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About Turtle Survival Alliance
The Turtle Survival Alliance (TSA) was formed in 2001 as an International Union for Conservation of Nature (IUCN) partnership for sustainable captive management of freshwater turtles and tortoises, and initially designated a Task Force of the IUCN Tortoise and Freshwater Turtle Specialist Group. The TSA arose in response to the rampant and unsustainable harvest of Asian turtle populations to supply Chinese markets, a situation known as the Asian Turtle Crisis.
Since forming, the TSA has become recognized as a global force for turtle conservation, capable of taking swift and decisive action on behalf of critically endangered turtles and tortoises. Although the TSA was organized in response to the Asian Turtle Crisis, the group has been expanded as our understanding of the scope of turtle and tortoise declines has become better understood. The TSA has been particularly involved in recovery efforts where a managed breeding component is part of an overall survival strategy. The TSA employs a comprehensive strategy for evaluating the most critically endangered chelonians that identifies whether a species is prioritized for a captive program or through range country efforts, or a combination of both.
In the past 13 years, TSA secured nonprofit 501(c)(3) status (2005) and has centralized its base operations in South Carolina by opening the Turtle Survival Center (2013). The Turtle Survival Center, which now has AZA certification (2018), is home to a collection of more than 700 turtles and tortoises, representing 30 of the world’s critically endangered species. The TSA has also grown internationally, with significant field projects or programs in Madagascar, Myanmar and India, and additional projects in Belize, Colombia, and throughout Asia.
Today, the TSA is an action-oriented global partnership, focusing on species that are at high risk of extinction, and working in turtle diversity hotspots around the world. Widely recognized as a global catalyst for turtle conservation based on its reputation for swift and decisive action, the TSA has made a bold commitment to zero turtle extinctions in the 21st Century. The TSA is a recognized force for turtle conservation globally. TSA’s conservation actions utilize a three-pronged approach:
1. Restoring populations in the wild where possible;
2. Securing species in captivity through assurance colonies; and
3. Building the capacity to restore, secure and conserve species within their range country.
1
DRAFT – not for distribution
Position Statement on The Negative Effects of Maryland Style Crab Pots on Diamondback
Terrapin Populations and the Use of Bycatch Reduction Devices as a Practical, Inexpensive
Solution
Diamondback Terrapins are estuarine turtles whose range and habitat overlaps with the use of
“Maryland style” crab pots (2’x2’x2’ with funnel entries on two or all four sides) used widely in the
commercial and recreational harvest of blue crabs. Crab pots have been shown to substantially,
negatively affect terrapin populations in multiple states, and the bycatch problem with crab pots is
pervasive throughout the terrapin’s range along the Atlantic and Gulf coasts from Massachusetts to
Texas. In every study to date, a simple bycatch reduction device (BRD) has been shown to reduce
terrapin bycatch mortality in crab pots, with the net crab catch across all studies largely unchanged.
Therefore, it is the position of the Diamondback Terrapin Working Group (DTWG) that all commercial
and recreational “Maryland style” crab pots be fitted with a BRD on each entrance funnel into the crab
pot. Further, all states with commercial and recreational blue crab fisheries within the range of the
Diamondback Terrapin must have regulations requiring all Maryland style crab pots manufactured,
sold, or used within the state to be fitted with BRDs when fished. Finally, states should enforce BRD
compliance with routine checks of commercial and recreational crab pots when fished.
The Problem
The scientific literature documenting terrapin mortality in Maryland style blue crab pots and the
devastating impacts on terrapin populations is clear (reviewed by Chambers and Maerz, 2019). Bycatch
in Maryland style crab pots have been linked to declines of terrapin populations in New Jersey,
Maryland, Virginia, North Carolina, South Carolina, Georgia, and Florida. Terrapins enter Maryland
style crab pots and because they need to breath air, usually drown when they are entrapped underwater
for more than a few hours. Terrapin mortality in crab pots can impact populations by chronic drowning
of low numbers of terrapins in pots that are checked regularly and by the sporadic, mass mortality of
large numbers of terrapins in pots that are over-soaked, derelict, or lost (aka “ghost pots”).
94 dead Diamondback Terrapins in a derelict,
commercially fished Maryland style grab pot observed in
Glynn County, GA (see Grosse et al. 2009). 133 terrapins
were captured in this pot and an adjacent pot on five
occasions in 2007.
2
Misperceptions of the Problem
Several arguments have been put forward to discount the impact of Maryland style crab pots on terrapin
populations and downplay the need for bycatch reduction measures.
1. Chronic but low rates of bycatch mortality of terrapins throughout the crabbing season
indicates crabbing is benign.
This is false. Terrapin bycatch rates are generally less than one turtle per pot per day and vary
depending on the habitat, time of year, and the current size of the terrapin population in the
area. Because of their life history, we know that even small additions to terrapin mortality from
drowning in crab pots can result in population declines and prevent the slow recovery of terrapin
populations. The fishing of Maryland style crab pots in terrapin habitat can dramatically reduce
a terrapin population in as little as 5 years. Many terrapin populations have already been reduced
or extirpated by use of crab pots such that current observations by crabbers that they seldom or
never catch terrapins may already reflect the persistent legacy of crabbing bycatch.
2. Few terrapins are recovered during removal of derelict crab pots suggests that these pots do
not capture and kill many terrapins.
This is false. