastern United States (Odum, 1970) and occurs in a
variety of Florida estuarine and coastal water habitats
(Collins, 1985; FWC-FMRI, 1991–2000). Only one genet-
ic stock of this species occurs in Florida coastal waters
(Campton and Mahmoudi, 1991). Spawning typically
occurs from October to February (Anderson, 1958).
Although inshore spawning has been reported (Bred-
er, 1940), the majority of spawning has been
documented in offshore waters (Anderson, 1958; Arnold
and Thompson, 1958; Finucane et al., 1978). Females
reach sexual maturity at approximately 2–3 years of age
(Leard et al., 1995). Striped mullet feed on epiphytic and
benthic microalgae, macrophyte detritus, and inor-
ganic sediment particles (Collins, 1981, 1985).
This economically and ecologically important
species is harvested by commercial and recreational
fishermen throughout Florida. A total of 10,496,936
pounds of striped mullet were landed in Florida dur-
ing 2000 (FWC-FMRI, 2001; NMFS, Fisheries Statistics
and Economic Division, personal communication).
Striped mullet are also widely used as live bait or cut
bait throughout Florida (FWC-FMRI Angler Interview
data, unpublished).
Striped mullet used in mercury analyses were col-
lected mostly from Tampa Bay (n = 28), Cedar Key (n
= 15), and the Indian River Lagoon (n = 14). Addition-
al striped mullet were sampled from Charlotte Harbor
(n = 7), Choctawhatchee Bay (n = 4), and the Florida
Keys/Florida Bay (n = 3).The standard length of these
fish ranged from 155 to 469 mm. Mercury levels detect-
ed in striped mullet from Florida waters were usually
low. Total mercury levels for individual fish ranged
from 0.01 to 0.78 ppm and were similar in Tampa Bay
(mean = 0.08 ppm; median = 0.04 ppm), Cedar Key
(mean = 0.02 ppm; median = 0.02 ppm), and the Indi-
an River Lagoon (mean = 0.06 ppm; median = 0.04
ppm) (Appendix Table). Analysis of striped mullet
from Tampa Bay suggested that there was no signifi-
cant correlation between total mercury level and fish
length (P < 0.1). There were not enough samples of
striped mullet from the other study areas for us to
determine relationships between mercury levels and
fish size. Only one striped mullet tested from Florida
waters (collected in Tampa Bay) had total mercury lev-
els greater than or equal to 0.5 ppm.
Great barracuda
Sphyraena barracuda
Great barracuda, Sphyraena barracuda, occur in all trop-
ical and subtropical seas except the eastern Pacific
(deSylva, 1963). In Florida, barracuda are found in
estuarine, nearshore, and offshore waters along the
Atlantic and the gulf coasts, with highest abundances
in the southern areas of the state. Juvenile barracuda
occupy nearshore and estuarine seagrass or mangrove
habitats but presumably move offshore at maturity
(deSylva, 1963; Blaber, 1982; FWC-FMRI, 1991–2001).
Adults are found principally around coral reefs, rock
outcroppings, or artificial structures (Paterson, 1998).
Spawning is thought to occur during the spring and
summer in offshore waters (deSylva, 1963; Blaber, 1982;
FWC-FMRI, unpublished data). Both male and female
barracuda mature at approximately age 2 (FWC-FMRI,
unpublished data). Barracuda feed almost entirely on
fish throughout their life history (deSylva, 1963;
Williams, 1965; Fahs, 1976; Schmidt, 1989).
Although great barracuda have been associated
with ciguatera toxin poisonings in the region (Stewart,
1990 and references therein), this species is landed
recreationally and commercially in Florida waters. In
the recreational fishery, a total of 624,940 pounds of
great barracuda were landed on the Florida Atlantic
coast and 258,611 pounds were landed on the Florida
gulf coast during 2000 (NMFS, Fisheries Statistics and
Economic Division, personal communication). A total
of 126,910 pounds of great barracuda were landed by
the commercial fishery in Florida waters during 2000
(FWC-FMRI, 2001).
The majority of the 85 great barracuda analyzed in
this study were collected from the Florida Keys/Flori-
da Bay (n = 62) and the Indian River Lagoon (n = 19).
28 FMRI Technical Report TR-9
Adams et al. Mercury Levels in Marine and Estuarine Fishes of Florida 1989–2001
Standard lengths of fish sampled ranged from 119 to
1,096 mm. Total mercury levels for individual fish
ranged from 0.08 to 3.10 ppm. The mean total mer-
cury level for great barracuda from the Florida
Keys/Florida Bay was 0.87 ppm (median = 0.72 ppm).
The mean total mercury level for fish from the Indian
River Lagoon was lower (mean = 0.16 ppm; median =
0.16 ppm); however, comparatively smaller fish (mean
= 358 mm SL; range = 213–488 mm SL) were examined
from this area. Fish collected from the Florida
Keys/Florida Bay area were larger and covered a broad-
er size range (mean = 628 mm SL; range = 119–1096 mm
SL) than those examined from the Indian River Lagoon.
Analysis of great barracuda from the Florida
Keys/Florida Bay area indicated a significant positive
correlation between total mercury level and fish length
(P < 0.0001), which indicates that mercury levels tend
to increase as great barracuda grow. Approximately
56% of great barracuda analyzed from Florida waters
contained mercury levels greater than or equal to 0.5
ppm. Eight percent of great barracuda analyzed from
Florida waters contained mercury levels greater than
or equal to 1.5 ppm. All fish containing total mercury
at or above 1.5 ppm were large individuals (750–1,096
mm SL).
In January 2003, DOH issued a health advisory
recommending limited consumption of great bar-
racuda from Florida Keys/Florida Bay (DOH, 2003).
Wahoo
Acanthocybium solanderi
The wahoo, Acanthocybium solanderi, is an offshore
pelagic species with a global distribution in tropical and
subtropical waters. The biology of wahoo is not well
understood, but FWC-FMRI is currently examining
the life history characteristics of this species in Flori-
da waters. Wahoo in the subtropical Atlantic and Gulf
of Mexico are thought to spawn during summer months
(Wollam, 1969; Hogarth, 1976), but preliminary data
from the northern Gulf of Mexico and Bahamas sug-
gests the possibility that limited spawning occurs in the
early spring (Brown-Peterson et al., 2000).Very little is
known regarding the abundance and distribution of
wahoo, but they are caught year round in Florida
waters (SAFMC, 1998), with peak catches occurring
during summer months (FWC-FMRI, 2001). Wahoo
can attain a length of approximately 2,100 mm and a
total weight of 83 kg (FWC-FMRI, unpublished data).
Preliminary results from a recent genetics study
strongly suggest that wahoo in the Gulf of Mexico and
off the U.S. Atlantic coast comprise one population (J.
Franks, personal communication, Gulf Coast Research
Laboratory, Ocean Springs, MS). Wahoo feed princi-
pally on pelagic fishes (e.g., flying fish, Cypselurus spp.;
ballyhoo, Hemiramphus brasiliensis; porcupinefish,
Diodon hystrix) and, to a lesser extent, invertebrates
(e.g., squids) (Manooch and Hogarth, 1983; FWC-FMRI,
unpublished data).
Wahoo are an important recreational and com-
mercial species in Florida waters. In the recreational
fishery, a total of 441,385 pounds of wahoo were land-
ed on the Florida Atlantic coast and 92,620 pounds
were landed on the Florida gulf coast during 2000
(NMFS, Fisheries Statistics and Economic Division,
personal communication). A total of 55,003 pounds of
wahoo were landed by the commercial fishery in Flori-
da waters during 2000 (FWC-FMRI, 2001).The majority
of commercially caught wahoo are landed as inciden-
tal catch from fisheries targeting other pelagic species
(SAFMC, 2000).
A total of 61 wahoo were collected for mercury
analysis from offshore waters of the Florida Atlantic and
Gulf coasts.The majority of fish were collected in off-
shore waters adjacent to the Indian River Lagoon (n =
30) and offshore waters adjacent to Apalachicola Bay
(n = 16). All wahoo sampled were of harvestable size,
ranging from 845 to 1,338 mm SL.Total mercury levels
for individual fish ranged from 0.04 to 1.40 ppm. The
mean total mercury level for fish collected offshore
from the Indian River Lagoon area was 0.27 ppm (medi-
an = 0.23 ppm). Eighteen percent of all wahoo tested
from Florida had total mercury levels greater than or
equal to 0.5 ppm, and no wahoo contained total mer-
cury levels greater than 1.5 ppm. Analysis of wahoo
from offshore waters adjacent to the Indian River
Lagoon indicated a significant positive correlation
between total mercury level and fish length (P < 0.0001).
In January 2003, based on additional data from
south Florida, DOH issued a health advisory recom-
mending limited consumption of wahoo from Florida
Keys/Florida Bay (DOH, 2003).
King mackerel
Scomberomorus cavalla
The king mackerel, Scomberomorus cavalla, is a coastal
FMRI Technical Report TR-9 29
Mercury Levels in Marine and Estuarine Fishes of Florida 1989–2001 Adams et al.
pelagic species that is widely distributed along the
Atlantic and gulf coasts. In Florida, the majority of
spawning occurs from May through September, but
there is some evidence that spawning occurs as early
as April and as late as October (McEachran et al., 1980;
Finucane et al., 1986). Little is known regarding the dis-
tribution and abundance of juvenile king mackerel,
although juveniles have been documented to occur in
both nearshore and offshore areas (Wollam, 1970;
Dwinell and Futch, 1973; Collins and Wenner, 1988).
Maximum age observed was 12 years for males and 14
years for females (Johnson et al., 1983). Males mature
at 4 years of age and approximately 718 mm fork
length (FL) (Beaumariage, 1973). Females mature at 5–6
years of age and at 850–899 mm FL (Finucane et al.,
1986). King mackerel can attain a length of 1,725 mm
FL and a total weight of 37.2 kg (Beaumariage, 1973).
King mackerel feed principally on schooling fishes
(e.g., ballyhoo, Hemiramphus brasiliensis; scaled sar-
dine, Harengula jaguana; and Atlantic thread herring,
Opisthonema oglinum) and various invertebrates,
including shrimp and squid (Beaumariage, 1973; Salo-
man and Naughton, 1983).
The king mackerel is an important commercial
and recreational species throughout Florida. A total of
8,116,039 pounds of king mackerel were landed in
Florida during 2000 (FWC-FMRI, 2001; NMFS, Fish-
eries Statistics and Economic Division, personal
communication). Historical records indicate that
approximately 90% of the total United States catch of
this species has been landed in Florida (Godcharles
and Murphy, 1986). Migration patterns and recent
genetic studies indicate that in the southeastern Unit-
ed States, king mackerel form two stocks, one along
the Atlantic coast and one in the Gulf of Mexico
(Sutherland and Fable, 1980; Sutter et al., 1991; John-
son et al., 1993; Gold et al., 1996).
A total of 142 king mackerel were collected in Flori-
da for mercury analysis, with the majority being from
offshore waters of the gulf coast of Florida. Fork lengths
of fish sampled ranged from 620 to 1,378 mm, and the
mean size for all Florida fish was 1,020 mm. All king
mackerel sampled were of legal or harvestable size.
Mercury levels detected in king mackerel from Flori-
da waters were usually high. Total mercury levels for
individual fish ranged from 0.19 to 4.00 ppm.The mean
total mercury level for king mackerel from offshore
waters of the gulf coast in the Tampa Bay region was
1.56 ppm (median = 1.35 ppm). Approximately 82% of
all king mackerel tested from Florida waters had total
mercury levels greater than or equal to 0.5 ppm, and
approximately 46% had total mercury levels greater
than or equal to 1.5 ppm. King mackerel with high
mercury levels (>1.5 ppm) were typically large indi-
viduals (mean = 1,156 mm FL). Analysis of king mack-
erel from central gulf coast waters indicated a
significant positive correlation between total mercury
level and fish length (P < 0.0001) (Figure 9).
Figure 9. Relationship between ln total mercury level (ppm) and
fork length (mm) of king mackerel, Scomberomorus cavalla,
from the central Florida gulf coast.The dashed line represents the
antilog equivalent of the 0.5-ppm threshold level.
A similar study conducted by the National Marine
Fisheries Service (NMFS) also detected elevated lev-
els of mercury in king mackerel collected in the
southeastern United States (Meaburn, 1978). After
reviewing results concerning fish from the gulf coast
of Florida, the Florida Department of Health (HRS,
1996) released a health advisory on 4 June 1996 urging
limited consumption of king mackerel from Florida
waters, based on fish size. The advisory recommend-
ed limited consumption of king mackerel in the 838–990
mm FL size-class and no consumption of fish greater
than 990 mm FL. No advisory was issued for king
mackerel smaller than 838 mm FL. On 23 March 2000,
the states of Florida, Georgia, North Carolina, and
South Carolina issued a joint health advisory regard-
ing high levels of mercury in large king mackerel from
the southeastern United States coastline (DOH, 2000).
The consumption limits reflected those outlined in
Florida’s 1996 advisory but included all Atlantic and
Gulf of Mexico waters in the southeastern United
States. In January 2003, DOH issued an updated health
advisory recommending no consumption of large king
mackerel (>39 inches, or approximately 990 mm FL),
and limited consumption of king mackerel measuring
33 to 39 inches, or approximately 838 to 990 mm FL, from
all coastal waters of Florida (DOH, 2003).
30 FMRI Technical Report TR-9
Adams et al. Mercury Levels in Marine and Estuarine Fishes of Florida 1989–2001
Spanish mackerel
Scomberomorus maculatus
Spanish mackerel, Scomberomorus maculatus, inhabit
Florida’s coastal and estuarine waters. Spawning occurs
from mid-spring through summer (Finucane and
Collins, 1986; Schmidt et al., 1993). Juvenile Spanish
mackerel use estuaries and nearshore, open-beach
waters as nursery areas (Godcharles and Murphy, 1986).
The maximum age has been determined to be 6 years
for males and 11 years for females (Schmidt et al., 1993).
This species matures during the first year; females
mature at 288–450 mm FL (approximately 266–417 mm
SL) and males at 209–336 mm FL (approximately 193–311
mm SL) (Schmidt et al., 1993). Spanish mackerel can
attain a length of 770 mm FL (approximately 715 mm
SL) and a total weight of 4.8 kg (Beardsley and Richards,
1970). Spanish mackerel feed on pelagic fish (e.g., scaled
sardine, Harengula jaguana; Atlantic threadfin herring,
Opisthonema oglinum; anchovies, Anchoa spp.; and men-
haden, Brevoortia spp.) and small invertebrates,
including shrimp and squid (Miles and Simmons, 1951;
Klima, 1959; Saloman and Naughton, 1983).
The Spanish mackerel supports major commer-
cial and recreational fisheries throughout Florida. A
total of 5,592,389 pounds of Spanish mackerel were
landed in Florida during 2000 (FWC-FMRI, 2001; NMFS,
Fisheries Statistics and Economic Division, personal
communication). Since 1950, more than 92% of the total
U.S. catch has been landed in Florida (Trent and Antho-
ny, 1979). Concerns regarding overfishing have recently
prompted size limits, daily bag limits, and recreation-
al/commercial landings quotas (SAFMC, 1988).
Migration and spawning patterns indicate that in the
southeastern U.S., this species has an Atlantic stock
and one or more Gulf of Mexico stocks (Skow and Chit-
tenden, 1981; Collette and Russo, 1984; SAFMC, 1988).
A total of 389 Spanish mackerel were collected for
mercury analysis in Tampa Bay (n = 187), the Indian
River Lagoon and adjacent coastal waters (n = 98),
Charlotte Harbor (n = 50), and other Florida waters.
Standard lengths of fish sampled ranged from 132 to
715 mm. Mercury levels detected in Spanish macker-
el from Florida waters were relatively high. Total
mercury levels for individual fish ranged from 0.06 to
3.00 ppm. Mean total mercury levels from the three
major study areas were 0.53 ppm (median = 0.47 ppm)
in Tampa Bay, 0.32 ppm (median = 0.25 ppm) in the Indi-
an River Lagoon region, and 0.71 ppm (median = 0.62
ppm) in Charlotte Harbor (Appendix Table). Standard
lengths of Spanish mackerel collected in Charlotte
Harbor were significantly larger than those collected
from Tampa Bay or the Indian River Lagoon (Kruskal-
Wallis test, P < 0.0001; Dunn’s method, P < 0.05).There
were no significant differences between lengths of fish
collected from Tampa Bay and the Indian River Lagoon.
Mercury levels in Spanish mackerel from the Indian
River Lagoon region were lower and significantly dif-
ferent from the levels in gulf coast fish in Tampa Bay
and Charlotte Harbor (Kruskal-Wallis test, P < 0.0001;
Dunn’s method, P < 0.05).
Approximately 37% of all Spanish mackerel from
Florida waters had mercury levels greater than or
equal to 0.5 ppm.The majority (approximately 82%) of
the Spanish mackerel examined from Florida waters
were of legal size (≥283 mm SL; ≥305 mm TL). A total
of 44% of legal-sized Spanish mackerel had mercury
levels greater than or equal to 0.5 ppm. A similar study
conducted by the National Marine Fisheries Service
(NMFS) in the southeastern United States also detect-
ed elevated mercury levels in Spanish mackerel
(Meaburn, 1978). Significant positive correlations (P <
0.0001) between total mercury level and fish length
were detected for Spanish mackerel from Tampa Bay,
the Indian River Lagoon, and Charlotte Harbor.
After reviewing mercury results for this species, the
Florida Department of Health (HRS, 1995) released a
health advisory on 6 October 1995 urging limited con-
sumption of Spanish mackerel from Tampa Bay and
Charlotte Harbor waters.
Gulf flounder
Paralichthys albigutta
Gulf flounder, Paralichthys albigutta, inhabit coastal
and estuarine waters throughout Florida, often pre-
ferring sand substrates or hard bottom (Gilbert, 1986b
and references therein; FWC-FMRI, 1991–2000). Spawn-
ing occurs in offshore waters during fall and winter
(Gilbert, 1986b and references therein). This species
matures at approximately 2 years of age (Stokes, 1977)
and can attain a total length of 710 mm and a total
weight of 5 kg (Vick, 1964). Gulf flounder are oppor-
FMRI Technical Report TR-9 31
Mercury Levels in Marine and Estuarine Fishes of Florida 1989–2001 Adams et al.
tunistic predators that feed on a variety of fish and crus-
taceans (Darnell, 1958; Stokes, 1977).
The gulf flounder is a valuable recreational and
commercial species in Florida. Landings of this species
in Florida are typically grouped with the southern floun-
der, Paralichthys lethostigma, and to a lesser extent with
the summer flounder, P. dentatus (Gilbert, 1986b; Mur-
phy et al., 1994). Overall flounder landings are greatest
in the fall, and approximately two-thirds of landings
occur on the Atlantic coast (Murphy et al., 1994).
A total of 190 gulf flounder were collected from
Florida waters, with the majority collected from Char-
lotte Harbor (n = 71) and Tampa Bay (n = 65). A limited
number of gulf flounder were also collected from
Choctawhatchee Bay (n = 18), the Volusia County region
(n = 15), the Indian River Lagoon (n = 8), Florida
Keys/Florida Bay (n = 5), Apalachicola Bay (n = 5), and
other areas of Florida. Standard lengths of fish sampled
ranged from 115 to 500 mm. Mercury levels detected in
gulf flounder from Florida waters were usually low.
Total mercury levels for individual fish ranged from 0.01
to 1.10 ppm. Mean total mercury levels of gulf flounder
were similar in Tampa Bay (mean = 0.20 ppm; median
= 0.16 ppm), Charlotte Harbor (mean = 0.31 ppm; medi-
an = 0.28 ppm), Choctawhatchee Bay (mean = 0.20 ppm;
median = 0.20 ppm), and Volusia County (mean = 0.14
ppm; median = 0.11 ppm) (Appendix Table).
Analysis of gulf flounder from Tampa Bay and
Charlotte Harbor showed a positive correlation be-
tween total mercury level and fish length (P < 0.0001).
There were not enough samples of gulf flounder from
the other study areas for us to determine relationships
between mercury levels and fish size. Overall, a low per-
centage of gulf flounder tested from Florida waters
had total mercury levels greater than or equal to 0.5
ppm (Tampa Bay = 2%; Charlotte Harbor = 13%;
Choctawhatchee Bay = 0%). On a Florida-wide basis,
approximately 62% of the gulf flounder analyzed were
of legal size (≥305 mm TL or approximately 253 mm SL),
and 11% of these fish contained total mercury levels
greater than or equal to 0.5 ppm.
Southern flounder
Paralichthys lethostigma
Southern flounder, Paralichthys lethostigma, inhabit
coastal and estuarine waters along the lower Atlantic
coast of Florida and the upper gulf coast but are absent
from the southern tip of Florida (Gilbert, 1986b and ref-
erences therein; FWC-FMRI, 1991–2000). Genetic
differentiation is not extensive for this species, and
preliminary data indicate that one stock of southern
flounder occurs in the southeastern United States
(Blandon et al., 2001). Both juveniles and adults are
frequently found over mud, silt, or similar soft sub-
strates (Powell and Schwartz, 1977; Stokes, 1977).
Spawning occurs from September to April (Gunter,
1945) in waters between 20 and 60 m deep (Benson,
1982).This species matures at approximately 2 years of
age (Stokes, 1977) and can attain a total length of 762
mm (Ginsburg, 1952). Southern flounder feed on a
variety of fish and crustaceans (Reid, 1954; Darnell,
1958; Stokes, 1977).
The southern flounder is a valuable recreational
and commercial species, principally along the Atlantic
coast of Florida. Landings of this species in Florida
are typically grouped with the gulf flounder, Paralichthys
albigutta, and to a lesser extent with the summer floun-
der, P. dentatus (Murphy et al., 1994).The vast majority
of overall flounder landings on the Atlantic coast from
the recreational fishery are composed of southern
flounder, and although samples are limited, southern
flounder also appears to be the principal species in the
commercial fishery in this region (Murphy et al., 1994).
A total of 67 southern flounder were collected from
Florida waters, with the majority collected from the
Indian River Lagoon (n = 23), northeast Florida (n = 18),
and Volusia County (n = 17). A limited number of
southern flounder were also collected from Apalachico-
la Bay (n = 6) and Choctawhatchee Bay (n = 3). Standard
lengths of fish sampled ranged from 137 to 576 mm.
Mercury levels detected in southern flounder from
Florida waters were usually low. Total mercury levels
for individual fish ranged from 0.04 to 0.50 ppm. Mean
total mercury levels of southern flounder in Florida
were low and were similar in all study areas examined.
Mean total mercury levels covered a small range, from
0.08 ppm (median = 0.07 ppm) in northeast Florida to
0.18 ppm (median = 0.13 ppm) in the Indian River
Lagoon (Appendix Table).
Seventy-two percent of southern flounder ana-
lyzed in this study were of legal size (≥305 mm TL).
The total mercury content of all sublegal southern
flounder examined from Florida waters was less than
0.15 ppm. Overall, only one southern flounder tested
from Florida waters had total mercury levels greater
than or equal to 0.5 ppm.This 304-mm SL fish collected
in the Indian River Lagoon contained 0.5-ppm total
mercury. No southern flounder containing total mer-
32 FMRI Technical Report TR-9
Adams et al. Mercury Levels in Marine and Estuarine Fishes of Florida 1989–2001
cury levels greater than 0.5 ppm were recorded from
Florida waters.
Summary
Muscle tissue from a wide array of Florida marine and
estuarine fish species representing many trophic lev-
els were analyzed in this study.The majority of species
we examined contained low mercury levels. Species
with very low mean or median mercury levels tended
to be planktivores (e.g., menhaden, Brevoortia spp.),
detritivores (e.g., striped mullet, Mugil cephalus), species
whose diet is mostly invertebrates (e.g., Atlantic
stingray, Dasyatis sabina; pompano, Trachinotus caroli-
nus; pigfish, Orthopristis chrysoptera; sheepshead,
Archosargus probatocephalus; and black drum, Pogonias
cromis), or species with diets that include benthic inver-
tebrates and small fish (e.g., gray snapper, Lutjanus
griseus; southern flounder, Paralichthys lethostigma; gulf
flounder, P. albigutta).
The species with characteristically high levels of
total mercury were often upper-level piscivores or
omnivores (e.g., crevalle jack, Caranx hippos; Spanish
mackerel, Scomberomorus maculatus; ladyfish, Elops
saurus; and bluefish, Pomatomus saltatrix). Apex preda-
tors (e.g., king mackerel, S. cavalla; blacktip shark,
Carcharhinus limbatus; and bull shark, C. leucas) routinely
had high total mercury levels. Large king mackerel
from the gulf coast of Florida often contained mer-
cury levels greater than 0.5 ppm. Approximately 82%
of all king mackerel tested from Florida waters had total
mercury levels greater than or equal to 0.5 ppm, and
approximately 46% had total mercury levels greater
than or equal to 1.5 ppm.The majority of shark species
examined contained mean total mercury levels that
were greater than or equal to 0.5 ppm.These high lev-
els are likely related to the relatively slow growth,
longevity, and high trophic status of most of the shark
species tested in this study. Additionally, comparisons
between pregnant females and associated embryos
and neonate sharks from Florida waters indicated that
transmission of mercury from maternal sources to
embryo may be an important factor contributing to the
high levels of mercury in shark muscle tissue (Adams
and McMichael, 1999).
Although some of the upper-trophic level and off-
shore pelagic species examined in this study contained
comparatively high levels of total mercury, others did
not. Dolphin, Coryphaena hippurus, contained very low
mercury levels throughout Florida waters.The muscle
tissue of this fast-growing offshore pelagic species did
not accumulate high levels of mercury, and mean total
mercury levels for this species were among the lowest
observed in Florida marine fishes.The rapid growth rate
and comparatively short life span of dolphin may be
contributing factors to the low total mercury concen-
trations observed in this species.
Mercury levels for similar, coexisting fish species
from the same family were sometimes quite differ-
ent. For example, mercury levels in red drum, Sciaenops
ocellatus, were usually higher than those found in black
drum.This was especially apparent in the larger size-
classes. Large red drum often contained higher levels
than similar-size black drum. Low mercury levels were
usually found in black drum, even in very large spec-
imens (>1,000 mm SL).These differences may be related
to differences in the feeding ecology of the two species.
Black drum feed primarily on invertebrates (Simmons
and Breuer, 1962), whereas red drum, which also prey
on invertebrates, consume a greater proportion of fish
(Miles, 1950; Simmons and Breuer, 1962; Boothby and
Avault, 1971; Peters and McMichael, 1987; FWC-FMRI,
unpublished data). Although available data are limit-
ed, certain invertebrates may contain mercury levels
that are lower than those found in many fish species
(Gardner et al., 1975; Stickney et al., 1975; Jop et al.,
1997).
Similarly, mercury levels for species within the
same genus were sometimes divergent. Preliminary
results for mercury levels contained in yellowfin tuna,
Thunnus albacares, and blackfin tuna, Thunnus atlanti-
cus, collected from the same region were strikingly
different. Blackfin tuna from the offshore waters adja-
cent to the Indian River Lagoon system typically had
higher mercury levels than yellowfin tuna from these
waters. Although yellowfin tuna were larger (572–1,048
mm SL; mean = 813 mm SL) than blackfin tuna exam-
ined in this study (421–791 mm SL; mean = 686 mm SL),
the mean mercury level in yellowfin tuna (mean = 0.30
ppm) was lower than that detected in blackfin tuna
(mean = 1.16 ppm). Additional samples are currently
being collected by FWC-FMRI to further investigate the
mercury content differences between these closely
related, sympatric species.
A number of species had highly variable total mer-
cury levels. For example, total mercury levels for spotted
seatrout, Cynoscion nebulosus, varied greatly with fish
size and sampling area. In the Indian River Lagoon,
total mercury levels for females were not significant-
ly different from those for males; however, there was
a stronger relationship between total mercury level
and fish length for females than for males. Growth of
spotted seatrout in Florida is highly variable, and
females are typically larger at a particular age than
males (Murphy and Taylor, 1994), which may explain
some of the variation in total mercury levels observed.
The diverse diet of this species (Lassuy, 1983; Johnson
FMRI Technical Report TR-9 33
Mercury Levels in Marine and Estuarine Fishes of Florida 1989–2001 Adams et al.
and Seaman, 1986) may further explain the high vari-
ation in total mercury levels in spotted seatrout (Rider
and Adams, 2000).
A positive relationship between total mercury level
and fish length was observed for many species exam-
ined, indicating that mercury levels tend to increase as
individuals of some species grow. This is an important
consideration when retaining and consuming certain
marine and estuarine fishes. Mercury results from this
study directly support the current maximum size limit
for red drum within the State of Florida.The majority
of red drum containing high mercury levels were indi-
viduals larger than or near the maximum length of the
“slot limit”for this species. With the exception of one
smaller fish (527 mm SL), all red drum with total mer-
cury levels greater than or equal to 1.5 ppm were large
fish (mean = 791 mm SL) that would not be consumed
by humans because of Florida’s current size regulations.
Preliminary results indicate that regional differ-
ences in total mercury levels in muscle tissue of some
Florida fish species may exist. Mercury levels in sev-
eral species examined (e.g., bluefish, Pomatomus saltatrix;
Spanish mackerel, Scomberomorus maculatus; and com-
mon snook, Centropomus undecimalis) from both the
gulf coast and the Florida Keys/Florida Bay regions
were often higher than were mercury levels in fish of
the same species and size sampled from the Atlantic
coast of Florida.These large-scale regional differences
may be related to differences in available mercury
within these regions or other related factors. Because
mercury cycles through atmospheric, aquatic, and ter-
restrial components of the environment and is
deposited and made available from multiple sources,
it is difficult to effectively quantify available mercury
and correlate it with levels found within the muscle tis-
sue of marine and estuarine fishes.
Localized elevation of mercury concentrations in
freshwater and terrestrial organisms from specific
areas, waterbodies, or specific habitat types has been
detected in Florida (Lange et al., 1993; Sepulveda, 1999;
Rumbold et al., 2002). Preliminary analyses from this
study indicate that marine fish collected from specif-
ic, small-scale, localized areas can contain higher levels
of mercury than similar fish collected from other near-
by areas do. Elevated levels of mercury in spotted
seatrout collected within a small, localized area of
Florida Bay may influence the overall total mercury lev-
els reported for this species from the Florida
Keys/Florida Bay region. Within the distribution of
spotted seatrout from Florida Keys/Florida Bay, a group
was isolated that contained higher levels of mercury
than did other fish sampled from this area.The major-
ity of these “higher-level”fish were collected specifically
from the Deer Key area, located in northeastern Flori-
da Bay within the boundaries of the Everglades Nation-
al Park (latitude ~25°11.113′N; longitude ~80°32.202′W).
Although the historical movements and habitat use of
these fish are unknown, this illustrates how sample
groups containing elevated mercury levels collected
from specific sites can influence regional results.These
small-scale location effects potentially contribute to the
larger-scale regional differences observed for several
marine and estuarine fish species. Additional sam-
ples from this area and other areas in south Florida may
help clarify these possible linkages.
Results of this study indicate that mean total mer-
cury levels for the majority of species examined were
below the 0.5-ppm threshold level designated by DOH.
Data regarding other species (e.g., king mackerel, Span-
ish mackerel, bluefish, ladyfish, crevalle jack, great
barracuda, gafftopsail catfish, and blackfin tuna) sup-
port the current health advisories urging limited
consumption because of high mercury levels (HRS,
1991, 1995, 1996; DOH, 2000, 2003). Mercury levels in
Florida’s estuarine and marine fishes varied by species,
fish size, and sampling location. Sampling of fish for
mercury analysis is continuing, and future research
relating mercury levels to fish age, feeding ecology, and
trophic structure of Florida’s marine and estuarine
ecosystems will help us to further identify the causes
of these variations.
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FMRI Technical Report TR-9 49
Mercury Levels in Marine and Estuarine Fishes of Florida 1989–2001 Adams et al.
APPENDIX TABLE
Length and total mercury (Hg) data for marine and estuarine fishes collected from Florida waters from 1989 to 2001.
Lengths of bony fishes are presented as mm standard length (lengths of king mackerel are presented as mm fork length).
Lengths of shark species are presented as mm precaudal length, unless otherwise denoted. Lengths of ray species are pre-
sented as mm disk width. * = lengths are presented as mm total length. ** = lengths are presented as mm lower jaw total
length. All total mercury levels are reported as parts per million (ppm) wet weight. Min. = minimum, Max. = maximum,
Med. = median. IR = Indian River Lagoon and adjacent coastal waters; TB = Tampa Bay and adjacent coastal waters; CH
= Charlotte Harbor; KY = Florida Keys/Florida Bay; FW = Choctawhatchee Bay; SB = Sarasota Bay and adjacent coastal
waters; EV = Florida Everglades coastal waters; VC = Volusia County and adjacent coastal waters; TQ = Tequesta/south-
ern Indian River Lagoon and adjacent coastal waters; JX = northeast Florida and adjacent coastal waters; AP =
Apalachicola Bay and adjacent coastal waters.
Family Length (mm) Hg (ppm)
Species Common name Area n Mean Min. Max. Mean Med. Min. Max.
Odontaspididae
Odontaspis taurus Sand tiger shark IR 1 1,100* 1,100 1,100 0.30 0.30 0.30 0.30
Lamnidae
Carcharodon carcharius White shark CH 1 3,901* 3,901 3,901 5.40 5.40 5.40 5.40
IR 4 2,980* 2,270 4,191 5.42 4.80 2.10 10.00
KY 2 4,416* 3,962 4,870 4.30 4.30 2.60 6.00
Isurus oxyrinchus Shortfin mako KY 1 2,055* 2,055 2,055 3.20 3.20 3.20 3.20
Carcharhinidae
Carcharhinus acronotus Blacknose shark CH 1 490 490 490 0.35 0.35 0.35 0.35
IR 5 760 700 820 0.58 0.56 0.38 0.75
Carcharhinus brevipinna Spinner shark IR 9 844 659 1,000 0.61 0.63 0.31 0.97
Carcharhinus isodon Finetooth shark IR 1 470 470 470 0.20 0.20 0.20 0.20
Carcharhinus leucas Bull shark CH 3 742 680 850 0.97 1.20 0.42 1.30
IR 55 757 552 1,075 0.78 0.74 0.24 1.70
TB 1 665 665 665 0.66 0.66 0.66 0.66
Carcharhinus limbatus Blacktip shark CH 12 574 416 815 0.79 0.72 0.34 1.60
IR 25 818 223 1,510 0.76 0.63 0.16 2.30
KY 14 888 603 1,210 1.84 1.85 0.85 2.60
TB 47 559 405 975 0.54 0.47 0.03 1.60
Mustelus norrisi Florida smoothhound CH 1 495 495 495 1.20 1.20 1.20 1.20
Negaprion brevirostris Lemon shark CH 3 851 703 960 0.70 0.56 0.43 1.10
KY 2 882 610 1,155 0.65 0.65 0.61 0.70
TB 1 565 565 565 0.18 0.18 0.18 0.18
Rhizoprionodon terraenovae Atlantic sharpnose IR 81 592 220 857 1.06 0.95 0.11 2.30
shark VC 4 630 592 662 0.57 0.40 0.37 1.10
Sphyrnidae
Sphyrna lewini Scalloped hammerhead IR 6 379 279 654 0.44 0.45 0.33 0.54
TB 3 821 582 1,060 1.25 1.10 0.26 2.40
Sphyrna tiburo Bonnethead CH 17 422 263 690 0.34 0.27 0.04 0.96
FW 3 596 493 775 0.58 0.34 0.31 1.10
IR 137 481 206 1,081 0.39 0.24 0.08 1.50
KY 9 629 500 688 1.14 1.20 0.28 1.60
TB 47 616 288 800 0.59 0.52 0.03 1.60
Pristidae
Pristis pectinata Smalltooth sawfish TB 1 3,740 3,740 3,740 0.70 0.70 0.70 0.70
KY 1 398 398 398 0.19 0.19 0.19 0.19
50 FMRI Technical Report TR-9
Adams et al. Mercury Levels in Marine and Estuarine Fishes of Florida 1989–2001
Family Length (mm) Hg (ppm)
Species Common name Area n Mean Min. Max. Mean Med. Min. Max.
Dasyatidae
Dasyatis americana Southern stingray TB 3 454 410 480 0.17 0.18 0.14 0.19
Dasyatis sabina Atlantic stingray CH 9 254 188 310 0.25 0.20 0.12 0.45
FW 6 249 173 308 0.25 0.28 0.06 0.44
IR 35 204 329 94 0.16 0.16 0.01 0.44
JX 4 155 113 280 0.10 0.02 0.02 0.34
TB 4 248 213 280 0.33 0.31 0.17 0.54
Dasyatis say Bluntnose stingray CH 1 200 200 200 0.02 0.02 0.02 0.02
IR 7 273 150 383 0.07 0.08 0.02 0.14
KY 2 250 200 300 0.11 0.11 0.10 0.12
TB 14 390 254 540 0.20 0.17 0.06 0.59
Gymnura micrura Smooth butterfly ray IR 3 407 351 497 0.15 0.16 0.13 0.17
KY 1 393 393 393 0.11 0.11 0.11 0.11
VC 1 308 308 308 0.07 0.07 0.07 0.07
Myliobatidae
Myliobatis freminvillei Bullnose ray IR 1 377 377 377 0.12 0.12 0.12 0.12
Rhinoptera bonasus Cownose ray CH 2 424 363 485 0.06 0.06 0.03 0.09
TB 4 551 420 670 0.34 0.29 0.14 0.64
Acipenseridae
Acipenser brevirostrum Shortnose sturgeon VC 1 834* 834 834 0.12 0.12 0.12 0.12
Lepisosteidae
Lepisosteus platyrhincus Florida gar IR 1 435 435 435 0.09 0.09 0.09 0.09
Elopidae
Elops saurus Ladyfish AP 50 258 215 395 0.09 0.06 0.02 0.73
CH 35 317 240 495 0.34 0.23 0.08 1.60
CK 3 342 335 350 0.18 0.17 0.13 0.23
FW 6 357 295 420 0.53 0.53 0.34 0.69
IR 30 373 115 580 0.72 0.56 0.04 2.60
KY 16 322 235 425 0.36 0.31 0.07 0.99
TB 78 350 209 472 0.52 0.42 0.07 1.90
Megalops atlanticus Tarpon IR 20 523 211 685 0.18 0.17 0.03 0.47
KY 4 532 480 585 0.40 0.32 0.26 0.69
Albulidae
Albula vulpes Bonefish KY 13 584 485 656 0.53 0.45 0.23 1.10
CH 7 207 138 248 0.18 0.16 0.12 0.28
FW 4 196 175 214 0.10 0.09 0.06 0.16
Clupeidae
Brevoortia smithi Yellowfin menhaden IR 2 209 198 221 0.07 0.07 0.04 0.10
TB 2 244 218 270 0.16 0.16 0.16 0.16
Opisthonema oglinum Atlantic thread herring CH 4 151 137 157 0.19 0.18 0.14 0.24
FW 4 200 150 290 0.11 0.14 0.02 0.15
Harengula jaguana Scaled sardine CH 1 133 133 133 0.33 0.33 0.33 0.33
Synodontidae
Synodus foetens Inshore lizardfish IR 3 398 370 443 0.36 0.36 0.15 0.58
KY 1 212 212 212 0.09 0.09 0.09 0.09
Ariidae
Arius felis Hardhead catfish CH 7 296 278 325 0.22 0.16 0.09 0.39
FW 12 287 213 390 0.23 0.23 0.10 0.44
IR 13 284 210 352 0.15 0.12 0.02 0.34
TB 13 301 270 346 0.18 0.14 0.05 0.50
FMRI Technical Report TR-9 51
Mercury Levels in Marine and Estuarine Fishes of Florida 1989–2001 Adams et al.
Family Length (mm) Hg (ppm)
Species Common name Area n Mean Min. Max. Mean Med. Min. Max.
Bagre marinus Gafftopsail catfish CH 4 374 262 440 0.67 0.66 0.52 0.85
FW 4 487 470 501 0.96 0.98 0.88 1.00
IR 11 302 115 528 0.33 0.38 0.03 0.72
TB 59 374 211 492 0.60 0.54 0.02 1.80
Batrachoididae
Opsanus beta Gulf toadfish TB 6 220 200 244 0.17 0.19 0.06 0.25
Centropomidae
Centropomus undecimalis Snook CH 59 479 285 710 0.37 0.36 0.12 1.10
CK 1 700 700 700 0.19 0.19 0.19 0.19
EV 19 619 448 730 0.63 0.57 0.19 1.50
IR 76 454 262 745 0.22 0.21 0.06 0.42
KY 79 574 333 860 0.60 0.51 0.07 1.80
TB 84 484 168 867 0.39 0.34 0.03 1.40
TQ 106 418 301 625 0.22 0.21 0.06 0.48
Serranidae
Centropristis striata Black sea bass CH 1 202 202 202 0.17 0.17 0.17 0.17
TB 11 131 98 173 0.13 0.12 0.08 0.21
VC 9 226 205 245 0.14 0.14 0.12 0.17
Centropristis philadelphica Rock sea bass VC 1 125 125 125 0.07 0.07 0.07 0.07
Epinephelus itajara Goliath grouper TB 13 407 296 519 1.15 1.10 0.09 3.30
CH 10 1,320 1,090 1,660 0.13 0.03 0.01 0.58
EV 8 540 330 715 0.35 0.30 0.10 0.65
Epinephelus drummondhayi Speckled hind TB 7 422 290 713 0.20 0.15 0.12 0.34
Epinephelus flavolimbatus Yellowedge grouper IR 2 537 485 590 0.37 0.37 0.34 0.41
TB 8 316 273 353 0.23 0.22 0.13 0.34
Epinephelus morio Red grouper IR 3 418 338 534 0.34 0.30 0.28 0.43
KY 4 438 405 470 0.27 0.29 0.16 0.33
TB 39 428 382 533 0.33 0.32 0.11 0.66
VC 3 513 455 565 0.37 0.43 0.22 0.46
Epinephelus niveatus Snowy grouper IR 22 564 442 700 0.95 0.88 0.26 1.90
TB 5 472 300 763 0.26 0.20 0.10 0.57
VC 2 460 430 490 0.25 0.25 0.23 0.27
Mycteroperca microlepis Gag CH 3 293 190 355 0.16 0.14 0.13 0.22
CK 32 570 450 725 0.47 0.44 0.22 0.87
IR 12 540 174 835 0.38 0.33 0.13 1.00
KY 5 511 428 605 0.46 0.35 0.24 0.82
TB
38
378
137
783
0.30
0.21
0.04 1.06
VC 7 719 514 890 0.68 0.40 0.12 1.80
Mycteroperca bonaci Black grouper KY 8 772 636 1,000 1.16 1.15 0.83 1.60
TB 4 622 395 1,156 0.57 0.40 0.26 1.20
Mycteroperca phenax Scamp KY 1 495 495 495 0.45 0.45 0.45 0.45
TB 23 427 305 560 0.28 0.28 0.07 0.59
VC 5 531 378 610 0.35 0.37 0.14 0.45
Centrachidae
Lepomis macrochirus Bluegill TB 1 200 200 200 0.14 0.14 0.14 0.14
52 FMRI Technical Report TR-9
Adams et al. Mercury Levels in Marine and Estuarine Fishes of Florida 1989–2001
Family Length (mm) Hg (ppm)
Species Common name Area n Mean Min. Max. Mean Med. Min. Max.
Pomatomidae
Pomatomus saltatrix Bluefish CH 25 357 268 460 0.87 0.68 0.28 2.00
IR 149 346 239 731 0.44 0.36 0.11 1.50
JX 2 263 257 269 0.16 0.16 0.15 0.18
KY 11 366 235 405 0.87 0.60 0.36 1.60
TB 27 371 267 470 0.87 0.85 0.26 1.60
TQ 7 369 306 437 0.66 0.65 0.06 1.50
VC 5 592 103 783 0.61 0.72 0.10 0.86
Rachycenridae
Rachycentron canadum Cobia CH 3 775 665 890 0.60 0.69 0.27 0.83
IR 20 859 430 1,228 0.57 0.40 0.22 1.90
JX 3 1,036 840 1,342 1.42 1.50 0.75 2.00
KY 3 825 807 851 1.43 1.50 1.10 1.70
TB 11 631 362 1,000 0.47 0.34 0.13 1.30
TQ 2 948 876 1,020 0.41 0.41 0.33 0.50
VC 1 960 960 960 0.76 0.76 0.76 0.76
Carangidae
Caranx bartholomaei Yellow jack KY 1 450 450 450 0.41 0.41 0.41 0.41
Caranx hippos Crevalle jack CH 16 272 152 468 0.51 0.44 0.16 0.88
CK 16 258 158 355 0.28 0.30 0.08 0.75
IR 55 330 179 516 0.53 0.54 0.09 1.30
KY 55 365 225 575 0.97 0.76 0.02 3.90
TB 27 363 200 565 0.61 0.57 0.03 1.20
Caranx crysos Blue runner TB 1 207 207 207 0.18 0.18 0.18 0.18
Oligoplites saurus Leatherjacket FW 1 182 182 182 0.21 0.21 0.21 0.21
IR 2 227 219 235 1.45 1.45 1.20 1.70
Selene vomer Lookdown IR 16 178 135 241 0.20 0.14 0.07 0.98
Seriola dumerili Greater amberjack AP 1 987 987 987 0.91 0.91 0.91 0.91
FW 5 697 630 765 0.49 0.48 0.34 0.68
IR 7 816 535 940 0.59 0.49 0.35 0.96
JX 9 762 561 995 0.51 0.47 0.20 1.10
KY 4 790 594 890 0.66 0.62 0.40 0.99
VC 41 824 607 1,069 0.46 0.38 0.20 1.00
Seriola rivoliana Almaco jack VC 17 743 438 840 0.56 0.43 0.10 1.40
Seriola zonata Banded rudderfish VC 10 521 400 568 0.59 0.56 0.25 0.97
Trachinotus carolinus Florida pompano CH 13 306 193 395 0.18 0.18 0.06 0.28
IR 51 273 61 412 0.10 0.10 0.04 0.37
KY 4 295 203 371 0.15 0.11 0.03 0.35
TB 10 266 250 336 0.23 0.21 0.08 0.49
Trachinotus falcatus Permit CH 6 270 189 312 0.20 0.13 0.06 0.66
IR 18 277 55 887 0.22 0.08 0.06 1.60
KY 105 615 312 812 0.61 0.46 0.06 2.30
TB 34 267 155 360 0.15 0.11 0.02 0.51
Coryphaenidae
Coryphaena hippurus Dolphin AP 8 943 651 1,070 0.17 0.17 0.05 0.34
FW 1 837 837 837 0.06 0.06 0.06 0.06
IR 130 685 414 1,243 0.11 0.07 0.01 0.50
JX 2 877 876 879 0.22 0.22 0.20 0.25
KY 24 636 410 1,305 0.09 0.04 0.02 0.49
TQ 16 655 432 1,055 0.13 0.12 0.03 0.39
VC 24 657 452 890 0.12 0.13 0.02 0.30
FMRI Technical Report TR-9 53
Mercury Levels in Marine and Estuarine Fishes of Florida 1989–2001 Adams et al.
Family Length (mm) Hg (ppm)
Species Common name Area n Mean Min. Max. Mean Med. Min. Max.
Lutjandidae
Lutjanus griseus Gray snapper CH 35 218 158 290 0.13 0.13 0.06 0.32
IR 75 267 104 430 0.19 0.17 0.08 0.65
KY 140 246 152 396 0.21 0.19 0.03 0.62
TB 34 266 133 437 0.23 0.19 0.09 0.54
TQ 2 305 293 317 0.13 0.13 0.11 0.15
VC 15 369 218 505 0.17 0.15 0.10 0.27
Lutjanus analis Mutton snapper IR 5 169 144 220 0.11 0.11 0.09 0.13
KY 11 436 307 589 0.36 0.32 0.16 0.92
TQ 14 379 291 560 0.31 0.31 0.18 0.54
VC 2 347 320 375 0.28 0.28 0.25 0.31
Lutjanus campechanus Red snapper IR 1 552 552 552 2.80 2.80 2.80 2.80
VC 4 541 510 580 0.27 0.27 0.18 0.35
Lutjanus synagris Lane snapper IR 1 239 239 239 0.21 0.21 0.21 0.21
KY 4 212 189 244 0.34 0.33 0.27 0.43
TB 9 242 180 291 0.27 0.28 0.19 0.38
TQ 5 221 173 290 0.17 0.17 0.07 0.30
VC 2 281 273 290 0.25 0.25 0.19 0.31
Ocyurus chrysurus Yellowtail snapper KY 29 301 235 386 0.15 0.13 0.04 0.28
TQ 5 284 258 296 0.12 0.11 0.10 0.14
Rhomboplites aurorubens Vermilion snapper TB 1 226 226 226 0.25 0.25 0.25 0.25
VC 3 255 210 324 0.10 0.11 0.06 0.13
Lobotidae
Lobotes surinamensis Tripletail IR 74 430 270 620 0.13 0.11 0.01 0.61
KY 39 378 290 494 0.27 0.19 0.02 0.76
TB 1 270 396 396 0.07 0.07 0.07 0.07
Gerridae
Diapterus plumieri Striped mojarra CH 13 158 82 233 0.08 0.07 0.02 0.15
IR 5 190 151 242 0.12 0.13 0.01 0.25
TB 5 186 151 250 0.12 0.09 0.07 0.25
Diapterus auratus Irish pompano CH 3 250 242 264 0.18 0.18 0.12 0.25
Haemulidae
Haemulon plumieri White grunt CK 1 217 217 217 0.50 0.50 0.50 0.50
KY 15 177 138 213 0.23 0.19 0.09 0.51
TB 32 240 100 360 0.32 0.31 0.07 0.59
TQ 15 234 194 263 0.27 0.21 0.14 0.61
Haemulon sciurus Bluestriped grunt KY 3 186 170 212 0.28 0.38 0.06 0.40
Orthopristis chrysoptera Pigfish CH 11 189 156 210 0.20 0.13 0.04 0.66
FW 1 168 168 168 0.26 0.26 0.26 0.26
IR 21 198 143 260 0.14 0.12 0.02 0.41
KY 11 170 143 202 0.12 0.12 0.02 0.20
TB 7 198 170 219 0.19 0.16 0.13 0.30
VC 1 107 107 107 0.07 0.07 0.07 0.07
Sparidae
Archosargus probatocephalus Sheepshead AP 28 371 271 440 0.17 0.17 0.06 0.40
CH 17 278 170 365 0.21 0.16 0.08 0.66
CK 62 340 225 470 0.24 0.21 0.06 1.10
FW 4 233 185 300 0.16 0.14 0.08 0.27
IR 14 326 183 437 0.16 0.13 0.07 0.45
KY 25 249 133 429 0.19 0.13 0.06 0.52
TB 27 286 215 429 0.15 0.13 0.07 0.43
54 FMRI Technical Report TR-9
Adams et al. Mercury Levels in Marine and Estuarine Fishes of Florida 1989–2001
Family Length (mm) Hg (ppm)
Species Common name Area n Mean Min. Max. Mean Med. Min. Max.
Archosargus rhomboidalis Sea bream KY 1 161 161 161 0.18 0.18 0.18 0.18
Lagodon rhomboides Pinfish CH 5 158 103 224 0.15 0.17 0.13 0.17
IR 3 269 260 282 0.34 0.27 0.19 0.55
KY 3 141 128 149 0.06 0.06 0.05 0.07
Sciaenidae
Bairdiella chrysoura Silver perch CH 4 152 141 163 0.29 0.27 0.20 0.42
FW 8 139 128 151 0.35 0.41 0.02 0.49
IR 12 118 105 155 0.46 0.42 0.21 1.10
KY 9 146 135 172 0.24 0.20 0.15 0.46
TB 2 156 155 158 0.35 0.35 0.27 0.43
Cynoscion arenarius Sand seatrout CH 12 283 205 337 0.81 0.80 0.45 1.20
CK 15 266 224 301 0.34 0.32 0.25 0.46
TB 77 224 145 333 0.46 0.44 0.11 1.10
Cynoscion nebulosus Spotted seatrout AP 42 419 309 570 0.33 0.28 0.08 0.79
CH 56 359 160 545 0.42 0.33 0.14 1.50
CK 145 374 230 540 0.45 0.34 0.08 1.30
EV 8 354 265 425 0.43 0.34 0.18 0.71
FW 102 385 187 529 0.40 0.39 0.11 0.88
IR 215 394 143 680 0.47 0.41 0.02 1.70
JX 5 329 305 375 0.16 0.17 0.10 0.18
KY 76 324 152 460 0.64 0.43 0.02 2.50
TB 137 333 162 625 0.40 0.34 0.04 1.00
Cynoscion nothus Silver seatrout IR 16 195 171 230 0.24 0.24 0.09 0.39
TB 1 258 258 258 0.47 0.47 0.47 0.47
Cynoscion regalis/arenarius Species complex IR 64 251 159 369 0.29 0.22 0.08 0.84
JX 108 238 116 415 0.13 0.12 0.02 0.39
VC 2 167 165 170 0.11 0.11 0.11 0.12
Leiostomus xanthurus Spot CH 4 193 185 201 0.14 0.14 0.09 0.18
FW 12 123 101 161 0.16 0.14 0.03 0.46
IR 21 213 118 313 0.12 0.11 0.02 0.36
JX 9 146 125 164 0.04 0.04 0.02 0.07
SB 6 201 165 220 0.08 0.08 0.04 0.12
TB 19 184 163 211 0.11 0.11 0.03 0.25
Menticirrhus americanus Southern kingfish AP 1 295 295 295 0.33 0.33 0.33 0.33
CH 7 262 216 300 0.37 0.36 0.17 0.50
CK 6 259 238 273 0.13 0.12 0.08 0.20
IR 18 202 147 289 0.08 0.07 0.02 0.24
JX 19 193 121 238 0.13 0.10 0.02 0.78
TB 25 279 229 348 0.19 0.16 0.04 0.75
Menticirrhus saxatilis Northern kingfish AP 1 300 300 300 0.21 0.21 0.21 0.21
TB 3 237 221 265 0.29 0.24 0.15 0.48
Micropogonias undulatus Atlantic croaker CK 1 237 237 237 0.05 0.05 0.05 0.05
IR 21 217 89 385 0.06 0.04 0.02 0.18
JX 23 148 122 172 0.06 0.05 0.02 0.15
TB 2 275 250 300 0.08 0.08 0.07 0.08
Pogonias cromis Black drum CH 2 288 287 289 0.08 0.08 0.06 0.09
CK 1 430 430 430 0.18 0.18 0.18 0.18
EV 5 373 330 410 0.13 0.12 0.05 0.22
IR 36 588 243 1,049 0.14 0.13 0.02 0.65
KY 4 407 378 430 0.10 0.11 0.02 0.18
TB 23 470 193 850 0.24 0.21 0.01 0.49
FMRI Technical Report TR-9 55
Mercury Levels in Marine and Estuarine Fishes of Florida 1989–2001 Adams et al.
Family Length (mm) Hg (ppm)
Species Common name Area n Mean Min. Max. Mean Med. Min. Max.
Sciaenops ocellatus Red drum AP 82 451 358 618 0.20 0.20 0.06 0.69
CH 28 518 279 702 0.31 0.24 0.05 0.87
CK 133 398 223 606 0.18 0.18 0.06 0.55
EV 15 385 273 560 0.26 0.25 0.15 0.40
FW 15 408 180 621 0.17 0.13 0.05 0.35
IR 129 506 246 1,070 0.37 0.18 0.02 2.20
KY 45 455 230 628 0.48 0.35 0.10 2.70
TB 235 660 200 992 1.10 0.98 0.07 3.60
Umbrina coroides Sand drum KY 5 183 173 201 0.06 0.06 0.04 0.07
Ephippidae
Chaetodipterus faber Atlantic spadefish CH 5 226 190 253 0.33 0.29 0.24 0.45
IR 1 232 232 232 0.26 0.26 0.26 0.26
TB 2 226 225 227 0.34 0.34 0.21 0.47
IR 1 165 165 165 0.02 0.02 0.02 0.02
Mugilidae
Mugil cephalus Striped mullet CH 7 333 258 444 0.06 0.02 0.02 0.25
CK 15 276 205 339 0.02 0.02 0.02 0.02
FW 4 255 176 290 0.12 0.11 0.02 0.23
IR 14 302 237 469 0.06 0.04 0.02 0.24
KY 3 282 272 290 0.02 0.02 0.02 0.03
TB 28 304 155 443 0.08 0.04 0.01 0.78
Mugil curema White mullet CH 11 259 248 271 0.03 0.03 0.02 0.05
CK 2 205 200 210 0.02 0.02 0.02 0.02
FW 2 143 128 158 0.11 0.11 0.05 0.17
KY 15 250 181 290 0.05 0.02 0.02 0.25
TB 3 236 205 265 0.03 0.03 0.02 0.04
Mugil gyrans Fantail mullet CH 9 201 160 263 0.03 0.02 0.02 0.04
TB 3 250 240 260 0.04 0.04 0.04 0.04
Sphyraenidae
Sphyraena barracuda Great barracuda CH 1 237 237 237 0.36 0.36 0.36 0.36
IR 19 358 213 488 0.16 0.16 0.08 0.35
KY 62 628 119 1,096 0.87 0.72 0.08 3.10
TQ 3 612 602 622 0.54 0.55 0.44 0.63
Labridae
Lachnolaimus maximus Hogfish KY 19 289 200 341 0.16 0.14 0.08 0.35
Scombridae
Acanthocybium solanderi Wahoo AP 16 1,030 931 1,229 0.26 0.17 0.06 1.30
FW 7 1,146 1,052 1,291 0.68 0.62 0.27 1.40
IR 30 1,053 845 1,338 0.27 0.23 0.06 0.87
JX 1 1,119 1,119 1119 0.36 0.36 0.36 0.36
TQ 4 1,112 1,050 1,235 0.16 0.11 0.04 0.36
VC 3 1,092 1,012 1,235 0.39 0.39 0.29 0.50
Euthynnus alletteratus Little tunny IR 2 616 605 628 2.15 2.15 1.50 2.80
TB 9 527 458 582 0.40 0.39 0.16 0.69
TQ 2 527 465 590 0.63 0.63 0.29 0.98
VC 6 572 517 660 0.79 0.72 0.55 1.20
Scomberomorus cavalla King mackerel IR 16 787 648 1,280 0.55 0.33 0.19 2.50
JX 3 958 928 1,002 0.74 0.44 0.39 1.40
KY 2 1,311 1,245 1,378 1.70 1.70 1.30 2.10
SB 19 1,125 1,000 1,310 2.08 1.80 1.20 3.80
TB 98 1,045 620 1,330 1.56 1.35 0.25 4.00
VC 4 747 685 850 0.29 0.24 0.23 0.45
56 FMRI Technical Report TR-9
Adams et al. Mercury Levels in Marine and Estuarine Fishes of Florida 1989–2001
Family Length (mm) Hg (ppm)
Species Common name Area n Mean Min. Max. Mean Med. Min. Max.
Scomberomorus maculatus Spanish mackerel AP 6 345 242 445 0.35 0.29 0.10 0.79
CH 50 401 267 640 0.71 0.62 0.14 3.00
CK 1 330 330 330 0.32 0.32 0.32 0.32
FW 6 367 290 439 0.39 0.36 0.09 0.79
IR 98 359 178 715 0.32 0.25 0.06 1.30
JX 2 240 235 245 0.08 0.08 0.07 0.08
KY 3 377 255 440 0.69 0.68 0.46 0.93
SB 15 184 132 210 0.18 0.18 0.12 0.23
TB 187 345 188 569 0.53 0.47 0.10 2.90
TQ 20 482 383 618 0.39 0.38 0.22 0.58
VC 1 343 343 343 0.23 0.23 0.23 0.23
Scomberomorus regalis Cero TQ 1 279 279 279 0.15 0.15 0.15 0.15
Thunnus albacares Yellowfin tuna IR 33 813 572 1,048 0.30 0.31 0.15 0.65
Thunnus atlanticus Blackfin tuna IR 22 686 421 791 1.16 1.20 0.16 2.00
Istiophoridae
Istiophorus platypterus Sailfish TQ 1 1,800* 1,800 1,800 0.11 0.11 0.11 0.11
Makaira nigricans Blue marlin KY 8 2,254 2,080 2,565 3.08 2.75 0.98 6.80
Tetrapturus albidus White marlin IR 1 1,831** 1,831 1,831 0.27 0.27 0.27 0.27
KY 1 1,545** 1,545 1,545 0.31 0.31 0.31 0.31
Bothidae
Paralichthys dentatus Summer flounder JX 3 170 153 182 0.04 0.04 0.04 0.04
Paralichthys albigutta Gulf flounder AP 5 272 220 341 0.13 0.10 0.07 0.29
CH 70 295 116 456 0.31 0.28 0.06 1.10
CK 1 260 260 260 0.10 0.10 0.10 0.10
FW 18 290 204 448 0.20 0.20 0.08 0.35
IR 8 302 176 412 0.38 0.41 0.10 0.58
JX 1 145 145 145 0.02 0.02 0.02 0.02
KY 5 281 235 336 0.08 0.09 0.05 0.11
TB 65 275 172 412 0.20 0.16 0.01 0.60
TQ 2 485 471 500 0.39 0.39 0.32 0.46
VC 15 220 115 340 0.14 0.11 0.04 0.35
Paralichthys albigutta Southern flounder AP 6 338 275 410 0.16 0.12 0.07 0.30
FW 3 347 275 423 0.17 0.19 0.13 0.20
IR 23 340 162 576 0.18 0.13 0.07 0.50
JX 18 273 137 395 0.08 0.07 0.04 0.25
VC 17 245 175 320 0.11 0.10 0.06 0.21
Balistidae
Balistes capriscus Gray triggerfish VC 3 268 250 287 0.13 0.15 0.06 0.17
Molidae
Mola mola Ocean sunfish IR 1 1,740* 1,740 1,740 0.02 0.02 0.02 0.02
FMRI Technical Report TR-9 57
Florida Marine Research Institute
Technical Report Series
TR-1 Scarring of Florida’s Seagrasses: Assessment and Management Options. 1995.
TR-2 Understanding, Assessing, and Resolving Light-Pollution Problems on Sea Turtle Nesting
Beaches. Second Edition, Revised. 2000.
TR-2 Entendiendo, evaluando y solucionando los problemas de contaminación de luz en playas de
anidamiento de tortugas marinas. Florida Marine Research Institute Technical Report TR-2, tra-
ducción de la Tercera Edición inglesa, revisada. (In Spanish.) 2003.
TR-3 Checklists of Selected Shallow-Water Marine Invertebrates of Florida. 1998.
TR-4 Benthic Habitats of the Florida Keys. 2000.
TR-5 Florida’s Shad and River Herrings (Alosa Species): A Review of Population and Fishery Char-
acteristics. 2000.
TR-6 Mercury Levels in Marine and Estuarine Fishes of Florida. 2001.
TR-7 Movements of Radio-Tagged Manatees in Tampa Bay and Along Florida’s West Coast,
1991–1996. 2001.
TR-8 State of Florida Conservation Plan for Gulf Sturgeon (Acipenser oxyrinchus desotoi). 2001.
TR-9 Mercury Levels in Marine and Estuarine Fishes of Florida 1989–2001. Second Edition,
Revised. 2003.
58
