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Estimating the Benefits of Derelict Crab Trap Removal in the Gulf of Mexico

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Ghost fishing in derelict blue crab traps is ubiquitous and causes incidental mortality which can be reduced by trap removal programs. In an effort to scale the benefits of such removal programs, in the context of restoring the Gulf of Mexico after the Deepwater Horizon oil spill, this paper calculates the ecological benefits of trap removal by estimating the extent of derelict blue crab traps across Gulf of Mexico waterbodies and combining these estimates with Gulf-specific crab and finfish mortality rates due to ghost fishing. The highest numbers and densities of traps are found in Louisiana, with estimates ranging up to 203,000 derelict traps across the state and up to 41 traps per square kilometer in areas such as Terrebonne Bay. Mortality rates are estimated at 26 crabs per trap per year and 8 fish per trap per year. The results of this analysis indicate a Gulf-wide removal program targeting 10% of derelict traps over the course of 5 years would lead to a combined benefit of more than 691,000 kg of crabs and fish prevented from mortality in ghost fishing traps. These results emphasize the importance of ongoing derelict trap removal programs. Future work could assess additional benefits of trap removal programs, such as fewer entanglements of marine organisms, improved esthetics, and increases in harvestable catch. Lastly, this model could be utilized by fishery managers to calculate the benefits of other management options designed to decrease the extent and impact of derelict fishing gear.
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SPECIAL SECTION: RESTORATION BENEFITS IN GULF OF MEXICO
Estimating the Benefits of Derelict Crab Trap Removal
in the Gulf of Mexico
Courtney Arthur
1
&Scott Friedman
1
&Jennifer Weaver
2
&Dan Van Nostrand
3
&James Reinhardt
4
Received: 29 November 2019 /Revised: 21 July 2020 /Accepted: 29 July 2020
#The Author(s) 2020
Abstract
Ghost fishing in derelict blue crab traps is ubiquitous and causes incidental mortality which can be reduced by trap
removal programs. In an effort to scale the benefits of such removal programs, in the context of restoring the Gulf of Mexico
after the Deepwater Horizon oil spill, this paper calculates the ecological benefits of trap removal by estimating the extent of
derelict blue crab traps across Gulf of Mexico waterbodies and combining these estimates with Gulf-specific crab and finfish
mortality rates due to ghost fishing. The highest numbers and densities of traps are found in Louisiana, with estimates ranging up
to 203,000 derelict traps across the state and up to 41 traps per square kilometer in areas such as Terrebonne Bay. Mortality rates
are estimated at 26 crabs per trap per year and 8 fish per trap per year. The results of this analysis indicate a Gulf-wide removal
program targeting 10% of derelict traps over the course of 5 years would lead to a combined benefit of more than 691,000 kg of
crabs and fish prevented from mortality in ghost fishing traps. These results emphasize the importance of ongoing derelict trap
removal programs. Future work could assess additional benefits of trap removal programs, such as fewer entanglements of
marine organisms, improved esthetics, and increases in harvestable catch. Lastly, this model could be utilized by fishery
managers to calculate the benefits of other management options designed to decrease the extent and impact of derelict fishing
gear.
Keywords Marine debris .Crab traps .Ghost fishing .Ecological restoration
Introduction
Marine debris, defined as any persistent solid material that is
manufactured or processed and directly or indirectly, inten-
tionally or unintentionally, disposed of or abandoned in the
marine environment or Great Lakes(33U.S.C. 1951 et seq.,
as amended), is widespread in marine and coastal environ-
ments. The effects of marine debris on wildlife have been
documented for decades (CBD 2012). For example, organ-
isms become trapped or entangled in derelict fishing gear or
ingest smaller debris fragments and particles, resulting in re-
duced health and mortality (e.g., Chiappone et al. 2002;
MacFadyen et al. 2009; Wilcox et al. 2016). Furthermore,
marine debris can scar seagrass habitats and coral reefs, en-
tangle boat engines and fishing gear, and impact beach es-
thetics (National Oceanic and Atmospheric Administration
(NOAA) 2008). Restoration projects that remove marine de-
bris, derelict fishing gear in particular, reduce incidental mor-
tality in gear and restore coastal habitats.
One of the most persistent and damaging types of marine
debris is derelict fishing gear because it physically impacts
habitats, entangles larger organisms, and continues to catch
fish and invertebrates in a process known as ghost fishing
(Butler and Matthews 2015; MacFadyen et al. 2009; Scheld
et al. 2016). Gear that is capable of ghost fishing may capture
target and non-target species and be a cause of mortality to
those species, because, once lost, the gear is no longer re-
trieved regularly by fishers. Derelict fishing gear includes gill
nets,trawlnets,longlines,andtraps.Trapfisheriesare
Communicated by Mark S. Peterson
Electronic supplementary material The online version of this article
(https://doi.org/10.1007/s12237-020-00812-2) contains supplementary
material, which is available to authorized users.
*Courtney Arthur
carthur@indecon.com
1
Industrial Economics, Inc., Cambridge, MA 02140, USA
2
Research Planning, Inc., Columbia, SC 29201, USA
3
NOAA Restoration Center, Mobile, AL 36608, USA
4
NOAA Restoration Center, Silver Spring, MD 20910, USA
https://doi.org/10.1007/s12237-020-00812-2
/ Published online: 6 August 2020
Estuaries and Coasts (2020) 43:1821–1835
especially susceptible to gear loss because they span large
areas, require high densities of gear to remain productive,
and are not continuously monitored (Breen 1990). Causes of
trap loss include storms, currents, siltation, deterioration, van-
dalism, abandonment, and buoy lines severed by vessels in
transit (Clark et al. 2012;Guilloryetal.2001b; Lewis et al.
2009; Shively 1997; Uhrin and Fonseca 2005). For example,
success in blue crab (Callinectes sapidus) fisheries depends on
fishers deploying a high number of traps over a large area and
continuously replacing lost traps, creating the potential for
high densities of derelict traps. Trap loss rates are difficult to
estimate (personal communication, LA Sea Grant), in part
because many traps are unmarked and fishers infrequently
report the number of traps fished as well as trap losses.
Abandoned traps are hypothesized to be a source of derelict
traps due to temporary fishers leaving the fishery (Guillory
et al. 2001b). Preliminary estimates of annual trap loss rates
range from 20 to 100% of the total traps fished (GSMFC
2015). The high estimate of 100% is considered a result of
intentional abandonment by fishers in advance of major storm
systems or to avoid paying disposal fees (Guillory et al.
2001b).
In addition to being susceptible to loss, traps are designed
to withstand harsh conditions for extended periods of time and
thus continue to capture and kill fish and invertebrates (Arthur
et al. 2014; Butler and Matthews 2015; MacFadyen et al.
2009). Blue crab traps, such as those used in the Gulf of
Mexico and Chesapeake Bay, are made of galvanized metal
or vinyl-coated wire, which is more effective at withstanding
the corrosive nature of high salinity environments (Carr and
Harris 1997;Guilloryetal.2001a). The degradation time of
abandoned traps is estimated to be greater than 2 years
(Giordano et al. 2010; Guillory et al. 2001b;Shively1997;
Stanhope et al. 2011). As such, derelict traps may continue to
ghost fish for more than 1 year after loss or abandonment, and
in Louisiana, the life expectancy has been estimated at 3 years
(LDFW and LA Sea Grant, personal communication; Shively
1997;Vossetal.2011).
The prevalence of ghost fishing and damage to benthic
habitats, together with high rates of trap loss and longevity
of trap function, leads to a perfect storm that makes derelict
fishing traps one of the most damaging types of marine debris.
Derelict traps can continue to catch and kill biota, even after
the bait has disintegrated or been eaten, and may be a signif-
icant source of unaccounted blue crab and finfish mortality
(Arthur et al. 2014;Guilloryetal.2001b). However, the im-
pacts of derelict fishing traps can be prevented through robust
programs to find and remove them from impacted
waterbodies. Trap removal programs are a promising ecolog-
ical restoration approach with a suite of benefits, such as re-
duction of the number of fish and invertebrates killed annually
due to ghost fishing, reduction of entanglement hazards for
wildlife and boaters, increased esthetics, reduction of habitat
impacts such as smothering seagrasses or coral reefs, and po-
tentially increases harvestable catch (see, e.g., Arthur et al.
2014;Scheldetal.2016; Matthews and Uhrin 2009).
Estuarine crabs and fishes injured due to the Deepwater
Horizon oil spill may benefit from restoration projects that
remove derelict traps in the Gulf of Mexico, and funding for
removal programs may be available as part of ongoing resto-
ration efforts (DOJ 2016; Trustees 2016). Here, we build upon
published data, state-based fishery surveys, and natural re-
source management approaches to quantify the benefits of
removing derelict blue crab traps in the Gulf of Mexico. We
utilize the concepts of resource equivalency analysis (REA), a
scaling method often employed in natural resource damage
assessment that uses biological metrics as the unit of measure
(e.g., number of organisms or lost biomass). As Baker et al.
(2020) describe, through REA natural resource injuries and
the estimated restoration benefits needed to replace what
was lost are easily replicated through use of transparent pa-
rameters and a stepwise replacement model. Here, the model
parameters estimate the restoration benefit of a derelict trap
removal project. We report restoration benefits in units of crab
and finfish biomass not killed due to ghost fishing per
waterbody per year, in order to allow resource managers to
compare proposed removal efforts in a common currency.
Methods
The analysis presented in this paper estimates the avoided
mortality expected from the removal of derelict fishing traps
(i.e., the biomass of fish and invertebrates not killed in traps
that are removed), based on the number of derelict traps per
waterbody, the mortality rate per derelict trap, and the scale of
the removal program. In addition, the analysis accounts for the
gain in the number of organisms in the previous year (i.e., it is
assumed that benefits accrue for 2 years, or the assumed du-
ration over which traps may continue to ghost fish, except in
Texas and Florida due to regulations for biodegradable com-
ponents), the percent of traps that are ghost fishing, and the
average crab and fish biomass. The derivation of each of these
analytical parameters is described in the following sections.
Derelict Traps per Waterbody
The number of derelict crabtraps in the fishery is a function of
the number of traps deployed each year and the rate at which
traps are lost. The number of traps deployed each year is
dependent on the number of commercial and recreational fish-
ers and their effort.
This analysis relied on state licensure data, estimates of
inactive licenses (i.e., latentlicenses), and state-specific reg-
ulatory limits on the number of traps allowed per license to
estimate the number of commercial fishers and the
1822 Estuaries and Coasts (2020) 43:1821–1835
corresponding number of traps in each state. The number of
commercial licenses was obtained from Texas, Louisiana,
Mississippi, and Alabama for years 20022013 and from
Florida for years 20092013. As reported in the Louisiana
blue crab fishery management plan, the number of license
holders that report landings is approximately half of the total
number of license holders (Bourgeois et al. 2014). To the best
of our knowledge, estimates of the magnitude of
underreported landings in the GoM for the blue crab fishery
are not available. However, in the most recent blue crab stock
assessment, VanderKooy (2013) considered the magnitude of
underreporting to be small because the bulk of the fishery
consists of large-scale entities that would be detected if
underreporting occurred, and included a parameter estimating
catch measurement error at 5%. Thus, in Louisiana, this anal-
ysis adjusted the estimate of commercial fishers to reflect ac-
tive license holders plus a percentage of total license holders
that may fish but do not officially report landings (5%). The
assumption of 5% may underestimate the total underreporting
for the region. Similar information was presented in the most
recent Gulf of Mexico blue crab management plan (GSMFC
2015), and this analysis assumed 50% of license holders in
Texas, Mississippi, Alabama, and Florida do not participate in
the blue crab fishery each year.
Each type of commercial license is permitted to fish a cer-
tain number of blue crab traps (Table 1). In Florida, the aver-
age number of traps per license was determined by weighting
the number of each license type sold within the state by the
number of traps permitted by that license, and then determin-
ing a weighted average. Alabama, Mississippi, and Louisiana
do not limit the number of traps used by commercial fishers.
Therefore, we utilized responses to a survey of commercial
fishers in Louisiana, conducted by Louisiana Sea Grant to
estimate the number of traps used by Louisiana fishers (per-
sonal communication, Dr. J. Anderson Lively, LA Sea Grant).
In the absence of survey data or information on the level of
fishing effort in Alabama and Mississippi, we applied the
average number of traps used per fisher in Louisiana to
Alabama and Mississippi. We calculate the number of com-
mercial traps in each state per year by estimating the number
of license holders (reduced by 50% to account for latent
licenses) then multiplying by the number of traps permitted
per license.
Commercial TrapsC;T¼LicenseC;T0:50 Traps
LicenseC
C= commercial blue crab fishery per state; T=year
The recreational fishing sector is also a source of derelict
traps. However, the level of information that states collect on
the number of recreational blue crab traps is uneven
(VanderKooy 2013). Recreational licensure data for
Louisiana and Mississippi were obtained from state fishery
managers for years 20022013 and are used in this analysis.
According to state regulations, each recreational license hold-
er is permitted 10 traps in Louisiana and 6 traps in Mississippi.
Recreational traps were estimated by multiplying the number
of recreational blue crab fishing licenses by the number of
traps permitted per license in Louisiana and Mississippi.
Recreational TrapsR;TLA;MSðÞ
¼LicenseR;T

Traps
LicenseR
R= recreational blue crab fishery per state; T=year
Recreational license data were not available from Texas,
Alabama, and Florida. Based on the most recent blue crab
stock assessment in the GoM, the recreational effort in
Texas, Alabama, and Florida was assumed to be 5% of com-
mercial effort (e.g., recreational traps are estimated as 5% of
commercial traps in Texas, Alabama, and Florida;
VanderKooy 2013).
Recreational TrapsR;TFL;AL;TXðÞ¼5%ðÞTrapsC;T

R= recreational blue crab fishery per state; T=year; C=
commercial blue crab fishery per state
Commercial and recreational traps were summed per
state per year. Parameters are summarized in Table 1.
The spatial distribution of derelict traps is calculated as a
number of derelict traps per waterbody. Juvenile and adult
crabs use a wide range of estuarine habitat from freshwa-
ter to fully saline conditions and are primarily fished in
large shallow and intertidal areas at depths less than 20 m
(Anderson 2014). Thus, it was assumed that the majority
of each estuarine waterbody, including mud and vegetated
benthos, represent potential crab habitat (GSMFC 2015;
VanderKooy 2013). Waterbodies were chosen by identify-
ing locations that had reported blue crab landings for mul-
tiple years. Landings per waterbody were compared with
state-wide landings to develop a proportional fishing effort
for each waterbody in each year with available data.
Louisiana, Alabama, and Mississippi had sufficient data
to interpret landings from 2002 to 2013. Texas had land-
ings data available from 2007 to 2013. Florida had license
data available at the waterbody level from 2009 to 2013
and this analysis used those data to estimate a number of
blue crab traps used in Florida waterbodies.
EffortW;T¼LandingsW;T

LandingsS;T

W= waterbody level, T=year,S=statelevel
The proportional fishing effort was used to apportion the
total number of traps (derived at the state level) to the 28
waterbodies for each year with available data. Data were av-
eraged across years, and the average number of traps per
1823Estuaries and Coasts (2020) 43:1821–1835
waterbody was used in subsequent analyses. In the absence of
additional information, this approach inherently assumes that
trap efficiency and catchability do not vary across
waterbodies, and may underestimate the number of traps used
in some waterbodies with smaller landings estimates.
TrapsW;T¼EffortW;T

TrapsCþR

Annual TrapsW¼TrapsW;T

n
W= waterbody level, T=year, C=commercial traps, R=
recreational traps, n=numberof years
Numbers of derelict traps were estimated by multiplying a
trap loss rate, informed by a literature review, by the number
of traps per waterbody. Based on information in white papers
and published literature, the rate at which blue crab traps are
lost was assumed to be 25% of traps used in the fishery
(Guillory et al. 2001b). To compare numbers of traps across
waterbodies of varying sizes, trap density was calculated
using the number of derelict traps per waterbody and the esti-
mated available blue crab habitat (i.e., mud and vegetated
benthos) in each waterbody. As a general rule, we assigned
waterbodies that spanned multiple states to the state that re-
ported landings for that particular waterbody. To estimate the
available blue crab habitat per waterbody, we used ESRI geo-
graphical information system (GIS) software to subtract nav-
igation channels from the available habitat (generally, the
estuary bounds as delineated by Nelson and U.S. DOC
2015) to account for regulations that prohibit setting traps
within navigable waterways.
Derelict TrapsW¼TrapsWLoss Rate
AreaW
W= waterbody level
This analysis resulted in an estimate of the density of der-
elict traps (in traps per square kilometer) in each of the 28
waterbodies. The data were imported into GIS to create maps
that delineate the extent of each waterbody and the density of
derelict traps.
Mortality in Derelict Traps
We estimated the number of organisms (crab and fish) killed
per derelict trap per year by reviewing available data from in
situ studies of capture and mortality rates in crab traps (e.g.,
Antonelis et al. 2011; Bilkovic et al. 2014; Bilkovic et al.
2016; Butler and Matthews 2015;Havensetal.2008).
While per-trap estimates of the number of crabs killed were
directly available, per-trap estimates of finfish killed were not
available. As such, for finfish, we estimated a number per trap
killed as a function of an estimated catch rate and an assumed
mortality rate.
