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An assessment of a bait industry and angler behavior as a vector of invasive species

  • Maryland Department of Natural Resources (retired)

Abstract and Figures

The use of live bait by anglers is an important vector of both aquatic and terrestrial invasive species. Bait-bucket introductions of invasive crayfishes, fishes, earthworms, pathogens, and other organisms have reduced biodiversity and altered ecosystem function and structure throughout the United States, including the Mid-Atlantic region. In 2008, we conducted a telephone survey of bait shops and a mail survey of anglers to obtain information on the trade and use of bait in Maryland, a US state with many introduced bait species. Our telephone survey of bait shops confirmed that this industry is a source of non-native and invasive species in Maryland. Our survey documented at least six non-native bait species for sale in the state. With the exception of a few locally collected bait species, bait sold in Maryland originated from sources outside of the state, and in some cases, outside the Mid-Atlantic region. Results of our angler survey indicated that 64% of Maryland freshwater anglers, both resident and non-resident, used live bait and that the release of unused live bait was quite common and occurred statewide. The release of unused bait by anglers varied with bait type. Anglers more readily released aquatic than terrestrial baits. For example, 65 and 69% of Maryland anglers using fishes and crayfishes released their unused bait; whereas only 18 and 10% of anglers released their unused earthworms and grubs-mealworms-maggots, respectively. Our surveys indicated that any non-native, potentially invasive species imported into the state via the bait industry is likely to be released by anglers into Maryland’s aquatic and terrestrial ecosystems. Many of these species have the potential to become established in the state. These results illustrate the need for greater oversight of the bait industry, development of consistent regulations on bait use, and a region-wide education campaign aimed at changing anglers’ behavior regarding bait use and its disposal. We recommend specific management actions that, if implemented, would greatly reduce further bait-bucket introductions and provide protection against invasive bait species in Maryland and the Mid-Atlantic region.
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1 23
Biological Invasions
ISSN 1387-3547
Volume 14
Number 7
Biol Invasions (2012) 14:1469-1481
DOI 10.1007/s10530-012-0173-5
An assessment of a bait industry and angler
behavior as a vector of invasive species
Jay V.Kilian, Ronald J.Klauda, Sarah
Widman, Michael Kashiwagi, Rebecca
Bourquin, Sara Weglein & John Schuster
1 23
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An assessment of a bait industry and angler behavior
as a vector of invasive species
Jay V. Kilian Ronald J. Klauda
Sarah Widman Michael Kashiwagi
Rebecca Bourquin Sara Weglein John Schuster
Received: 2 March 2011 / Accepted: 9 January 2012 / Published online: 20 January 2012
Springer Science+Business Media B.V. 2012
Abstract The use of live bait by anglers is an
important vector of both aquatic and terrestrial inva-
sive species. Bait-bucket introductions of invasive
crayfishes, fishes, earthworms, pathogens, and other
organisms have reduced biodiversity and altered
ecosystem function and structure throughout the
United States, including the Mid-Atlantic region. In
2008, we conducted a telephone survey of bait shops
and a mail survey of anglers to obtain information on
the trade and use of bait in Maryland, a US state with
many introduced bait species. Our telephone survey of
bait shops confirmed that this industry is a source of
non-native and invasive species in Maryland. Our
survey documented at least six non-native bait species
for sale in the state. With the exception of a few locally
collected bait species, bait sold in Maryland originated
from sources outside of the state, and in some cases,
outside the Mid-Atlantic region. Results of our angler
survey indicated that 64% of Maryland freshwater
anglers, both resident and non-resident, used live bait
and that the release of unused live bait was quite
common and occurred statewide. The release of
unused bait by anglers varied with bait type. Anglers
more readily released aquatic than terrestrial baits. For
example, 65 and 69% of Maryland anglers using fishes
and crayfishes released their unused bait; whereas only
18 and 10% of anglers released their unused earth-
worms and grubs-mealworms-maggots, respectively.
Our surveys indicated that any non-native, potentially
invasive species imported into the state via the bait
industry is likely to be released by anglers into
Maryland’s aquatic and terrestrial ecosystems. Many
of these species have the potential to become estab-
lished in the state. These results illustrate the need for
greater oversight of the bait industry, development of
consistent regulations on bait use, and a region-wide
education campaign aimed at changing anglers’
behavior regarding bait use and its disposal. We
recommend specific management actions that, if
implemented, would greatly reduce further bait-bucket
introductions and provide protection against invasive
bait species in Maryland and the Mid-Atlantic region.
Keywords Invasive species Bait Industry
Mid-Atlantic Angler behavior Vector
Anglers’ use of live bait contributes to the dispersal
of aquatic organisms throughout the United States
J. V. Kilian (&)R. J. Klauda M. Kashiwagi
R. Bourquin S. Weglein J. Schuster
Maryland Department of Natural Resources, Resource
Assessment Service, 580 Taylor Avenue C-2, Annapolis,
MD 21401, USA
S. Widman
Maryland Department of Natural Resources, Fisheries
Service, 580 Taylor Avenue C-2, Annapolis, MD 21401,
Biol Invasions (2012) 14:1469–1481
DOI 10.1007/s10530-012-0173-5
Author's personal copy
(Ludwig and Leitch 1996). Live bait either purchased
or harvested from the wild is often released into
drainage basins where it did not originate (Litvak and
Mandrak 1993). Consequently, many fishes, crayfish-
es, and other invertebrates used as bait have become
established in aquatic and terrestrial ecosystems
outside of their native ranges (Hobbs et al. 1989;
Fuller et al. 1999; Keller et al. 2007; Picco and Collins
2008). The import and use of live bait is also
responsible for the introduction of pathogens and
other non-bait organisms harbored within water or
packing material in live bait containers (Goodchild
2000). Bait-related introductions can result in estab-
lished populations of species which alter chemical and
physical processes and trophic structure of aquatic and
terrestrial ecosystems, in other words, invasive spe-
cies (Olsen et al. 1991; Charlebois and Lamberti 1996;
Goodchild 2000; Callaham Jr. et al. 2006; Migge-
Kleian et al. 2006). As well as effecting major
systemic changes in ecosystems, invasive bait species
are linked to the decline or elimination of native
species through hybridization, competition, predation,
habitat alteration, and other mechanisms (Moyle
1976; Stauffer 1984; Deacon 1988; Bestgen et al.
1989; Hobbs et al. 1989; Goodchild 2000; Tyus and
Saunders 2000; Wilson et al. 2004; Migge-Kleian
et al. 2006; Taylor et al. 2007).
Live bait use is responsible for the introduction of
47 known freshwater species in Mid-Atlantic slope
drainages; more than all other live trades combined
(P. Fuller, USGS, personal communication). Sus-
pected bait-bucket introductions of non-native species
are widespread in Maryland. The use of live bait is the
most likely vector responsible for the introductions of
at least five non-native fishes and four non-native
crayfishes. At least nine non-native earthworm spe-
cies, including several common bait species, are also
established in Maryland (Szlavecz and Csuzdi 2007).
The establishment of non-native species in Mary-
land resulting from bait-bucket introductions has been
followed by declines in native biodiversity. For
example, the non-native crayfish Orconectes virilis
(Virile Crayfish),first reported from the Patapsco
River in 1960 (Meredith and Schwartz 1960), was
subsequently transferred and introduced by anglers
into other watersheds and by 1997 was widespread in
streams, rivers, and reservoirs in central and western
Maryland (Kilian et al. 2010a). Declines of native
crayfishes in these regions followed, resulting in
extirpation of some natives from entire watersheds
(Schwartz et al. 1963; Kilian et al. 2010a).