Table 1 Parameters used to estimate the number of derelict traps in 28 Gulf of Mexico waterbodies
Parameter (units) Source Value
TX LA MS AL FL
Commercial licenses
a
State Agencies 214 2240 203 201 200
Recreational licenses
b
State Agencies 5115 485 ––
Number of permitted commercial traps
c
State Legislation 200 No limit No limit No limit Varies by License
Number of permitted recreational traps
b
State Legislation 6 10 6 5 5
Latency (%)
d
Literature (GSMFC 2015)50
Commercial landings per waterbody (lbs.) State Agencies Varies By Waterbody See Supplementary Material
Rate of trap loss (%) Literature (Guillory et al. 2001b)25
Area of waterbody (km
2
) NODC, Census Varies See Supplementary Material
a
The estimates of commercial licenses are averages using multiple years of available licensure data. In Florida, this includes only the fishing commu-
nities reporting landings north of Tampa to the state border with Alabama. In Louisiana, we use the number of licenses reporting sales and add an estimate
of the number of non-reporting fishers (5%)
b
Recreational licensure data were unavailable in Texas, Alabama, and Florida. For those states, we estimate the number of recreational licenses and the
number of permitted traps by assuming recreational fishing represents 5% of the commercial fishery, the same approach taken in the recent blue crab
stock assessment (Vanderkooy 2013)
c
The number of traps permitted by a commercial license is regulated in Texas and Florida. In Florida, the limits vary by the type of commercial trap, and
we determined a weighted average based type of license and its regulation (n= 535). In cases where the state does not impose a limit on the number of
traps utilized, we determined an average number of traps reported by commercial fishers in a survey conducted by Louisiana Sea Grant (n=369)and
applied this average to LA, MS, and AL waterbodies
d
Latency, as described here, refers to the number of non-reporting and non-participating fishers. We estimate that 50% commercial licenses are latent,
after GSMFC (2015)
1824 Estuaries and Coasts (2020) 43:1821–1835
Crab Mortality
Guillory (1993) reported the number of crabs killed per trap;
thus, there is no need to utilize capture rates to estimate the
number killed per trap. Our analysis assumed the crab mortal-
ity rate from Guillory (1993), 55% (equivalent to 25.8 crabs
per trap per year), reflects conditions across the GoM, and
used this rate in subsequent analyses for all 28 GoM
waterbodies. Mortality rates were converted to biomass by
multiplying the number killed by the average weight of a blue
crab (VanderKooy 2013;Westetal.2016). Average crab
weight was based on the average carapace width of adult crabs
in the western Gulf of Mexico (146 mm) and is equivalent to
163 g (VanderKooy 2013;Westetal.2016)(Table2).
Fish Mortality
Few studies attempt to estimate fish mortality rates in ghost-
fishing crab traps due to concerns that all estimates under-
represent mortality caused by predation and natural decompo-
sition (e.g., Guillory 1993;Havensetal.2008). Due to a lack
of finfish mortality rates reported in the literature, this analysis
used the results of an 18-month in situ study conducted during
20132014 by LDWF to estimate a finfish capture rate, then
applied professional judgment to estimate a percentage of
captured organisms that are killed in derelict traps. LDWF
set traps in various regions and allowed them to soak for a
specified amount of time (LDWF 2014). The authors returned
to the traps at intervals and recorded the number of non-target
organisms captured (e.g., estuarine fish), in addition to the
species and length of each individual captured in the trap.
Data on the number of species captured per unit time and
the mean size of each species were sorted by location (e.g.,
five waterbodies in Louisiana). We then derived a catch per
unit effort (CPUE) for each month of the survey by dividing
the number of captured organisms by the number of traps
utilized in the survey and by the estimated soak time. The
average annual CPUE estimate was used as the annual fish
capture rate for each waterbody. The mean capture rate de-
rived across Louisiana waterbodies was applied to Texas,
Alabama, Mississippi, and Florida in subsequent calculations
(Table 2).
Similar to Guillory (1993) and Havens et al. (2008), Butler
and Matthews (2015) recorded finfish capture rates and dead
finfish but made no attempt to estimate mortality because the
time between observations was considered to exceed the time
required for a fish carcass to decay or otherwise disappear.
Matthews and Donahue (1997) reported a daily mortality rate
in spiny lobster traps (0.00090.0064 organisms per trap per
day) for all organisms, including finfish, but note the estimate
did not account for fish that might have decayed or been
consumed prior to observation. Based on a literature review
of relevant studies, blue crab capture and mortality rates in
Timbalier Bay, Louisiana, and the Chesapeake Bay were com-
pared, and a ratio of organisms killed to organisms captured
was calculated for both studies (Guillory 1993;Havensetal.
2008). The lower ratio (30%) was applied to the average fin-
fish capture rates in this study to estimate finfish mortality per
trap per year.
For each of the five waterbodies in Louisiana, fish biomass
was calculated using the number of organisms captured and
themeansizeofthoseorganisms (e.g., standard length;
LDWF 2014). The species-specific lengths were converted
to weight through predictable length-weight relationships that
were estimated using FishBase, which pulls from the under-
lying primary literature (Froese and Pauly 2017). For each
waterbody, the mean biomass of species captured in traps
was calculated as a weighted average using the species weight
Table 2 Parameters used to estimate crab and finfish mortality rates in the Gulf of Mexico
Parameter Source Value (units)
Crab mortality rate Literature (Guillory 1993) 26 (crabs trap
1
year
1
)
Individual crab biomass Literature (VanderKooy 2013) 163 (g)
Mean finfish capture rate
a
Derived in this study from data in LDWF 2014 26 (fish trap
1
year
1
)
Proportion of captured finfish killed in traps
b
Literature (Havens et al. 2008; Antonelis et al. 2011)30(%)
Mean finfish biomass
c
LDWF (unpublished data) 357 (g)
a
In Louisiana, average annual finfish capture rates (fish captured per trap per year) were estimated for Pontchartrain (n= 7.4), Barataria (n= 34.0),
Terrebonne (n= 61.6), Vermillion-Teche (n= 17.2), and Sabine (n=9.1) waterbodies. The average capture rate was applied to TX, MS, AL, and FL
waterbodies in the absence of data from site-specific bycatch studies
b
The proportion of captured finfish that are killed in traps has not been directly measured, either in the LDWF study or in the broader literature on this
topic. Based on information related to blue crab capture and mortality rates, here we assume that 30% of captured fish are killed, which is likely an
underestimate of the quick biological turnover within derelict traps (e.g., Antonelis et al. 2011;Bilkovicetal.2012,2016; Havens et al. 2008,2011)
c
In Louisiana, average captured finfish biomass was estimated for Pontchartrain (348 g), Barataria (406 g), Terrebonne (369 g), Vermillion-Teche
(265 g), and Sabine (380 g). The average biomass was applied to TX, MS, and AL waterbodies. Average biomass, accounting for only species found in
Florida, was estimated at 345 g
1825Estuaries and Coasts (2020) 43:1821–1835
and the number of that species captured. Therefore, the esti-
mates calculated for each waterbody in Louisiana reflect the
frequency of capture of certain species at that location
(Table 2). A single weighted average was derived using data
from all five waterbodies and was used in benefit calculations
for Texas, Alabama, and Mississippi (Table 2). Given the dif-
ferent species distributions expected in Florida, a separate
weighted average was derived using only those species ex-
pected to naturally occur along the Florida Gulf coast
(Table 2).
Benefit Calculations
The benefit calculations combine all parameters to estimate
the number and weight of crabs and fish that would not be
killed through a derelict crab trap removal program in 28 GoM
waterbodies (i.e., the mass of organisms that would be killed
in derelict traps if the program did not occur). To reflect the
potential scale of a removal program, we reviewed available
information and consulted with fisheries managers to deter-
mine the percentage of traps that could realistically be re-
moved. This analysis assumed that a removal program would
target 10% of the derelict traps in a given waterbody, and of
the derelict traps targeted, 30% would be ghost fishing based
on the findings of trap removal programs (e.g., Arthur et al.
2014;Giordanoetal.2010;Havensetal.2008). These as-
sumptions were based on values in the peer-reviewed litera-
ture, conversations with fishery managers, and professional
judgment (e.g., Havens et al. 2011; personal communication,
LA Sea Grant). Due to the number of analytical assumptions
that are based on point estimates (e.g., the targeted percent of
derelict traps removed per waterbody) as opposed to data col-
lected or modeled with an underlying distribution, we report
our findings as point estimates and then review the analytical
parameters.
Results
Based on this analysis, a total of 223,000 derelict traps are lost
annually across all waterbodies in the Gulf of Mexico
(Table 3). Notably, Terrebonne Bay and Lake Pontchartrain
account for 51,000 and 49,000 traps, respectively. Derelict
trap density ranges across the GoM from fewer than one to
41 derelict traps per square kilometer and is highest in
Louisianas Terrebonne and Barataria Bays (Table 3).
In addition, the analysis yields a number and biomass of
crabs and fish gained for each year of the removal program, in
each of the 28 waterbodies (Table 4). Maps depicting the
benefits of derelict trap removal programs are presented for
waterbodies in Texas (Fig. 1), Louisiana (Fig. 2), Mississippi
and Alabama (Fig. 3), and Florida (Fig. 4). A removal pro-
gram targeting 10% of the derelict traps generated each year in
the GoM would result in more than 78,000 kg of crabs and
finfish not killed. On a waterbody scale, the benefits of a 1-
year project targeting 10% of derelict traps ranges from 9 to
10,700 kg of crab and 6 to 17,500 kg of fish (Table 4). The
minimum benefits for both crabs and fish are derived in Lower
Laguna Madre, Texas, and maximum benefits are derived in
Terrebonne Bay, Louisiana. The benefits of a 5-year removal
program (Table 5) account for additional benefits in the sec-
ond year for Alabama, Mississippi, and Louisiana (i.e., in
states that do not require a degradable component), due to
the assumption that ghost fishing occurs over the course of
2 years before a trap degrades, and follow the same geograph-
ical trends of a 1-year project. A 5-year program results in a
benefit of 391,000 kg of crab and 300,000 kg of finfish not
killed due to ghost fishing, for a combined benefit of
691,000 kg across the GoM (Table 5).
Discussion
This analysis combined site-specific fisheries data with a trap
loss rate to estimate the number of derelict traps that are added
annually to the Gulf of Mexico. This allowed an estimation of
the likely geographic distribution of derelict crab traps and
development of a resource equivalency analysis model to
quantify the benefits of a removal program for blue crabs
and finfish. By varying the inputs related to the scale of the
program, the proposed analysis can be used by natural re-
source managers to quantify the avoided mortality of crabs
and fish and focus restoration efforts on the most effective
locations. Such a derelict blue crab trap removal program
could replace crabs and fish that were injured as a result of
the Deepwater Horizon oil spill as part of a suite of projects to
restore fish and water column invertebrates (Trustees 2016).
Review of Analytical Parameters
The parameters that drive this analysis of the benefits of trap
removal programs are the number of licenses, latency, the
number of traps used, the rate of trap loss, and mortality rates
in derelict traps. The trap estimates calculated in this paper are
based on more than 10 years of fisheries licensure data and are
robust to fluctuations over time. Fifty percent of license
holders were estimated to be latent, which may underestimate
the number of active blue crab fishers in the GoM but accounts
for the fact that not all commercial license holders are full-time
fishers.
The best available information was used to estimate the
number of traps used by commercial fishers in Louisiana,
Alabama, and Mississippi. These states do not limit the num-
ber of traps for commercial fishers and thus this analysis uses
responses to a fisher survey conducted in Louisiana to deter-
mine an average number of traps. Personal communications
1826 Estuaries and Coasts (2020) 43:1821–1835
with fishery managers and stakeholders indicate that the num-
ber of traps used by fishers may shift over time and with
personal preferences. For example, in Louisiana, some fishers
may use 800 to 1000 traps, while others use 200 to 300.
Further, determining location-specific estimates of fishing ef-
fort is challenging due to privacy laws, and so additional
sources of data that could delineate fishing effort at a more
refined spatial scale are not obtainable. Thus, the average
number of traps used in this analysis may overestimate or
underestimate fishing effort in some waterbodies.
The trap loss rate, set at 25%, may overestimate lost traps in
recreational fisheries and underestimate traps lost in commer-
cial fisheries. For example, it could be easier for recreational
fishers to find and retrieve traps set close to shore or a pier,
although it may also be more convenient to retrieve only the
traps that are easily accessible and allow the others to become
derelict. Awide range of commercial trap loss rates is reported
in the literature, and given the many factors that may lead to
gear loss, it is likely the rate used in this analysis (25% of
actively fished traps) does not overestimate trap loss over
time. For example, severe storms may cause up to 100% loss
and some years may disproportionately contribute to the over-
all loss rate (Guillory et al. 2001b).
The capture and mortality rates derived in this analysis are
quite similar to those calculated in similar studies. For exam-
ple, research in the Chesapeake Bay has determined between
18 and 20 crabs killed per trap per year, with a total of 51 crabs
captured per trap per year (Arthur et al. 2014;Havensetal.
2008). Similarly, in Puget Sound, research studies calculated
mortality and capture rates of 21 and 49 Dungeness crabs per
trap per year, respectively (Antonelis et al. 2011). These esti-
mates align well with the crab mortality rate used in this anal-
ysis (26 crabs per trap per year; Guillory 1993).
In this analysis, the capture rates of finfish varied by an
order of magnitude depending on the location within
Louisiana. This indicates that site-specific estimates of ghost
Table 3 The number of traps used in the fishery, by waterbody, compared with the estimated derelict traps
State Waterbody Traps in fishery Derelict traps
AL Bon Secour Bay/Little Lagoon, Perdido System 2152 538
Mississippi Sound-Mobile 7846 1961
Mobile Bay 23,815 5954
FL Choctawhatchee Bay 3539 885
Pensacola Bay/East Bay/Escambia Bay 5618 1404
Perdido Bay 449 112
St. Andrew Bay/West Bay/North Bay 5618 1404
St. Joseph Bay 955 239
St. Josephs Sound 3202 800
St. Vincent Sound/Apalachicola Bay/East Bay/St George Sound 18,032 4508
Tampa Bay 18,706 4677
LA Atchafalaya, Vermillion, Teche Rivers 131,908 32,977
Barataria Bay 135,279 33,820
Calcasieu, Sabine, Mermentau Rivers 48,234 12,058
Lake Pontchartrain 194,508 48,627
Mississippi River 37,136 9284
Terrebonne Bay 205,058 51,265
MS Hancock Co. 5917 1479
Harrison Co. 3134 784
Jackson Co. 9585 2396
Lake Borgne 3209 802
TX Aransas Bay/Copano Bay 5087 1272
Corpus Christi Bay/Nueces Bay 458 115
Galveston Bay/Trinity Bay 9277 2319
Lower Laguna Madre 294 73
Matagorda Bay/Lavaca Bay 2744 686
Sabine Lake 4450 1113
San Antonio Bay 4833 1208
Gulf of Mexico (combined) 891,042 222,761
1827Estuaries and Coasts (2020) 43:1821–1835
fishing, conducted in each waterbody, may yield different re-
sults than the mean capture and mortality rates derived in
Louisiana and transferred to the other states. Few studies have
estimated the impact of ghost fishing on non-target fish spe-
cies. Research in the Chesapeake Bay has shown 13.6 Atlantic
croakers are caught per trap per season (Havens et al. 2008),
which is comparable with the ghost fishing estimates present-
ed in this paper. Guillory (1993) documented 8.6 fish captured
per trap per year, although escapement and mortality were not
assessed because of the quick degradation and predation on
fish by other organisms within the traps. Thus, the fish capture
rates used in this analysis are comparable with other estimates.
Ultimately, this analysis utilizes available datasets that re-
flect the site-specific ghost fishing impacts in Louisiana,
which is the largest market for the blue crab fishery and ac-
counts for almost 80% of blue crab fishing effort (i.e., traps
used) as well as 78% of blue crab landings across the GoM
(NMFS 2018). Furthermore, this study was designed to utilize
conservative estimates for less certain parameters, which may
therefore underestimate the ecological benefits of trap removal
programs.
Impact of Removal Program
The geographic distribution of derelict traps is an important
consideration when building sustainable removal programs.
Trap density can be usedby state and federal fishery managers
as well as conservation organizations to prioritize trap removal
efforts in easily accessible locations with higher densities of
derelict traps. Implementing a trap removal program in areas
with higher trap densities may lead to greater success in re-
moval operations and thus a greater ecological benefit (Scheld
et al. 2016). Focusing on areas with high trap densities lends a
more efficient cost structure due to decreased time necessary
to remove the targeted numberof traps. Louisiana accounts for
approximately 188,000 derelict traps or 84% of the total der-
elict traps across the GoM. As the Louisiana blue crab fishery
accounts for approximately 78% of the Gulf of Mexicosblue
Table 4 Benefits of a 1-year derelict trap removal project
State Waterbody Blue crab (kg) Finfish (kg) Biomass (kg) Total biomass (kg)
AL Bon Secour Bay/Little Lagoon, Perdido System 112 74 186 2927
Mississippi Sound-Mobile 408 271 679
Mobile Bay 1239 823 2061
FL Choctawhatchee Bay 110 71 181 2875
Pensacola Bay/East Bay/Escambia Bay 175 113 288
Perdido Bay 14 9 23
St. Andrew Bay/West Bay/North Bay 175 113 288
St. Joseph Bay 30 19 49
St. Josephs Sound 100 64 164
St. Vincent Sound/Apalachicola Bay/East Bay/St George Sound 563 361 924
Tampa Bay 584 375 958
LA Atchafalaya, Vermillion, Teche Rivers 6861 2268 9129 69,663
Barataria Bay 7037 7003 14,039
Calcasieu, Sabine, Mermentau Rivers 2509 605 3114
Lake Pontchartrain 10,118 1904 12,021
Mississippi River 1932 1283 3214
Terrebonne Bay 10,666 17,479 28,145
MS
a
Hancock Co. 308 204 512 1891
Harrison Co. 163 108 271
Jackson Co. 499 331 830
Lake Borgne 167 111 278
TX Aransas Bay/Copano Bay 159 105 264 1410
Corpus Christi Bay/Nueces Bay 14 9 24
Galveston Bay/Trinity Bay 290 192 482
Lower Laguna Madre 9 6 15
Matagorda Bay/Lavaca Bay 86 57 142
Sabine Lake 139 92 231
San Antonio Bay 151 100 251
a
Although Lake Borgne is located in Louisiana waters, landings were reported only by Mississippi
1828 Estuaries and Coasts (2020) 43:1821–1835
crab landings (e.g., 18.2 of 23.3 million kilograms in 2016), it
is not surprising that the majority of effort in the GoM blue
crab fishery is distributed across Louisiana or that derelict
traps are concentrated there (NMFS 2018; NOAA 2014).
Blue crab landings revenue across the Gulf of Mexico in-
creased from approximately $46 million in 2007 to $64 mil-
lion in 2016, though landings decreased during that time pe-
riod from 57.9 to 51.3 million pounds (NMFS 2018). The
decrease in landings may explain the increase in price per
pound over time and indicate that fishers could be increasing
fishing effort to meet demand, which could lead to an increase
in derelict fishing traps over time.
The localized trap densities calculated in this paper indicate
a need for ongoing removal programs, particularly focused in
Louisiana waterbodies. Through LDWF, Louisiana runs an
annual derelict crab trap removal program that utilizes volun-
teer support to find and retrieve gear during annual crab fish-
ery closures. In 2018, volunteers removed 4061 traps over 68
boat days, which is a significant investment but does not ap-
proach the 10% figure used in this paper to scale the derelict
trap removal program (i.e., more than 18,000 traps per year).
Funding for the LDWF program is provided in part by the sale
of crab fishing licenses, though further information on costs is
not provided to the public. The Lake Pontchartrain Basin
Foundation, a nonprofit that implements crab trap removal
projects in Louisiana, estimates a cost of between $9 and
$18 per trap removed, focusing on traps that are visible (i.e.,
traps left in the water during the closed season, with an at-
tached float). Based on knowledge of local removal efforts,
the Foundation estimates the Louisiana coastal zone may have
up to 133,000 visible derelict traps and more that are not
visible from the surface, which reinforces our estimate of more
than 188,000 derelict traps across Louisiana (Butcher et al.
2019).
Other derelict trap removal programs have been effectively
implemented at scale, such as the $4.2 million program con-
ducted over 6 years that removed more than 34,000 traps from
the Chesapeake Bay and led to an increase in harvestable
catch valued at more than $20 million (Scheld et al. 2016).
More site-specific information is needed to assess program
Fig. 1 Estimated benefits (kg biomass) of a trap removal program in Texas (derelict crab trap density in parentheses)
1829Estuaries and Coasts (2020) 43:1821–1835
costs in the Gulf of Mexico, as well as the potential impact on
harvestable catch. Based on this analysis, the benefit of a 5-
year removal program in Louisiana translates to more than
352,000 kg of blue crab not killed in derelict traps; if all crabs
were harvestable, this biomass would be valued at more than
$978,000 in 2016 prices. We provide this information for con-
text, as benefit cost analysis was not a stated goal of this study
and our model does not estimate the impact on the value of
harvestable catch.
Future Work to Address Derelict Fishing Traps
This analysis provides quantitative information about the val-
ue of derelict trap removal programs, and could easily act as a
springboard for developing a benefit cost model that targets a
specific program size and location in the Gulf of Mexico, as
well as calculating the benefits of removal programs targeting
other trap fisheries, the ancillary benefits of blue crab trap
removal programs, and the benefits of potential management
measures to reduce the number and impact of derelict traps in
the Gulf of Mexico.
The blue crab fishery is ubiquitous across the GoM and
touches dozens of communities that depend on fisheries as a
way of life. The landings data utilized in this analysis closely
match a recent evaluation of fishing communities. The NOAA
Fisheries Southeast Regional Office published an online tool
of key indicators of fishing communities, including demo-
graphics and dependence on fisheries (NOAA SERO 2017).
Blue crab landings were common throughout all major fishing
communities designated by NOAA. The blue crab fishery is
especially clustered in fishing communities in Louisiana, such
as Terrebonne and Barataria Bays, which have a high density
of derelict traps. In addition to the blue crab fishery, traps are
allowable gear for commercial and recreational fishing in
smaller-scale fisheries across the GoM, including the stone
crab (Menippe mercenaria and M. adina), golden crab
(Geryon fenneri), spiny lobster (Panulirus argus), and octo-
pus (e.g., Octopus vulgaris) fisheries (GMFMC 2010). This
analysis provides a model framework that could be applied to
Fig. 2 Estimated benefits (kg biomass) of a trap removal program in Louisiana (derelict crab trap density in parentheses)
1830 Estuaries and Coasts (2020) 43:1821–1835
other trap fisheries in the GoM to determine the benefits of
additional trap removal programs.
Much of the peer-reviewed and gray literature has focused
on method development for finding and retrieving traps as
well as determining the density of traps in coastal areas across
the USA, as opposed to quantifying the ecological benefits
afforded by habitat restoration through derelict trap removal
programs (e.g., Morison and Murphy 2009; Havens et al.
2008; Maselko et al. 2013;Vossetal.2011). Studies have
published the species captured in traps, usually determined
as part of intermittent volunteer-based trap removal efforts.
Studies of volunteer trap removal efforts (Anderson and
Alford 2014; personal communication, Dr. J. Anderson
Lively, LA Sea Grant) provide information on the ecological
losses associated with ghost fishing inderelict traps. However,
it is not possible to determine realistic catch or mortality rates
solely from data collected during trap removal programs. The
LDWF study is one of the most comprehensive ghost fishing
assessments available, though it is important to note that the
ghost fishing estimates are reflective of a single point in time
when the traps were removed and the ghost fishing was
assessed (LDWF 2014). Without underwater observation of
the traps, accurate estimates of both capture and mortality of
bycatch are elusive and a derived ghost-fishing rate will not
fully represent mortality due to the quick turnover of organism
remains in traps through degradation and consumption by
other captured individuals (see, e.g., Guillory 1993). While
this paper relies on the best available information to derive
the benefits of removal programs, there is a scarcity of in situ
measurements to corroborate the assumptions across the
GoM. For example, restoration-focused studies could further
investigate the role of location, ghost fishing duration, mortal-
ity rates for bycatch species, and how environmental factors
affect trap functionality.
Traps lost or abandoned in one location may be transported
across state boundaries and reach inshore and offshore habi-
tats far from the initial point of loss. More information from
field surveys is needed to create probability distributions for
derelict gear aggregations across the GoM. Future in situ stud-
ies could investigate the range of physical and chemical
Fig. 3 Estimated benefits (kg biomass) of a trap removal program in Mississippi and Alabama (derelict crab trap density in parentheses)
1831Estuaries and Coasts (2020) 43:1821–1835
oceanographic parameters that affect trap loss, movement, and
degradation; for example, depth, water clarity, suspended
solids, dissolved oxygen, microbial activity, siltation, benthic
cover (i.e., softbottom versus hard bottom or reef habitat), and
remaining buoy attachments likely play a role in how quickly
traps degrade or are made ineffective through burial and re-
moval (Butler and Matthews 2015; Lewis et al. 2009; Uhrin
et al. 2014). Future field studies and/or restoration pilot pro-
jects in the GoM could ground-truth our benefit estimates.
The number of derelict traps targeted in a removal program
has a large impact on the benefit of that program, such that
doubling the number of removed traps doubles the expected
benefit. Consistent with the findings and recommendations of
Scheld et al. (2016), focusing removal efforts on waterbodies
with the highest densities of derelict traps is the best strategy
to maximize the benefits and minimize the cost of the removal
program. Scheld et al. (2016) found that the difference be-
tween average benefits and costs per pot removed was highest
when derelict gear hotspots were targeted. Resource managers
can utilize the model developed in this analysis to determine
the relative GoM hotspots where derelict crab traps are gen-
erated, and therefore the locations that possess the greatest
benefits for concentrated removal programs. Side-scan sonar
may be used to estimate the number and density of derelict
traps in GoM waterbodies. Better-informed loss rates could be
determined through fisher surveys or estimates of crab trap
sales. Additional in situ restoration monitoring studies may
be conducted in tandem with trap removal programs to inves-
tigate site-specific differences in the species impacted and
therefore the ecological benefits derived from a removal
project.
However, even with additional field studies and more effi-
cient removal programs, a significant amount of gear is likely
to be lost or abandoned. In fact, as noted in Martens and
Huntington (2012), it is likely that the in situ debris supply
exceeds potential removal efforts. As such, sustained and ad-
equately funded removal programs are necessary to mitigate
the continued impacts and continuous resupply of derelict
traps (GSMFC 2015). In the absence of management options
that limit the impact of derelict traps, such as degradable
Fig. 4 Estimated benefits (kg biomass) of a trap removal program on the west coast of Florida (derelict crab trap density in parentheses)
1832 Estuaries and Coasts (2020) 43:1821–1835
panels that allow trapped organisms to escape unharmed, der-
elict traps will continue to have the same impact over time.
Some states have legislated measures such as cull rings and
degradable panels, though the impact of these devices on the
ghost fishing capability of a derelict trap has not been studied
in the GoM. Assuming additional supporting data become
available, the model developed here could be used to assess
the benefits of such management measures.
Likewise, future assessments could investigate the eco-
nomic impacts of derelict traps on GoM fishing communities
to provide added support and/or direction to derelict trap re-
moval programs. A reduction in the number of derelict blue
crab traps would lead to increases in crab and finfish biomass,
economic benefits to fishing communities, and ancillary ben-
efits such as reduced interaction with marine mammals, sea
turtles, and boating traffic. Calculating the economic impact
of restoration benefits is a logical extension of this paper, and
would create a more complete understanding of the benefits
and costs of derelict trap removal programs.
Acknowledgments We thank Drs. Julie Anderson Lively and Joan
Browder for assistance in gathering data and discussing rationale behind
certain model parameters, Amy Uhrin for reviewing this manuscript and
providing valuable feedback, and Meredith Amend and Ellen Plane for
assistance with mapping. We also thank two anonymous reviewers for
their careful review and considered feedback.
Funding Information Funding of this study and production of this pub-
lication was provided by the Federal and State Natural Resource
Agencies(Trustees) Natural Resource Damage Assessment (NRDA)
for the Deepwater Horizon (DWH) oil spill through the National
Oceanic and Atmospheric Administration (NOAA) Damage
Assessment, Remediation and Restoration Program (DARRP) (NOAA
Contract No. AB133C-11-CQ-0050).
Compliance with Ethical Standards
Conflict of Interest The authors declare that they have no conflict of
interest.
Disclaimer The scientific results and conclusion of this publication, as
well as any views or opinions expressed herein, are those of the authors
and do not necessarily represent the view of NOAA or any other natural
Table 5 Benefits of a 5-year derelict trap removal project
State Waterbody Blue crab (kg) Finfish (kg) Biomass (kg) Total biomass (kg)
AL Bon Secour Bay/Little Lagoon, Perdido System 1008 669 1677 26,340
Mississippi Sound-Mobile 3673 2439 6112
Mobile Bay 11,149 7403 18,552
FL Choctawhatchee Bay 552 354 907 14,377
Pensacola Bay/East Bay/Escambia Bay 877 563 1439
Perdido Bay 70 45 115
St. Andrew Bay/West Bay/North Bay 877 563 1439
St. Joseph Bay 149 96 245
St. Josephs Sound 500 321 820
St. Vincent Sound/Apalachicola Bay/East Bay/St George Sound 2814 1806 4620
Tampa Bay 2919 1873 4792
LA Atchafalaya, Vermillion, Teche Rivers 61,752 20,410 82,162 626,968
Barataria Bay 63,330 63,024 126,354
Calcasieu, Sabine, Mermentau Rivers 22,580 5444 28,024
Lake Pontchartrain 91,058 17,134 108,191
Mississippi River 17,385 11,544 28,929
Terrebonne Bay 95,997 157,311 253,307
MS Hancock Co. 2770 1839 4609 17,017
Harrison Co. 1467 974 2442
Jackson Co. 4487 2980 7467
Lake Borgne 1502 997 2500
TX Aransas Bay/Copano Bay 794 527 1321 7048
Corpus Christi Bay/Nueces Bay 71 47 119
Galveston Bay/Trinity Bay 1448 961 2409
Lower Laguna Madre 46 30 76
Matagorda Bay/Lavaca Bay 428 284 712
Sabine Lake 694 461 1156
San Antonio Bay 754 501 1255
1833Estuaries and Coasts (2020) 43:1821–1835
resource Trustee for the BP/Deepwater Horizon NRDA. Any use oftrade,
firm, or product names is for descriptive purposes only and does not
imply endorsement by the U.S. Government. This publication does not
constitute an endorsement of any commercial product or intend to be an
opinion beyond scientific or other results obtained by NOAA.
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... Derelict crab traps are a common type of DFG that are found globally and are responsible for significant ecological (e.g. ghost fishing; damage or reduce submerged aquatic vegetation) and economic impacts (Arthur et al., 2020). These crab traps are often lost when the lines attaching the traps to a float are broken by wave action or severed by propellers, which makes the now unmarked traps difficult to recover. ...
... Posadas et al. (2021) documented that shrimpers most often interact with derelict crab traps compared to other types of marine debris and DFG. This finding isn't surprising since recent estimates are that 25 % of all crab traps in the Mississippi, Louisiana, and Alabama blue crab fisheries are derelict (Arthur et al., 2020). Qualitative studies of Mississippi shrimpers have shown they frequently encounter marine debris, mostly DFG, and it has significant impacts on their operations, indicating that marine debris has a large impact on the industry . ...
... Crabbers use metal traps that sit on the seafloor with a buoy attached to mark their location. To increase productivity, crabbers typically drop their traps near each other (Vincent et al., 2001;Arthur et al., 2020); resulting in the clustered pattern observed with the nearest neighbor analysis. These traps are not extremely mobile except for being dragged by a boat's propellors or strong storm surges affecting the currents and dragging them across the seafloor (Vincent et al., 2001), and once crab traps are abandoned or lost at sea, they are considered marine debris (Arthur et al., 2020). ...
Article
The commercial shrimping industry is subjected to myriad stressors that have led to financial hardships among industry members. One of these stressors is marine debris; however, there is limited understanding of the type and magnitude of impacts. Quantitative methods of estimating the economic impacts of marine debris on the commercial shrimping industry were developed. From June to December 2019, participating shrimpers submitted 393 daily summaries, including shrimping activities, marine debris encounters, damages, and impacts. The impacts of marine debris encounters were assessed from reports of daily damages to fishing assets, daily lost fishing time, daily loss-catch ratios, and daily catch losses. The results of this study demonstrate substantial negative economic impacts on commercial shrimpers related to marine debris encounters. About 17 % of shrimp caught were lost due to marine debris encounters, resulting in foregone total sales and job impacts of $3.2 million and 33 jobs in shrimping and associated businesses.
... Derelict crab traps are a common type of DFG that are found globally and are responsible for significant ecological (e.g. ghost fishing; damage or reduce submerged aquatic vegetation) and economic impacts (Arthur et al., 2020). These crab traps are often lost when the lines attaching the traps to a float are broken by wave action or severed by propellers, which makes the now unmarked traps difficult to recover. ...
... Posadas et al. (2021) documented that shrimpers most often interact with derelict crab traps compared to other types of marine debris and DFG. This finding isn't surprising since recent estimates are that 25 % of all crab traps in the Mississippi, Louisiana, and Alabama blue crab fisheries are derelict (Arthur et al., 2020). Qualitative studies of Mississippi shrimpers have shown they frequently encounter marine debris, mostly DFG, and it has significant impacts on their operations, indicating that marine debris has a large impact on the industry . ...
... Crabbers use metal traps that sit on the seafloor with a buoy attached to mark their location. To increase productivity, crabbers typically drop their traps near each other (Vincent et al., 2001;Arthur et al., 2020); resulting in the clustered pattern observed with the nearest neighbor analysis. These traps are not extremely mobile except for being dragged by a boat's propellors or strong storm surges affecting the currents and dragging them across the seafloor (Vincent et al., 2001), and once crab traps are abandoned or lost at sea, they are considered marine debris (Arthur et al., 2020). ...
... Derelict crab traps are a common type of DFG that are found globally and are responsible for significant ecological (e.g. ghost fishing; damage or reduce submerged aquatic vegetation) and economic impacts (Arthur et al., 2020). These crab traps are often lost when the lines attaching the traps to a float are broken by wave action or severed by propellers, which makes the now unmarked traps difficult to recover. ...
... Posadas et al. (2021) documented that shrimpers most often interact with derelict crab traps compared to other types of marine debris and DFG. This finding isn't surprising since recent estimates are that 25 % of all crab traps in the Mississippi, Louisiana, and Alabama blue crab fisheries are derelict (Arthur et al., 2020). Qualitative studies of Mississippi shrimpers have shown they frequently encounter marine debris, mostly DFG, and it has significant impacts on their operations, indicating that marine debris has a large impact on the industry . ...
... Crabbers use metal traps that sit on the seafloor with a buoy attached to mark their location. To increase productivity, crabbers typically drop their traps near each other (Vincent et al., 2001;Arthur et al., 2020); resulting in the clustered pattern observed with the nearest neighbor analysis. These traps are not extremely mobile except for being dragged by a boat's propellors or strong storm surges affecting the currents and dragging them across the seafloor (Vincent et al., 2001), and once crab traps are abandoned or lost at sea, they are considered marine debris (Arthur et al., 2020). ...
Article
Commercial shrimpers frequently encounter marine debris in their nets, resulting in economic impacts. Currently, no information existed on the spatial and temporal distribution of marine debris that shrimpers encounter and the subsequent economic impact on commercial shrimping. Twenty commercial shrimpers participated in a comprehensive data collection program (July 2020 through December 2020) within the north-central Gulf of Mexico, USA to characterize the quantity and impacts of marine debris. Derelict crab traps were an overwhelming issue for shrimpers. The type of fishing gear used influenced the type of marine debris encountered and the subsequent economic impacts. Surveyed shrimpers encountered marine debris on 19 % of tows and lost an average of 18.21 min, 7.88 kg of catch, and 6.37ingeardamagepertowwithencounters,resultinginaverageannuallossesof6.37 in gear damage per tow with encounters, resulting in average annual losses of 6601 per shrimper. The results of this study show that marine debris encounters can have a large impact on the commercial shrimping industry.
... Until recent years, there have been few studies on the extent of the issue and efforts to remove derelict crab traps (Arthur et al., 2014). Arthur et al. (2020) analyzed the benefits of derelict trap cleanups throughout the Gulf States and found that derelict fishing gear focused cleanups would be beneficial for the economy, multiple fisheries, recreational boaters, and other aquatic wildlife. A 4-year program in which derelict fishing gear was removed, including over 31,000 crab traps, from the Chesapeake Bay, showed that lost blue crab traps are a significant source of marine debris (Bilkovic et al., 2014). ...
... Scheld et al. (2016) analyzed derelict crab traps and the benefits on a global scale and found that about $831 million in landings from major crustacean fisheries could be recovered annually by removing <10 % of the derelict crab traps. These studies, however, only estimate the economic impacts derelict crab traps have on the blue crab fisheries (Scheld et al., 2016;Bilkovic et al., 2014;Arthur et al., 2014Arthur et al., , 2020 and do not discuss the economic impacts on any other fisheries. Most derelict crab trap cleanups in the region focus on nearshore traps in shallow waters for shrimpers to encounter (Mississippi Department of Marine Resources (MDMR), 2022). ...
... There are an estimated 22,000 actively fished crab traps in the Mississippi state fishery, and nearly 5500 of those are estimated to be lost each year (Arthur et al., 2020). This high concentration of derelict crab traps, documented impacts on the shrimping industry, and the laws in this area that allow for commercial shrimpers to possess derelict crab traps (Miss. ...
Article
Due to fishery-tailored gear, shrimpers are often affected by benthic marine debris, specifically derelict crab traps. To alleviate the impacts on the commercial shrimping industry in the Mississippi Sound, a team of natural resource professionals and stakeholders developed a derelict crab trap removal incentive program for commercial shrimpers. In three years, this program led to the removal of 2904 derelict crab traps from the north-central Gulf of Mexico at a total average cost of 35,595peryeartoimplementtheprogram,or35,595 per year to implement the program, or 53 per derelict crab trap. Results from this study showed the cost of the program could further be reduced while covering the same shrimping area, through the inclusion of fewer disposal locations and targeting active and engaged shrimpers. This program led to the removal of crab traps by non-registered shrimpers, indicating that the existence of the program and associated outreach could lead to improved environmental stewardship without an incentive.
... Ghost fishing affects threatened bycatch species as well as target species [10,164,87]. Robust estimates of ghost fishing removals of threatened and marketable species have been based on observations from recovered derelict gear [11,84,85]. For example, through gear retrieval (both of derelict and in-use illegal gear), Aceves-Bueno [2] identified ghost fishing impacts of ALDFG in the illegal Mexican totoaba swim bladder gillnet fishery. ...
Article
The rapid expansion of the global footprint of marine capture fisheries over recent decades, combined with the transition to synthetic and more durable materials used for fishing gear components, has resulted in increasingly problematic adverse ecological and socioeconomic effects from abandoned, lost and discarded fishing gear (ALDFG). Adverse impacts include: ghost fishing; marine wildlife ingestion; distribution and transfer of toxins and microplastics into marine food webs; altered distributions and behavior of species that raft on or aggregate beneath floating ALDFG, including the transport of invasive non-native species and distribution of microalgae that cause harmful algal blooms. ALDFG also causes habitat degradation; obstruction and damage to maritime sectors such as from fouling marine vessels and damaging submarine cables and in-use fishing gear; and reduction of socioeconomic values of coastal areas. There has been growing recognition of the need for improved understanding and evidence-informed management of these adverse effects. The articles composing the Marine Policy special issue on ALDFG contribute to achieving this goal. The articles improve the understanding of key requirements for robust, effective ALDFG monitoring and management. This includes knowledge of ALDFG direct causes and underlying drivers, rates and magnitudes of production, composition, fate, ecological and socioeconomic impacts, and criteria for selecting fishery-specific management strategies, which we review in this introduction to the special issue.
... Beyond the impacts on ecosystem services as reported, ALDFG and ghost fishing have been estimated to generate significant economic losses [1,17,19,43,46]. Market price method basically uses the market price of caught species at the studied point of time and assumes a fixed catch rate per period, usually a year [4,17,36]. ...
Article
Full-text available
Abandoned, lost, and discarded fishing gear (ALDFG) is claimed to be a global problem with impacts on marine animals and ecosystems, posing considerable ecological and socioeconomic challenges. Nonetheless, insufficient understanding regarding how marine ecosystem services are affected by ALDFG creates a knowledge gap that challenges a holistic estimation of the long-term economic impacts of using non-degradable fishing gear. In this study, a systematic review and meta-analysis of the existing literature on ALDFG and ghost fishing is conducted, with the aim to assess findings in the literature and identify knowledge gaps. 90 published works were included in the systematic review, of which 67 were examined further in the meta-analysis. We identified a limited number of economic studies, as well as research from developing countries. Focus is largely on ghost fished commercial species, while other species, and non-use values are largely ignored. Though provisioning, supporting and cultural services are represented in the studies, regulating services impacted for instance by the marine plastic pollution of ALDFG, received no attention. Expanding research to include more of these currently lacking elements may be vital for efficient management in relation to ALDFG.
... Ghost fishing refers to fishing by gear that is lost or abandoned and no longer tended but continues to capture organisms. Crab traps and lobster pots are of particular concern in the nearshore GOM and may unintentionally fish for years before degrading to the point that they are no longer fishing, contributing substantial mortality to affected nearshore species (Butler & Matthews, 2015;Arthur et al., 2020). Gill nets and other fishing gear are also present and can cause mortality if lost or abandoned; however, they are typically lost less frequently than trap gears (Richardson et al., 2019). ...
Preprint
Full-text available
The Deepwater Horizon Open Ocean Trustee Implementation Group (OO TIG) and the Core Fish Team, a planning team composed of representatives from federal trustee agencies, developed a strategic plan to inform future Fish and Water Column Invertebrates (FWCI) restoration under the Natural Resource Damage Assessment (NRDA). The purpose of this strategic plan is to guide restoration planning for FWCI by establishing a process that prioritizes species for restoration, identifies threats to, and associated restoration opportunities for injured species, and establishes and prioritizes restoration objectives. Additionally, this document identifies strategic considerations for project implementation and data gaps that are identified during the strategic planning process. This plan incorporates prior restoration planning and projects. It also builds on the injury assessment and restoration goals identified in the Deepwater Horizon (DWH) Programmatic Damage Assessment and Restoration Plan (DWH NRDA Trustees, 2016) for restoring FWCI resources.
... ALDFG can capture and kill economically valuable species as well as threatened species for a long duration, known as 'ghost fishing'. ALDFG also can damage facilities built in or near the sea [3,4,6,8,[15][16][17][18]21]. ...
Article
Derelict fishing gear causes substantial adverse ecological and socioeconomic impacts. This study determined the rate of production of derelict gear from an Iranian Persian Gulf fishery using a type of fishing pot regionally known as gargoor. From November 2018 to July 2020, fishermen were surveyed and pots were marked in Jofreh, Jalali and Ganaveh, which are three major areas of Iran’s coastal waters. We tagged 1,565 pots from 15 fishing vessels, which were then monitored throughout the study period, and surveyed 240 fishermen. Only 1% of tagged pots were retrieved, with 43% having been lost and 56% abandoned or discarded. Similarly, surveyed fishermen estimated losing 20% and abandoning or discarding 76% of pots, retrieving only 4%. Fishermen from the three study areas were estimated to annually produce over 287,000 derelict pots. Main causes of the production of abandoned, lost and discarded fishing gear were: (1) gear conflicts with shrimp trawls, anchored gillnets and strings of pots; (2) inclement weather; (3) strong currents; and (4) at the end of fishing season, abandonment and discarding of end-of-life pots. Potential solutions to the abandonment and discarding of pots at the end of fishing seasons, which was the largest source of derelict gear production in this fishery, include: increased awareness by fishermen of the adverse effects of derelict pots, development of more durable gear components that enable pots to last for multiple seasons, and detection and removal of derelict pots. Potential solutions to gear loss include: zoning to spatially and temporarily separate fisheries with gear conflicts, improved communication between vessels to avoid gear conflicts, training for new entrants, gear marking to enhance pot gear visibility in areas where theft is a low risk, and avoidance of fishing during inclement weather. These findings of extremely high rates of derelict gear production from Iranian pot fisheries in the Persian Gulf and identification of causes for abandonment, loss and discarding of fishing gear highlight the urgent need to introduce relevant mitigation interventions.
... A similar framework applies for evaluating ghost fishing impacts of the same piece of debris. Derelict fishing gear has the capacity to continue to catch and kill animals until it degrades or is removed (Arthur et al. 2020;Butler and Matthews 2015;Matsuoka et al. 2005). Fig. 3 below indicates the lost resource services from derelict fishing gear (area E + F), and the benefits (injury foregone) of removing the same piece of derelict gear at year 2 (area F). ...
Article
Full-text available
While knowledge of the ecological impacts of marine debris is continually advancing, methods to evaluate the comparative scale of these impacts are less well developed. In the case of costly environmental restoration in marine and coastal environments, quantifying and comparing the ecological impacts of diverse forms of ecosystem injuries can facilitate a more efficient selection of restoration projects. This article proposes evaluating marine debris removal projects in an ecological service equivalency analysis framework that can be used to compare marine debris removal to other types of environmental restoration. Drawing on existing spatial and temporal data with respect to marine debris impacts on habitats and resources, we demonstrate how resource managers and organizations involved in marine debris removal can quantify the ecological service benefits of a removal project and use it to comparatively select between projects based on present value ecological benefits. This valuation can be useful in natural resource damage assessment restoration selection, and for directing limited funds to marine debris removal projects which produce the greatest gains in ecological services. This ecological scaling framework is applied to a seagrass injury case study to demonstrate its application for scaling marine debris removal as compensatory restoration.
Article
Traps (or pots) are one of the oldest and most widespread scientific survey gears for fish and decapod crustaceans around the world. Here, I review and synthesize the extensive scientific literature describing the various benefits and drawbacks of using traps as a survey gear in scientific studies. The widespread use of traps in fish and decapod surveys is due to several characteristics like their low cost, flexible design, ease of use, ability to fish unattended, and being amenable to pairing with other gears. However, there are a number of significant drawbacks of using traps, including highly variable catches due to environmental fluctuations or behavioral interactions or lost traps that continue catching and killing animals, that must be considered and accounted for when initiating trap surveys. This study highlights the types of habitats and species most and least suited for monitoring by traps, and emphasizes the importance of matching the goals and objectives of a trap survey with the correct trap design, mouth entrance, bait type, soak time, and pairing of gears. Pilot studies are also recommended before surveys are initiated to quantify the selectivity patterns of traps and identify the various factors that may influence trap catch.
Article
Full-text available
Natural resource trustee agencies must determine how much, and what type of environmental restoration will compensate for injuries to natural resources that result from releases of hazardous substances or oil spills. To fulfill this need, trustees, and other natural resource damage assessment (NRDA) practitioners have relied on a variety of approaches, including habitat equivalency analysis (HEA) and resource equivalency analysis (REA). The purpose of this paper is to introduce the Habitat-Based Resource Equivalency Method (HaBREM), which integrates REA's reproducible injury metrics and population modeling with HEA's comprehensive habitat approach to restoration. HaBREM is intended to evaluate injury and restoration using organisms that use the habitat to represent ecological habitat functions. This paper seeks to expand and refine the use of organism-based metrics (biomass-based REA), providing an opportunity to integrate sublethal injuries to multiple species, as well as the potential to include error rates for injury and restoration parameters. Applied by NRDA practitioners in the appropriate context, this methodology can establish the relationship between benefits of compensatory restoration projects and injuries to plant or animal species within an affected habitat. HaBREM may be most effective where there are appropriate data supporting the linkage between habitat and species gains (particularly regionally specific habitat information), as well as species-specific monitoring data and predictions on the growth, density, productivity (i.e., rate of generation of biomass or individuals), and age distributions of indicator species.
Technical Report
Full-text available
Executive Summary Derelict fishing gear represents a major challenge to marine resource management: whether through deliberate abandonment or through accidental loss, derelict traps in particular have significant negative effects both economic (e.g., reduced fishery harvest from ghost fishing and gear competition that leads to the reduced efficiency of active gear) and ecological (e.g., degraded habitats and marine food webs and crab and bycatch mortality). Throughout the Chesapeake Bay, commercial harvest of hard-shelled blue crabs is a major fishing activity: every year sees the deployment of several hundred thousand blue crab traps (known locally as crab “pots”) across the Bay, of which an estimated 12-20% are lost each year. This report focuses on these derelict crab pots, drawing on many direct or remote observations and other data to quantify their abundance and spatial distribution across the Chesapeake Bay, and their resulting ecological and economic effects. The study used a unified geostatistical framework to integrate disparate spatial datasets to predict the distribution and abundance of derelict crab pots in Chesapeake Bay and to evaluate their adverse effects on sensitive habitats and bay species. Predictor variables that likely affect the distribution and abundance of derelict crab pots that were evaluated included fishing effort, recreational boating activity, marine traffic patterns, and water depth. Using all of these data inputs, as well as derelict pot removal data and derelict pot field surveys, a geographically weighted regression (GWR) model successfully predicted and mapped the densities of derelict pots throughout the Chesapeake Bay, and estimated over 145,000 derelict pots Bay-wide; about 58,000 in Maryland and 87,000 in Virginia. An inventory of data available from many different sources identified several crucial but unknown variables necessary to evaluate ecological impacts of derelict crab pots baywide, such as pot loss rates, fishing practices affecting pot loss, and escape and mortality rates for crabs and bycatch (non-crab species) caught in derelict crab pots. These “data gaps” were filled through fieldwork (inspection and removal of derelict crab pots), controlled laboratory observations of crabs in and near pots, and structured conversations with watermen. The predicted geographic distribution of these pots served to pinpoint areas with significant ecological impacts: by combining the numbers and distribution of derelict pots from this model with annual blue crab catch and mortality rates, we estimate that each year, derelict pots catch over 6 million crabs, and kill over 3.3 million — 4.5% of the 73 million crabs harvested in 2014. The effects on bycatch are also significant: for example, our model estimates that each year, derelict pots entrap over 3.5 million white perch and nearly 3.6 million Atlantic croaker across the Bay. The effects of derelict pots on marine habitats appear to be less significant: only 16% of predicted derelict pots are in areas with submerged aquatic vegetation; and only 2% are in oyster beds. However, derelict pot removal programs required the avoidance of sensitive habitats including SAV and oyster reefs; therefore the impact on habitats may be greater. Next, a spatially explicit harvest model was used to predict the economic effect of pot removal efforts on commercial blue crab harvests, by comparing actual harvests (with the derelict pot removals that occurred from 2008-2014) against those one would have expected in a counterfactual scenario of zero derelict pot removals. Model results suggest that pot removals increased harvests by over 30 million lbs in Virginia (27.2%, valued at 22.6million)andover8millionlbsinMaryland(16.322.6 million) and over 8 million lbs in Maryland (16.3%, valued at 10.9 million); for a Bay-wide total of over 38 million lbs (23.8%, valued at $33.5 million) over the 6 year period. The model also suggested that over the derelict pot removal period, pot removals increased the efficiency of active pots by 0.43 lbs/pot in Chesapeake Bay; so on average, for each pot removed, harvests increased by 868 lbs. Finally, the removal of derelict pots from high intensity potting areas (hotspots) can produce significant economic benefit beyond reducing mortality. For example, removing as little as 10% of the derelict pots from the 10 most heavily fished sites (5 sites in Virginia; 5 in Maryland) could increase blue crab harvest in the Chesapeake Bay by 22 million pounds or approximately 14%. These findings suggest several spatially-explicit management actions likely to reduce derelict crab pot accumulations and their harmful effects in the Chesapeake Bay. Minimizing spatial conflicts between crabbing and recreational and commercial boating traffic, and educating vessel operators on pot avoidance, would greatly reduce pot loss. Targeted pot removals in heavily-fished areas would be a highly cost-effective way to increase catch efficiency and reduce bycatch mortality. The number and impact of derelict pots would also be reduced by incentives to accelerate the removal of abandoned pots and to modify crab pots with biodegradable escape panels. We can already quantify the effects of some of these mitigation measures: for example, biodegradable escape panels would likely reduce crab mortality in derelict pots from over 3.3 million per year (4.5% of the harvest) to under 440,000 (0.6%). The report discusses the sensitivity of these findings to the various inputs; as well as the confidence and precision levels attainable with current data; and charts ways to further refine these results to inform a generalized framework for determining ecological and economic effects of derelict fishing gear that can be used in similar fisheries in the United States and elsewhere. Appendices to the report - some of which are full research reports in their own right - provide crucial detail and context. Appendix A documents the fieldwork, analysis, and findings related to loss rates of blue crab pots. Appendix B records the laboratory (mesocosm) study of capture, escape, and mortality rates for crabs in derelict pots. Other appendices detail the data used in the study; the complex and changing regulatory context for blue crab management across the Bay; the team’s outreach activities over the course of the project; the template for conversations with watermen; and a published article detailing the economic effects analysis.
Article
Full-text available
Every year, millions of pots and traps are lost in crustacean fisheries around the world. Derelict fishing gear has been found to produce several harmful environmental and ecological effects, however socioeconomic consequences have been investigated less frequently. We analyze the economic effects of a substantial derelict pot removal program in the largest estuary of the United States, the Chesapeake Bay. By combining spatially resolved data on derelict pot removals with commercial blue crab (Callinectes sapidus) harvests and effort, we show that removing 34,408 derelict pots led to significant gains in gear efficiency and an additional 13,504 MT in harvest valued at US 21.3milliona2721.3 million—a 27% increase above that which would have occurred without removals. Model results are extended to a global analysis where it is seen that US 831 million in landings could be recovered annually by removing less than 10% of the derelict pots and traps from major crustacean fisheries. An unfortunate common pool externality, the degradation of marine environments is detrimental not only to marine organisms and biota, but also to those individuals and communities whose livelihoods and culture depend on profitable and sustainable marine resource use.
Article
Full-text available
In the Florida Keys, traps for spiny lobsters (also known as Caribbean spiny lobster) Panulirus argus are often deployed in seagrass beds. Given that several hundred thousand traps may be deployed in one fishing season, the possibility exists for significant impacts to seagrass resources. The question was whether standard fishing practices observed in the fishery actually resulted in injmies to seagrass. This study was designed to measure the degree of injury to seagrass as a function of trap deployment duration (soak time) and habitat type (seagrass species) and the recovery of seagrass following trap removal. Aspects of the deployment and retrieval process were not examined. Sampling grids composed of 30 3-m x 3-m squares were arbitrarily established within each of three monospecific seagrassbeds (two of Thalassia testudinum and one of Syringodium filiforme) near Marathon, Florida. Five squares within each grid remained trap-free (controls) while the remaining squares each received a single trap. Five traps from each grid were randomly removed at each of five soak times (ranging from 1 to 24 weeks). Immediately before deployment and following trap removal, seagrass short shoot densities were recorded and compared among controls and treatments. Both seagrass species exhibited significantly decreased shoot densities after 6-week and 24-week soak times. Thalassia testudinum densities within the 6-week and 24-week treatments had returned to control densities 4 months after trap removal, while densities of S. filiforme remained significantly decreased at the end of 24 weeks. We conclude that traps must be recovered within a 6-week period, beyond which injury to seagrass beds is predicted, with long lasting effects to beds of S. filifonne. Within the limits of these testing parameters, it appears that standard fishing practices (typically < 5-week soak time) should not result in a significant injury to seagrass beds in the Florida Keys.
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