The widespread distribution of Virile Crayfish and
recent discoveries of new invaders such as O. rusticus
(Rusty Crayfish; Kilian and Ashton 2007) indicate that
the sale and use of live bait remains a vector of non-
native, potentially invasive animals in Maryland, and
connected waters in surrounding states. Several
established invasive bait species (e.g., Rusty Crayfish)
are poised to be spread by anglers into other Maryland
watersheds and perhaps beyond. There is potential for
other non-native species not yet in Maryland to enter
the state as part of the live bait trade. Introduction of
these species may have future ecological and eco-
nomic repercussions.
Understanding the sources, sale and use of live bait
is crucial to developing sound policy on invasive
species (Keller and Lodge 2007), focusing regulations
effectively, and targeting public education efforts to
reduce bait-related introductions. Therefore, we con-
ducted a telephone survey of bait shops and a mail
survey of licensed anglers in 2008 to obtain information
on the sale, use, and disposition of live bait (hereafter
referred to as ‘‘bait’’) in Maryland. The objectives of
these surveys were to: (1) determine the major types
and sources of bait sold in bait shops; (2) quantify the
number of anglers using bait; (3) identify the major
types and sources of bait used by anglers; and (4)
quantify the percent of anglers releasing unused bait.
This is the first and most comprehensive examination of
the bait industry and the use of bait by anglers as a
vector of non-native and potentially invasive species in
Maryland, and, to our knowledge, the Mid-Atlantic
region. We present our survey results and recommend
specific actions needed to minimize the risk of future
bait-bucket introductions of invasive species.
Telephone survey of Maryland bait shops
We compiled a list of 116 Maryland bait and fishing
tackle shops from the Internet and telephone directo-
ries. Since we could not survey every store potentially
selling bait in Maryland, we surveyed only small,
locally-owned businesses and excluded convenience
and sporting goods stores and vending machines from
our sample. From October 15 to October 31, 2008,
1470 J. V. Kilian et al.
Author's personal copy
Maryland Department of Natural Resources (MDNR)
personnel made attempts to contact all 116 shops. In
some cases, repeated call backs were necessary. The
owners or managers of each bait shop contacted were
surveyed using a set script of six questions (Table 1).
These questions addressed the types of bait sold by
category, the source of each bait type, and the top-
selling bait items. We recorded all bait types as
reported by each bait shop owner or manager.
To document native and non-native species sold as
bait in Maryland, we visited and purchased specimens
from 17 bait shops. Twelve bait shops were randomly
selected, three from each of the four MDNR manage-
ment regions, in order to obtain a spatially represen-
tative sample of bait sold across the state. Due to
extensive problems with invasive crayfishes and
Carcinus maenas (Green Crab) in Maryland and
adjacent states, we also visited five bait shops
reportedly selling these bait types in order to obtain
information on these invasive animals. All 17 shops
were visited within a two-week period in May 2009.
We purchased samples of fishes, earthworms, crayf-
ishes, and crabs. These bait types were chosen because
of their known invasiveness in the Mid-Atlantic or
other regions. All specimens were preserved in either
10% buffered formalin or 70% ethanol and identified
to species level.
Summary statistics and graphics were generated
using Microsoft Excel. Responses were summarized
and are presented by major bait type category.
Mail survey of Maryland anglers
A total of 157,118 anglers purchased a Maryland
freshwater fishing license in 2008. Their names and
addresses were maintained in a database by the
MDNR Fisheries Service. From this database, we
selected a random sample of 10,000 resident and non-
resident anglers who purchased short term (3- or
5-day) or full-year freshwater, non-tidal fishing
licenses. We stratified the selection of anglers using
25 strata to ensure that our sample was spatially
representative (i.e., anglers from all regions of Mary-
land as well as non-resident anglers were included).
The 25 strata included Maryland’s 23 counties,
Baltimore City, and one stratum of all non-resident
anglers combined (anglers from 41 states and Wash-
ington, DC). Our random sample consisted of approx-
imately 6% of licensed anglers from each stratum. In
addition to making our sample spatially-representa-
tive, the stratified, random design allowed us to
perform calculations across strata to estimate the total
numbers of anglers. These estimates were of interest to
Maryland fisheries managers. To estimate the total
number of anglers, we multiplied percent response to
our mail survey in each stratum by the total number of
anglers in each stratum. Herein we present only the
extrapolated estimate for total number of anglers using
live bait. Other extrapolated estimates of anglers to
each survey question can be found in Kilian et al.
All 10,000 anglers were mailed a cover letter,
survey form, and postage-paid return envelope in
December 2008. Each survey form was individually
coded to facilitate tracking of responses by stratum.
The survey form included seven questions that
addressed the: (1) type of bait used and frequency of
use; (2) source of bait; (3) locations where bait was
used; and (4) disposal of unused bait (Table 2). Most
of the survey form consisted of multiple choice
Table 1 Questions asked of bait shop owners/managers by MDNR callers during the 2008 telephone survey
Initial survey question Follow-up questions
Do you sell live bait?
What types of live bait do you currently sell? Of the bait types you just mentioned, what is your top-selling
Do you purchase live bait from a wholesale distributor? If yes, what bait types do you purchase from distributors?
What distributors do you use?
Do you purchase live bait from local collectors? If yes, what bait types do you purchase from local collectors?
Do you collect bait yourself for your sales and for other
If yes, what bait types do you collect?
Do you purchase live bait from the Internet? If yes, what bait types do you purchase from Internet?
What websites do you use?
An assessment of a bait industry 1471
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questions. Anglers could provide more than one
answer for each question. Potential answers were
categorized by major bait type modified from Keller
et al. (2007). Categories included:
Minnows- Shiners
Anglers using bait that did not fit into one of these
categories were asked to describe the ‘‘other’’ bait type
used and were provided with an ‘‘other’’ category to
answer questions regarding source, location of use,
and disposal (Table 2).
All returned angler survey forms were entered into
a Microsoft Access database. We summed responses
from all 25 strata and calculated percent response
(total number of responses/total number surveyed) for
each survey question. In this paper, we present percent
response data for questions addressing bait use,
source, and disposal. Summary statistics and graphics
were generated using Microsoft Excel.
Table 2 Questions used in the mail survey of Maryland anglers. Survey responses to questions 5, 6, and 7 were subsequently
categorized by bait types listed in question 3
Survey question Multiple choice responses
(1) Do you ever fish with live bait in non-tidal freshwater? Yes
(2) List three non-tidal freshwater creeks, rivers, ponds, or lakes
where you have fished with live bait in the past 12 months
(3) If you use live bait in non-tidal, freshwater, what types do you use?
Please rank the types of bait you use from 1 to 5, with #1
representing the bait you most frequently use
a. Minnows-shiners
b. Earthworms-nightcrawlers
c. Crayfish
d. Grubs-mealworms-waxworms-maggots
e. Other type:_____________________
(4) What type of non-tidal freshwater areas do you typically fish? a. Creek
b. River
c. Small pond
d. Large lake or reservoir
e. Other
(5) If you use live bait, where do you get it? a. Catch my own
b. Bait/tackle shop
c. Internet
d. Convenience store
e. Vending machine
f. Other ______________________
(6) Where do you typically use live bait? a. Creek
b. River
c. Small pond
d. Large lake or reservoir
e. Other ___________________________
(7) At the end of the fishing trip, what do you do with your unused live
a. Release it live in the water
b. Dump it on shore
c. Save it for the next fishing trip
d. Place it in a trash can
e. Other ___________________________
1472 J. V. Kilian et al.
Author's personal copy
Telephone survey of Maryland bait shops
Seventy-two of 116 bait shops were successfully
contacted. The remaining 44 shops were either no
longer in business or we were unable to obtain their
current contact information. Seventy-one of the 72
contacted shops agreed to participate in our survey; 54
(76%) of these sold bait. In response to questions
regarding the type of bait sold, no bait shops reported
their bait types using scientific names nor in some
cases, even accepted common names (Table 3).
Worms were sold in fifty-one (94%) of the 54 shops
that sold bait. Twelve types of worms were reported
(Table 3). Nightcrawlers and bloodworms were the
most common types sold. Nineteen bait shops (35%)
Table 3 The types and sources of bait reported by Maryland bait shops
Number of shops
selling bait Type
Reported Sources of Bait
Local collector Self-caught Internet
Number Percent Number Percent Number Percent Number Percent
Worms Nightcrawlers 48 43 90 2 4 1 2 0 0
Trout worms 6 6 100 0 0 0 0 0 0
Nitro worms 1 1 100 0 0 0 0 0 0
Red wigglers 2 2 100 0 0 0 0 0 0
Green worms 4 4 100 0 0 0 0 0 0
Blood worms 41 37 90 0 0 0 0 0 0
Nuclear worms 1 1 100 0 0 0 0 0 0
Wax worms 11 10 91 0 0 0 0 0 0
Meal worms 17 17 100 0 0 0 0 0 0
Maggots 1 1 100 0 0 0 0 0 0
Butter worm 1 1 100 0 0 0 0 0 0
Leech 2 2 100 0 0 0 0 0 0
Fish Bull Minnow 20 11 55 6 30 6 30 0 0
Black salty 4 3 75 0 0 0 0 0 0
Fathead 10 10 100 0 0 0 0 0 0
Golden shiner 4 4 100 0 0 0 0 0 0
River herring 2 0 0 1 50 1 50 0 0
Eel 20 12 60 8 40 1 1 0 0
Crappie 1 1 100 0 0 0 0 0 0
Mullet 3 1 33 1 33 1 33 0 0
Spot 9 5 56 3 33 1 11 0 0
Unknown 12 9 75 5 42 2 17 0 0
Blue crab 18 5 28 14 78 3 17 0 0
Green crab 5 5 100 0 0 0 0 0 0
Mole crab 5 1 20 3 60 0 0 0 0
Grass shrimp 14 6 43 4 29 2 14 0 0
Crayfish Unknown 5 4 80 2 40 0 0 0 0
Percentages given are calculated using the number of shops reported selling each specific bait type (i.e., worms, fish, crabs/shrimp,
and crayfish)
The sum of percentages exceeds 100% for bait types for which multiple sources were reported
An assessment of a bait industry 1473
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reported that bloodworms were the top-selling of all
bait types.
Wholesale distributors were the largest source of
worms sold in bait shops (Table 3). Wholesale
distributors supplying worms to Maryland bait shops
were located in Maryland, Pennsylvania, New Jersey,
and Virginia. Two bait shops reported that they
obtained worms from local collectors. One bait shop
reported that they collected their own worms. The
Internet was not a source of worms sold in bait shops.
Five of the 12 types of worms reported from bait
shops during the telephone survey were varieties of
earthworm species, and were sold as nightcrawlers,
red wigglers, green worms, trout worms, and nitro
worms. During our visits to 17 bait shops, we
purchased earthworms sold as green nightcrawlers
and red worms. These types were not reported by bait
shops during the telephone survey. Earthworms sold
as bait included two genera and three species; all were
non-native. Lumbricus terristris were sold as night-
crawlers, green nightcrawlers, green worms, and nitro-
worms at 71% of shops visited. Lumbricus rubellus
were sold as red worms at 6% of shops and Eisenia
fetida were sold as red wigglers and trout worms at
24% of shops visited (Table 4).
Thirty-six bait shops (67%) sold fishes of nine types.
Twelve of the 36 bait shops could not identify the
species they sold. Bull minnows (i.e., Fundulus spp.)
and eels were the most common fishes sold. Twelve
bait shops (22%) reported that fishes were the top-
selling of all bait types.
Most fishes sold were purchased from wholesale
distributors (Table 3). Bull minnows, eels, river
herring, spot, and mullet were also obtained through
self-collection or purchased from local collectors. The
Internet was not a source of fishes sold in bait shops.
Fishes purchased from 17 bait shops included four
genera and five species. Non-native fishes included
Pimephales promelas (Fathead Minnow) and Caras-
sius auratus (Goldfish; Table 4). These species were
sold at 12 and 6% of shops visited, respectively.
Table 4 Species of worms, fishes, crayfishes, and crabs purchased by MDNR staff from 17 Maryland bait shops visited in May 2009
Category Genus/species Retail name Status in Maryland Percent of shops
selling species
Worms Lumbricus terrestris Nightcrawlers Non-native 71
Canadian nightcrawlers
Green nightcrawlers
Green worms
Lumbricus rubellus Red worms Non-native 6
Eisenia fetida Red wigglers Non-native 24
Trout worms
Fishes Carrasius auratus Black saltys Non-native 6
Pimephales promelas Fathead minnows Non-native 12
Notemigonus crysoleucas Golden shiners Native 24
Fundulus diaphanus Minnows Native 6
Fundulus heteroclitus Mummichogs Native 12
Bull minnows
Crayfishes Procambarus sp. (P. acutus or
P. zonangulus)
Crayfish Indeterminate 6
Crabs Carcinus maenas Green crab Non-native 6
Emerita talpoida Mole crab Native 6
Retail names are the names under which each species was sold
1474 J. V. Kilian et al.
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Twenty-eight bait shops (52%) sold crabs or shrimp
and reported four types; Blue Crab and Grass Shrimp
were the most common types. Only two (4%) of all
bait shops surveyed reported that crabs-shrimp were
the top-selling of all bait types. Callinectes sapidus
(Blue Crab) and Green Crab were the top-selling baits
in these two shops.
Nineteen of the 28 shops that sold crabs or shrimp
(68%) reported that they purchased Blue Crab, Grass
Shrimp, or Mole Crab from local collectors (Table 3).
Only four shops (14%) reported that they collected
their own blue crab or grass shrimp. Fourteen bait
shops (50%) purchased crabs or shrimp from whole-
sale distributors. Green crabs were purchased exclu-
sively from out-of-state wholesale distributors. The
Internet was not a source of crabs or shrimp sold in bait
Crab species purchased from the 17 bait shops we
visited included two genera and two species: the non-
native Green Crab and the native Emerita talpoida
(Mole Crab; Table 4). Although the native Blue Crab
was sold seasonally at the shops visited, it was not
available at the time of our survey.
Five bait shops (9%) reported selling crayfishes. None
of the shops could identify the crayfish species they
sold; most were sold by size as small, medium or large.
Crayfishes were not reported as a top-selling bait item
in any bait shops.
Four shops (80%) purchased crayfishes from
wholesale distributors (Table 3). Two shops (40%)
purchased crayfishes from local collectors. One shop
obtained crayfishes exclusively from local collectors.
The Internet was not a source of crayfishes in bait
Crayfishes were available at only one of the 17
shops visited during our survey. Other shops reported
that they could special order crayfishes upon request,
but did not keep crayfishes in stock. Specimens
purchased from this shop were identified as either
Procambarus acutus, a native species to Maryland, or
P. zonangulus, a non-native species (Table 4). Form I
male specimens used for species-level identification of
crayfishes were not available, prohibiting our ability to
differentiate between these two species.
Mail survey of Maryland anglers
Of 10,000 survey forms originally mailed, 764 were
returned as undeliverable. Of the 9,236 survey forms
successfully delivered, 2,237 survey forms were
completed and returned. Our adjusted response rate
was 24%. Response by stratum ranged from 14 to 33%
(mean response =24%). Sixty-four percent of sur-
veyed anglers reported that they used bait. Using
percent response and total number of anglers in each
stratum, we estimated that approximately 101,095
anglers use bait statewide in Maryland.
Types of bait used by anglers
The most common bait types used by freshwater
anglers were earthworms and fishes. Sixty-one percent
and 43% of surveyed anglers used earthworms and
fishes, respectively. Seventy-five percent and 33% of
anglers that used worms and fishes, respectively,
ranked these as their most frequently used bait.
Approximately 25% of anglers used grubs-meal-
worms-maggots and 20% of anglers used crayfishes.
Only 14 and 9% of anglers that used grubs and
crayfishes respectively, ranked these as their most
frequently used bait types. Approximately 11% of
anglers reported using ‘‘other’’ bait types. Twenty-
seven percent of anglers using ‘‘other’’ bait types
ranked it as their most frequently used bait. The most
commonly reported ‘‘other’’ bait types were hellgram-
mites, grass shrimp, and bloodworms, but also
included crickets, grasshoppers, insects, salamanders,
tadpoles, leeches, and other fishes.
Sources of bait to anglers
Bait shops were the most popular sources of fishes,
earthworms, grubs-mealworms-maggots, and ‘‘other’
bait types to anglers (Table 5). Anglers also obtained
earthworms, grubs-mealworms-maggots, and fishes
from other commercial sources, mostly convenience
stores and vending machines. Self-collection by
anglers was the most popular source of crayfishes,
and second most popular source of fishes, earthworms,
and ‘‘other’’ bait types. The Internet was a relatively
infrequent source of earthworms, grubs-mealworms-
maggots, and ‘‘other’’ bait types to anglers. It was not a
reported source of fishes and crayfishes. Other sources
An assessment of a bait industry 1475
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of bait reported by anglers were unnamed grocery
stores and large retail franchises such as Walmart.
Habitats where anglers use bait
Bait was used in all major aquatic freshwater habitats.
The majority of anglers used bait in rivers and
lakes, although grubs-mealworms-maggots were used
mostly in creeks and ponds (Table 5). The Chesapeake
and Ohio canal along the Potomac River was the only
‘other’’ freshwater location where anglers reported
using bait.
Dispostion of unused bait by anglers
The majority (65 and 69%, respectively) of anglers that
used fishes and crayfishes released their unused bait
into the water at the end of a fishing trip (Table 5).
Most anglers that used live earthworms, grubs-meal-
worms-maggots, and ‘‘other’’ bait types saved their
unused bait until the next fishing trip or released them
live into the water (Table 5). Approximately 18 and
10% of anglers released unused earthworms and grubs-
mealworms-maggots, respectively, live on shore. Nine
percent and 1% released unused earthworms and
grubs-mealworms-maggots, respectively, in their
home gardens, flower beds, or compost piles. Many
anglers reported giving unused bait of all types to other
anglers. ‘‘Other’ means of disposal included feeding
unused bait to pets.
Potential contribution of bait shops and wholesale
distributors to non-native species
Non-native and potentially invasive fishes (Litvak and
Mandrak 1993; LoVullo and Stauffer 1993; Ludwig
and Leitch 1996), crayfishes (DiStefano et al. 2009),
and earthworms (Keller et al. 2007) have been docu-
mented for sale in bait shops in other US states and
Canadian provinces/territories. Our survey confirmed
that the bait industry is a source of non-native and
invasive species in Maryland and likely to other states
in the region. We documented at least six non-native
bait species for sale in the state during our survey. Of
these, two worm species (L. terristris and L. rubellus),
Goldfish, and Green Crab, are invasive in other regions
(Deacon et al. 1964;McDonald et al. 2001; Walton et al.
Table 5 The source, location of use, and disposal of bait by Maryland freshwater anglers as determined by the mail survey
Category Minnows-shiners Earthworms-
Crayfish Grubs-mealworms-
Source Self-caught 40.8 45.9 72.6 10.9 57.8
Bait/tackle shop 75.1 60.8 24.5 71.3 57.0
Internet 0.0 0.2 0.0 1.6 0.8
Convenience store 11.7 44.4 1.8 31.2 19.8
Vending machine 0.3 1.7 0.0 0.9 0.4
Other source 0.5 4.3 0.5 3.9 8.0
Location of use Creek 28.7 40.7 30.2 44.6 42.6
River 55.9 57.1 59.0 38.5 76.8
Pond 28.5 45.8 24.5 41.8 39.7
Lake 57.3 53.6 43.3 41.9 46.4
Other 1.8 1.8 1.4 1.1 3.8
Disposal Release live in water 65.0 23.4 69.4 23.3 41.8
Release live on shore 3.3 17.8 2.5 9.5 0.0
Save for next trip 33.4 59.0 23.1 60.0 58.6
Place in trash can 8.7 10.9 4.1 15.2 16.9
Other 8.8 14.5 6.1 3.9 11.0
Values given are the percent response of anglers using each bait type
The sum of percentages of anglers exceeds 100% for questions to which multiple answers were given
1476 J. V. Kilian et al.
Author's personal copy
2002; Carlton and Cohen 2003; Hidalgo et al. 2005;
Rixon et al. 2005; Hendrix 2006; Keller et al. 2007).
Non-native invasive crayfishes (Virile Crayfish and
Procambarus clarkii Red Swamp Crawfish), not doc-
umented during this survey, were observed for sale in
Maryland bait shops as recently as 2006 (Kilian et al.
2010a). Our survey also confirmed that most bait sold in
shops originates from outside of the state, and in some
cases, outside the Mid-Atlantic region. Wholesale
distributors were the single largest source of all bait
types to Maryland bait shops. Bait shop owners
reported using a total of 24 wholesale distributors, 23
of which were located out-of-state. Although it is clear
from our survey that most bait originates from areas
outside of Maryland, the specific origins of both native
and non-native bait distributed by wholesalers to
Maryland bait shops are unknown. Some bait shops
reported that the earthworms (e.g., nightcrawlers) and
bloodworms they obtained from out-of-state wholesal-
ers were cultured or harvested in Canada and Maine,
respectively. The origins of fishes, crayfishes, crabs,
and shrimp imported by wholesalers remain unknown.
The list of non-native and invasive species that we
generated from specimens purchased and identified
during our survey is not comprehensive. Since we did
not purchase bait from all 72 bait shops for species-
level identification nor did we survey convenience
stores, large retail outlets, or vending machines as part
of this survey, it is possible that other non-native and
potentially invasive species not documented here are
also sold in the state as bait. Similarly, we may have
been unable to detect additional non-native species
due to temporal variation in what is available in bait
shops. Some bait species are only seasonally available
to anglers, and may not have been carried by bait shops
at the time of our visit.
Potential contribution of anglers to species
introductions and dispersal
Risks posed by the import of non-native bait species
would be reduced if all Maryland anglers were aware
of and followed current regulations prohibiting the
release (stocking) of animals into Maryland waters
without a permit. Results of our angler survey indicate
that (1) bait shops are the largest source of most bait
types to Maryland anglers, and (2) a large proportion
of anglers, both resident and non-resident, currently
release unused bait of many types and such release
occurs statewide. Thus, any non-native, potentially
invasive species imported into the state via the bait
industry is likely to be released by anglers into
Maryland’s aquatic and terrestrial ecosystems. The
potential for ecological damage caused by anglers’
release of bait is not limited to non-native species
alone. Native bait species (e.g., Golden Shiner,
Mummichog) cultured or harvested outside of the
state and imported by wholesale distributors have the
potential to introduce disease and alter native gene
pools (Philipp 1991; Litvak and Mandrak 2000).
The release of unused bait by anglers varied with
bait type. Anglers more readily released aquatic than
terrestrial bait types, which tend to be easier to store
for later use. For example, 65 and 69% of Maryland
anglers using fishes and crayfishes released their
unused bait; whereas only 18 and 10% of anglers
released their unused earthworms and grubs-meal-
worms-maggots, respectively. Our estimate for the
release of fishes by Maryland anglers (65%) is higher
than the 41% reported in Ontario (Litvak and Mandrak
1993) and 36% reported in Wisconsin and Michigan
(Kulwicki et al. 2003). Our estimate of 18% of anglers
releasing earthworms is similar to that reported in the
Upper Midwest (Keller et al. 2007).
Many anglers believe the release of bait is benefi-
cial to the recipient ecosystem (Litvak and Mandrak
1993). Based on comments provided by anglers on our
survey form, some anglers also believe their actions
are humane and that the release of unused bait benefits
game fish populations. Most Maryland freshwater
anglers appear to be unaware of, or choose to ignore,
the current regulation prohibiting the release of live
animals into Maryland waters. Although our survey
focused on freshwater anglers, it is likely that saltwa-
ter anglers also readily release unused bait into
Maryland’s tidal waters. Further surveys of saltwater
anglers of the Mid-Atlantic region are needed to
examine angler behavior as it relates to bait use in tidal
waters of Maryland and surrounding states.
Recommendations for reducing the threat of bait
bucket introductions
In recognition of the threat posed by bait-bucket
introductions, many US states and Canadian prov-
inces/territories have restricted the use, sale, or
transport of bait in some way (Litvak and Mandrak
1993,2000; Meronek et al. 1995; Kerr et al. 2005;
An assessment of a bait industry 1477
Author's personal copy
Peters and Lodge 2009). In their review of seven
Canadian provinces and 43 US states, Litvak and
Mandrak (2000) acknowledged that the number of bait
restrictions have increased among jurisdictions in
recent decades, but reported that many jurisdictions do
not address the import of bait in their regulations.
Jurisdictions that do regulate the import of bait have
tended to focus restrictions on individual species,
usually those that are known to be invasive (Peters and
Lodge 2009). Very few jurisdictions have prohibited
import of all non-native species (Meronek et al. 1995).
Although regulations focused on individual species
likely provide some amount of protection, this
approach fails to manage the live bait industry as the
broader vector (Peters and Lodge 2009). Oversight of
the bait industry, in the form of regulation, monitoring,
and enforcement varies widely among state and
Canadian provinces/territories (Litvak and Mandrak
1993,2000; Meronek et al. 1995; DiStefano et al.
2009; Peters and Lodge 2009).
In Maryland, the import, sale, possession, and use of
sixteen invasive aquatic animals, including four bait
species were banned as part of an Aquatic Nuisance
Species regulation in 2006 (COMAR 2006). The
banned bait species are Scardinius erythrophthalmus
(Rudd), Gymnocephalus cernuus Eurasian (Ruffe),
Neogobius melanostomus (Round Goby), and Rusty
Crayfish. Although bait was not the focus of this act,
this is the first and only regulation aimed at reducing the
import of invasive species by the bait industry in
Maryland. However, enforcement of this regulation is
minimal, limited largely by the lack of taxonomic
training for enforcement officers. Bait imports are not
routinely monitored in Maryland and current law does
not require wholesale and retail bait distributors to be
licensed or to register with MDNR. It is likely that there
are more wholesale distributors operating within
Maryland and the Mid-Atlantic region than those
identified in our survey. These distributors are not
required to keep records of sales or divulge their bait
species or sources. It is unlikely that most wholesale
distributors and retailers would be able to identify their
bait to species level (see DiStefano et al. 2009), which
is a significant regulatory impediment to prevention of
Preventing the import and sale of non-native,
invasive bait species requires greater oversight of the
bait industry through regulations, enforcement, edu-
cation, and monitoring. The need for such oversight is
reinforced by the dynamic nature of the bait industry,
where the sources and species of bait sold are likely to
change both within and among years (DiStefano et al.
2009), and projected growth in the international trade
of aquatic species (Levine and D’Antonio 2003;
Chang et al. 2009), in which new exotic and poten-
tially invasive species may enter the bait trade.
Management actions to improve oversight of the bait
industry and help prevent the import and sale of
invasive bait species in Maryland, other Mid-Atlantic
states, and any jurisdiction concerned about live bait
issues could include:
Require that wholesale and retail bait distributors
be licensed with state natural resource agencies
Require that retail bait shops provide annual
reports disclosing sources and types of bait sold
including names and locations of wholesale dis-
tributors from which they purchase
Require that wholesale distributors identify bait to
species level, keep records, and disclose sources
and species of bait
Educate all wholesale and retail distributors on
state regulations prohibiting the import and sale of
invasive species
Encourage retail bait shops and wholesale distrib-
utors to sell only native bait species
Provide taxonomic training of known invasive bait
species to enforcement officers and to bait shop
Improve enforcement of current state regulations
regarding prohibited invasive species by conduct-
ing periodic inspections of retail bait shops
Develop a ‘‘white list’’ of non-native species
deemed non-invasive that can be imported and
sold in bait shops
The implementation of these actions would
increase oversight of the bait industry and provide
data needed by state agencies to make informed
management decisions regarding the import and sale
of bait. These actions would also improve the ability
of state management agencies to target regulations
regarding invasive bait species appropriately and
effectively, disseminate educational and public out-
reach materials to both retail and wholesale distrib-
utors, and to enforce current and future regulations
involving bait species.
If implemented, the actions listed above would
likely reduce the import of invasive species into
1478 J. V. Kilian et al.
Author's personal copy
Maryland via the bait industry. However, the results of
our angler survey indicated that actions focused
entirely on the bait industry will not prevent additional
bait bucket introductions. Anglers reported that self-
collection was an important source of all bait types,
especially crayfish. Therefore, invasive bait species
already established in portions of the state are likely to
be spread into new areas via anglers’ bait buckets.
Efforts aimed at modifying angler behavior using a
combination of regulations and education are needed
to prevent the further spread of invasive species
already in the state.
Although many US states and Canadian provinces/
territories regulate the import of bait, only a few
states have banned the use of specific bait types
(Meronek et al. 1995; DiStefano et al. 2009). Follow-
ing widespread bait-bucket introductions of invasive
crayfishes, Wisconsin, Alberta, and Nova Scotia have
banned the use of all crayfishes as bait. Other states
and provinces have restricted their use to specified
areas (Lodge et al. 2000; DiStefano et al. 2009).
Maryland DNR recently banned the use and posses-
sion of crayfishes in three Maryland river basins that
contain the invasive Rusty Crayfish. This regulation
requires that all crayfishes collected for use as bait be
killed immediately upon capture and aims to prevent
the transport of Rusty Crayfish by anglers from these
rivers to other Maryland watersheds. Prevention of
bait-related introductions of invasive species would
be improved with regional collaboration among all
Mid-Atlantic States. Invasive species regulations in
Maryland, no matter how strict and well-enforced, are
only as good as the weakest regulations in states
sharing the Monongahela, Potomac, Susquehanna,
and Delaware rivers (Peters and Lodge 2009).
Regional bait dealers, anglers and management agen-
cies would benefit if regulations involving the import,
sale, and use of bait were developed in collaboration
and applied in a consistent manner across state
jurisdictions (Meronek et al. 1995; Peters and Lodge
2009). This would reduce confusion among anglers,
especially those who fish frequently as non-residents
in adjacent states, and would ease the enforcement of
bait regulations in shared water bodies. A regional
approach, as first suggested by Meronek et al. (1995)
and Peters and Lodge (2009), should be applied in the
Mid-Atlantic region to provide the highest level of
protection against bait-related introductions of inva-
sive species.
Kerr et al. (2005) opined that ‘‘since eradication of
an invasive species is seldom possible, prevention is
the key.’’ It is clear from our surveys that preventing
bait-bucket introductions requires substantial efforts
to increase awareness of invasive species issues within
the angling community and to educate anglers on how
to properly dispose of unused bait (Keller et al. 2007).
This requires development of a strategy that may
effectively employ social marketing techniques to
engage the angling community of Maryland and
surrounding states to increase their understanding
and alter their attitudes and behaviors regarding bait
use and disposal.
Acknowledgments We thank Jonathan McKnight, Tammy
O’Connell, Marek Topolski, Lisetta Silvestri, and Megan
Mueller for assistance with data collection and the MDNR
Invasive Species Matrix Team for providing assistance and
guidance with survey design and for support of this study. We
thank Arden Fields and Len Singel for assistance with the
MDNR Fisheries angler database. We also thank Dr. Paul
Hendrix of the University of Georgia for providing taxonomic
verifications of earthworm species and Zachary Loughman of
West Liberty University for crayfish identification. We thank
Scott Stranko, Kerrie Kyde, Jonathan McKnight, Robert
DiStefano, and two anonymous reviewers for providing
comments and suggestions that all led to improvements in the
manuscript. This study was funded in part by State Wildlife
Grant funds provided to the state wildlife agencies by US
Congress, and administered through the Maryland Department
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... Recreational fishing, most often through angling, involves catching animals that are not a primary source of food and that are not usually sold or traded (Arlinghaus et al. 2012). Anglers frequently use live fish as bait, and the majority discard any unused bait (Kilian et al. 2012). Many anglers erroneously believe that releasing bait is beneficial to ecosystems and game fish populations, despite the existence of prohibitory laws (Kilian et al. 2012, Drake & Mandrak 2014. ...
... Anglers frequently use live fish as bait, and the majority discard any unused bait (Kilian et al. 2012). Many anglers erroneously believe that releasing bait is beneficial to ecosystems and game fish populations, despite the existence of prohibitory laws (Kilian et al. 2012, Drake & Mandrak 2014. Therefore, bait release is an important pathway of introduction into areas where angling is common, with high reported rates of establishment (Gascho Landis et al. 2011). ...
... Indeed, baiting fish are either caught by anglers themselves or purchased from local retailers and then transported to a nearby angling site (Gascho Landis et al. 2011, Drake & Mandrak 2014. Second, the propagule pressure resulting from this pathway can be significant [e.g., in Maryland, USA, 65% of anglers using live fish as bait discarded any unused bait (Kilian et al. 2012)]. Recreational fishing is currently growing in popularity in some regions such as Central Europe (Lyach &Čech 2018), Brazil (Freire et al. 2012), and India (Gupta et al. 2015), and other developing countries will likely follow. ...
Freshwater fish have been widely introduced worldwide, and freshwater ecosystems are among those most affected by biological invasions. Consequently, freshwater fish invasions are one of the most documented invasions among animal taxa, with much information available about invasive species, their characteristics, invaded regions, invasion pathways, impacts, and management. While existing reviews address specific aspects of freshwater fish invasions, there is still a gaping lack of comprehensive assessments of freshwater fish invasions that simultaneously address pivotal and connected elements of the invasion process. Here, we provide a holistic review, together with quantitative assessments, divided into four major parts: ( a) introduction pathways, ( b) characteristics of nonnative species and invaded ecosystems that explain successful invasion processes, ( c) invasion impacts and their mechanisms, and ( d) management. We highlight data gaps and biases in the current databases and highlight a basic lack of understanding of several aspects of freshwater fish invasions. In addition, we provide recommendations for future studies. Expected final online publication date for the Annual Review of Ecology, Evolution, and Systematics, Volume 53 is November 2022. Please see for revised estimates.
... A potential use for the LAMP assay is to screen live bait for the presence of juvenile invasive carp, as contaminated live bait contributes to the introduction of aquatic invasive species throughout the United States and Canada [63,[94][95][96][97]. Minnows sold as live bait are often caught in the wild and held in holding ponds until distribution. ...
... Furthermore, surveys of anglers purchasing live bait in Ontario, Canada found that 41% of anglers said that they released leftover bait when they were done fishing and 56% responded that they were unaware that releasing live bait was illegal in the province [94]. Several states in the US have passed laws against the release of live bait, but Kilian et al. [96] found that 65% of anglers in Maryland released leftover live fish baits while 69% released leftover live crayfish used for bait. Our LAMP assay could be used to screen water from ponds used to raise live bait or from tanks containing live bait in bait shops as an initial screening tool to test for the presence of invasive carp. ...
Full-text available
Loop-mediated isothermal amplification (LAMP) is a rapid molecular detection technique that has been used as a diagnostic tool for detecting human and animal pathogens for over 20 years and is promising for detecting environmental DNA shed by invasive species. We designed a LAMP assay to detect the invasive carps, silver carp (Hypophthalmichthys molitrix), bighead carp (Hypophthalmichthys nobilis), black carp (Mylopharyngodon piceus), and grass carp (Ctenopharyngodon idella). To determine the sensitivity of the LAMP assay, we determined limit of detection (LOD) for each invasive carp species and compared with the performance of a grass carp quantitative PCR (qPCR) assay in LOD and in a mesocosm study. We used two grass carp densities, 3 juvenile grass carp in one mesocosm and 33 juvenile grass carp in the other. Prior to adding grass carp to the mesocosms, we added 68 kg of fathead minnows (Pimephales promelas) to each mesocosm to simulate farm ponds used for raising bait fish. We filtered 500 mL of water per sample to compare LAMP and qPCR analysis, and we collected 50 mL grab samples that were only analyzed using qPCR to gain additional data using a higher-throughput method to monitor environmental DNA (eDNA) levels throughout the study period. No eDNA for any of the four invasive carp species was detected in water collected from the mesocosms during the three days prior to adding grass carp. Forty-eight hours after grass carp addition to mesocosms, we detected grass carp eDNA in the mesocosm containing 33 grass carp using the LAMP assay. However, we failed to detect any grass carp DNA in the mesocosm containing 3 grass carp with the LAMP assay throughout the study. We analyzed the data using an occupancy model and found that the 500 mL filter samples yielded a higher eDNA capture probability than 50 mL grab samples in the mesocosm containing three grass carp but had similar eDNA capture probability in the mesocosm containing 33 grass carp. Both LAMP and qPCR reliably detected grass carp eDNA 2 days after grass carp addition, but detections were more consistent with qPCR. The LAMP assay may have utility for certain niche uses because it can be used to rapidly analyze eDNA samples and is robust to inhibition, despite having some limitations.
... While the legal use of live baitfish carries negligible risk of pathogen spread via incidental contact with hooked baitfish, the deliberate release of live, unused baitfish by anglers presents a more serious risk for aquatic invasive species and pathogen dispersal (Rodgers et al. 2011). As a result, baitfish release is prohibited in most states and provinces, but previous studies show that compliance is low and release rates range between 20% and 65% in studied populations (Litvak and Mandrak 1993;Kilian et al. 2012;Seekamp et al. 2016;Donnelly and Wolbers 2019). ...
... However, other studies have estimated much higher rates of baitfish release using similar mail survey methodology. For example, Kilian et al. 2012 reported that 65% of Maryland anglers release their live baitfish despite a prohibition on such behaviors in that state and hypothesized that anglers lacked awareness of relevant regulations. In Minnesota and some other states, it is likely that extensive angler education efforts (e.g., the "Clean Drain Dry Dispose" campaign) have boosted awareness of aquatic invasive species regulations among anglers (Jensen 2010;Cole et al. 2016;Seekamp et al. 2016), but differences in awareness are likely not able to fully explain release rates. ...
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The release of live baitfish by anglers has been identified as a high‐risk pathway for the introduction of aquatic invasive species due to the potential for invasive fish, invertebrates, or pathogens to be released simultaneously with the baitfish. Consequently, the release of live baitfish is illegal in many jurisdictions, but little is known about compliance rates or angler motivations for illegal release. To assess the incidence of live baitfish release in Minnesota, a state with significant live baitfish use and substantial recreational fisheries, we administered a mail survey to a random sample of 4,000 anglers who held a 2018–2019 annual fishing license and received 671 completed responses. To mitigate potential recall bias, we also administered 345 intercept surveys at water body access sites around the state to ask anglers about their current day’s behaviors. A total of 481 (72%) of the mail survey respondents reported that they used live baitfish, and of those, 98 (20%) reported that they release their leftover live baitfish into the water at least some of the time. Of the anglers surveyed at water body access sites, 59 (19%) were using live baitfish on the day they were surveyed, and of those, 11 (18%) released their leftover baitfish into the water. The reasons anglers provided for releasing their baitfish included convenience and their mistaken understanding that released baitfish benefit the recipient ecosystem. The potential for invasive species introductions through contaminated baitfish releases is high given the reported release rates. However, there is also significant opportunity for management interventions aimed at changing perceptions and providing convenient disposal alternatives to illegal release to reduce the risk presented by this pathway.
... While our model explicitly simulated extended spawning seasons, it also functionally assessed YOY habitat suitability across different introduction dates, regardless of how YOY become introduced. Therefore, introductions of live YOY by humans (e.g. release of live baitfish;Kilian et al., 2012) ...
Preventing invasive species establishment is a global conservation priority, yet limited management resources oftentimes restrict sites to target for prevention or monitoring. Risk assessments based on habitat suitability can identify sites most vulnerable to invasion that should be prioritized for preventative actions. Since habitat suitability is the result of interactions between environmental and organismal attributes, analyses should incorporate individual variability in demographics expected in an invasive population. Individual‐based models (IBM) can predict habitat suitability by accounting for interactions between environmental conditions and individual‐level variability. We developed an IBM to predict suitability of rivers in the northern U.S.A. to the invasive fishes silver carp (Hypophthalmichthys molitrix) and bighead carp (H. nobilis) and explored the projected effects of climate change on habitat suitability. All rivers supported adult survival, although complete survival of all adult demographics and positive growth only occurred in approximately 45% (17 of 38) of rivers for silver carp and 26% (10 of 38) of rivers for bighead carp. Only the largest individuals at the time of introduction survived in rivers where adult mortality occurred. Most rivers were unsuitable for young‐of‐year (89% and 92% of rivers for silver carp and bighead carp, respectively). Climate change simulations had relatively little effect on adult habitat suitability but resulted in up to four times the number of rivers being suitable for young‐of‐year by the late‐21st century and greatly extended the viable spawning season by up to an additional 65 days for silver carp and 77 days for bighead carp. Synthesis and applications. Our approach of using individual‐based models as a risk assessment tool informs proactive conservation planning by identifying sites for invasive species early detection monitoring, promoting the development of contingency response plans, and allowing for proactive prevention efforts. Model predictions also provide specific management guidance regarding the size and life stages to target for monitoring efforts, which capture gears to use, and the most effective time to sample for early detection monitoring.
... Catfish were ever stocked in Maine, they were first discovered in 1981 in a commercial bait tank within close proximity to the Penobscot River (USGS NAS 2022). The bait industry, along with boaters and anglers, are recognized as major vectors of aquatic invasive species (Kilian et al. 2012). While the introduction mechanism and timing is uncertain, it is clear that this species is nonnative and has been recently established within the Penobscot River watershed. ...
The Penobscot River Restoration Project was a large river rehabilitation project, culminating in the removal of the two lowermost dams (Veazie and Great Works) and improvements to fish passage on several remaining dams. Fish assemblages were surveyed for 3 years prior to rehabilitation, 3 years after, and now 8 years post-rehabilitation. Approximately 475 km of shoreline was sampled via boat electrofishing, yielding 133,394 individual fish of 41 species. The greatest shifts in assemblage structure occurred immediately after dam removal in formerly impounded sections, with increased prevalence of riverine and migratory species. Extended sampling documented several additional changes occurring within lower tributaries and tidally influenced river segments. Large schools of adult and young of the year alosines have increased in abundance upstream of the lowermost dam site although this area remains dominated by lacustrine species. Adult anadromous fishes continue to be in greatest abundance immediately below the Milford Dam. Our results provide continued evidence that dam removal results in fish assemblages dominated by riverine and anadromous species in previously impounded habitats, while upgraded fish passage has partially reconnected migratory species with historic habitat. While two new species were detected during the extended sampling effort, we observed an overall increase in the frequency of occurrence and spatial distribution of White Catfish (Ameiurus catus) within the lower portion of the Penobscot River. White Catfish have declined in their native range due to competition with introduced ictalurid catfish. Outside their native range, however, these fish have expanded their range northward along the Atlantic coast. White Catfish did not exist in Maine until recently. An introduction has allowed this species to establish in several coastal rivers in the state including the lower Penobscot River downstream of Milford Dam. Upstream access was gained following the two dam removals. Incorporation of a fish elevator at the third, Milford Dam, provides additional upstream access. Long-term boat electrofishing surveys revealed increases in the encounter rate for White Catfish (26%) coinciding with declines (45%) in the native Brown Bullhead, Ameiurus nebulosus. White Catfish are now poised to expand into habitat upstream of the dam. Electrofishing and baited trotline surveys demonstrated that the species is abundant within the tidally influenced freshwater, with one individual detected upstream of the Milford Dam. We compared age and growth via otoliths using fish captured at the Milford Dam and from the tidal reaches of river. Estimated growth parameters were consistent with populations from other Atlantic coastal rivers. Otolith cross sections were then analyzed for strontium and barium (Sr and Ba) using LA-ICP-MS to infer movements between fresh water and elevated salinities. We observed no notable changes of Sr or Ba, suggesting no discernable movements into elevated salinities. Together, these data suggest these fish have been established in the lower river, out competing brown bullhead where they co-occur and will likely continue impact the ecology of the upper Penobscot River as they continue to become establish.
... Despite the illegality of transporting and releasing bait fish in Ontario, it is highly likely that round goby were introduced into the Rideau Canal via a bait bucket release event. Although a population of round goby exists in Lake Ontario, it is unlikely that they naturally dispersed upstream through 14 lockstations undetected, and anglers have indeed been implicated as highly mobile invasion vectors (Keller and Lodge 2007;Bronnenhuber et al. 2011;Kilian et al. 2012;Drake and Mandrak 2014). Management and conservation efforts that promote public awareness, stewardship for the natural environment, and compliance to regulations should be pursued to reduce any additional unwanted introductions into new areas. ...
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The round goby (Neogobius melanostomus), native to the Black and Caspian Seas, is one of the most wide-ranging invasive fishes, having established in much of Europe and North America. In 2019, round goby were discovered to have colonized a central portion of the Rideau Canal, a 202 km historic waterway in Ontario, Canada. Round goby were found in low densities and had not been previously reported in any adjacent sections of the waterway, implying a newly-established source population. Passage through locks is the most likely means by which round goby can naturally disperse throughout the system, so modifying lock operations and infrastructure to minimize passages could reduce their spread. Additionally, understanding the range expansion and habitat preferences of pioneering individuals can help inform control efforts. We combined acoustic telemetry with hydraulic data to (1) characterize sex- and size-specific movements, (2) identify entry and exit pathways through a lock, and (3) assess dispersal rates and probability. We tracked 45 adult round goby downstream of Edmonds Lockstation during the navigation season from July to October, during which nine were detected inside the lock, with one fish successfully passing upstream. Most fish remained near the release site, though 26% of tagged individuals dispersed. The farthest distance a fish moved was 500 m (downstream) after 27 days, generating a maximum dispersal rate of 18.5 m/day. Although we lacked sufficient statistical power to detect size- or sex-specific movements, males were more commonly detected further from the release site. Our results suggest possible modifications to lock operations and infrastructure that managers could consider to reduce round goby expansion upstream from the invasion site.
... As P. clarkii is a main prey item for M. salmoides within the species natural distribution range in North America, art lure anglers were of the opinion that bass will grow bigger and faster if provided with its natural prey. This adds to the rising concern regarding the aquarium trade and recreational angling as major pathways for biological invasions (Chang et al. 2009;Kilian et al. 2012). Considering the extent of invasion and establishment in Mimosa Dam, the reservoir is now an incubator for further invasions (Havel et al. 2005). ...
This datasheet on Faxonius rusticus covers Identity, Overview, Distribution, Dispersal, Diagnosis, Biology & Ecology, Environmental Requirements, Natural Enemies, Impacts, Uses, Prevention/Control, Further Information.
1. The management of bio‐invasions relies upon the development of methods to trace their origin and expansion. Co‐introduced parasites, especially monogenean flatworms, are ideal tags for the movement of their hosts due to their short generations, direct life cycles and host specificity. However, they are yet to be applied to trace the intraspecific movement of host lineages in their native ranges. 2. As proof of this concept, we conducted a comparative phylogeographic analysis based upon two mitochondrial markers of a globally invasive frog Xenopus laevis and its monogenean parasite Protopolystoma xenopodis in its native range in southern Africa and invasive range in Europe. 3. Translocation of lineages was largely masked in the frog’s phylogeography. However, incongruent links between host and parasite phylogeography indicated host switches from one host lineage to another after these were brought into contact in the native range. Thus, past translocation of host lineages is revealed by the invasion success of its co‐introduced parasite lineage. 4. This study demonstrates that parasite data can serve as an independent line of evidence in invasion biology, also on the intraspecific level, shedding light on previously undetected invasion dynamics. Based upon the distribution of these invasive parasite lineages, we infer that there is widespread anthropogenic translocation of this frog, not only via official export routes, but also facilitated by the frog’s use as live bait by angling communities. 5. Synthesis and applications. Data from co‐introduced, host‐specific parasites, as tags for translocation, can add value to investigations in invasion biology and conservation. A better understanding of the translocation history and resulting genetic mixing of host and parasite lineages in the native range can shed light on the genetic make‐up of parasite assemblages co‐introduced to the invasive range. Knowledge of the intraspecific movement of different lineages of animals in their native ranges also has conservation implications, since contact between divergent lineages of hosts and parasites can facilitate host switches and altered parasite dynamics in both native and invasive populations. Therefore, we recommend the inclusion of parasite data as a more holistic approach to the invasion ecology of animals on the intraspecific level.
We used existing collection records to summarize the current understanding of freshwater crayfish diversity in Virginia. Virginia includes both Atlantic slope drainages and tributaries of the Tennessee and Ohio Rivers which flow to the Gulf of Mexico via the Mississippi River. The state’s varied topography produces a wide range of freshwater habitats from mountain-side springs and seeps to rushing mountain streams to warm, turbid rivers and the lentic habitats of the coastal plain. We report distributional patterns of 31 species and one subspecies. About 20% of the species reported are introduced, one native species is federally listed as threatened, and several other taxa are species of conservation concern. A number of yet-to-be-described taxa with highly limited distributions will likely need protection. We hope the data included will prove useful in future efforts to understand the diversity of these fascinating and ecologically important animals in Virginia and will further the resolution of Virginia’s complete crayfish fauna.
We compiled regulations on the bait industry in 1992 from 12 states in the north central United States: Illinois, Indiana, Iowa, Kansas, Michigan, Minnesota, Missouri, Nebraska, North Dakota, Ohio, South Dakota, and Wisconsin. Variation and inconsistency existed in the regulations among states. We believe anglers, management agencies, the bait industry, and the aquatic resource would benefit if states would review their bait regulations to attempt to reduce variation in regulations while maintaining regulations to protect and conserve aquatic resources.
Policy is used to prevent the introduction and spread of invasive species. For aquatic invasive species that can easily cross political boundaries, regional policies are needed. A weak link problem occurs when regulations of individual jurisdictions increase the region-wide risk of species introductions, especially in adjacent jurisdictions. Such cross-jurisdictional weak links may be compounded by another sort of weak link within jurisdictions: inconsistent regulation among multiple vectors that may introduce the same species. We used crayfish as a model system to study regulations for anglers, bait dealers, the pet trade, and aquaculture across the Great Lakes region. We identified a continuum of regulations ranging from no regulations to those that prohibit all use of crayfish. Furthermore, regulations differed depending on state and vector. Many states had regulations that specifically targeted the invasive rusty crayfish (Orconectes rusticus). However, these regulations were enacted reactively only after rusty crayfish had become established in the state. The lack of regulatory consistency among the Great Lakes jurisdictions is creating a multiple weak links problem and making success unlikely in efforts to slow the spread of crayfishes and other invasive species throughout the region.
We review eight different pathways for invasion by aquatic species into Ontario. These include fish stocking programs, private aquaculture, bait industry, aquarium and ornamental pond industry, live food fish industry, recreational boating, canals and diversions, and commercial shipping. These pathways have been responsible for the introduction of more than 160 invasive aquatic organisms into Ontario. Due to several gaps in policy and legislation, we conclude that the greatest potential pathways for the future introduction and spread of invasive aquatic species are associated with ballast water from the shipping industry, the live food fish industry, and the ornamental pond/aquarium trade. We offer recommendations to reduce the potential for establishment of additional invasive aquatic species. New legislation is required and public awareness programs need to be expanded. Response protocols need to be developed which clearly define roles and responsibilities of different agencies. Finally, a more coordinated effort between stakeholders and various levels of government with regard to invasive aquatic species is needed.
Les auteurs donnent un aperçu de l'introduction d'écrevisses exotiques à travers le monde depuis 1746. Les transplantations constatées par des documents ont une très large extension géographique et beaucoup d'autres n'ont sans doute jamais été signalées. Deux espèces d'origine nord-américaine ont été introduites avec un succès particulier: ce sont Orconectes rusticus, qui a été implanté en diverses régions des Etats-Unis et Procambarus clarkii, qui l'a été sur tous les continents, Antarctique et Australie exceptés. Dans la plupart des cas, quand ces espèces ont été établies, elles ont entraîné des changements drastiques dans la structure des communautés, avec le remplacement ou la réduction des populations d'écrevisses indigènes. Beaucoup de recherches sont nécessaires pour comprendre les mécanismes de remplacement des espèces (par exemple, exclusion compétitive, recrutement et croissance différentiels, subordination agressive) et leurs implications à long terme en ce qui concerne la structure des écosystèmes aquatiques. Les écrevisses exotiques fournissent certes de la nourriture pour l'Homme, mais les effets négatifs sont considérables et les transplantations extensives sont à décourager.
Crayfish are common inhabitants of North American streams and many species are undergoing human-assisted range expansions. We studied the effects of an introduced crayfish (Orconectes rusticus) on benthic macroinvertebrates and periphyton in a northern Michigan (USA) stream by 1) conducting a 46-d enclosure-exclosure experiment and 2) sampling benthic communities along a longitudinal gradient in crayfish density. In stream enclosures, crayfish reduced total macroinvertebrate densities by 47-58% and herbivore densities by 55-72% relative to exclosures. Over the course of the experiment, periphyton chlorophyll a increased by 48-70% in enclosures compared to an increase of only 8% in exclosures. Periphyton biomass, however, did not vary across treatments. Periphyton primary productivity increased 4-7 times in the presence of crayfish, probably because crayfish reduced grazer densities (indirect effect) and removed non-autotrophic components of the periphyton matrix (direct effect). The longitudinal survey supported experimental results. At sites along a crayfish density gradient occurring over 3 km of stream, periphyton chlorophyll a on rocks increased and macroinvertebrate density decreased with increasing crayfish density. These studies show that crayfish directly and indirectly affected the stream benthos, thereby producing responses at more than 1 trophic level. Some responses were consistent with a trophic cascade, but crayfish increased food web connectance by consuming periphyton. Therefore, crayfish can have complex, multi-trophic-level effects on the food webs of invaded streams.
A number of fishes have been introduced into the depauperate fish fauna of southern Nevada. Many of the introductions have had adverse effects on localized endemic species. Introduction of a cichlid and 5 poeciliids near Lake Mead seems to have resulted in elimination of a local race of Rhinichthys osculus; introduction of guppies at Preston endangers the resident population of Crenichthys baileyi; and introduction of goldfish at Manse Ranch threatens the remaining stock of Empetrichthys latos. Three of the introduced fishes, Cichlasoma nigrofasciatum, Lebistes reticulatus, and Mollienesia mexicana, do not seem to have been previously recorded to be established in the United States.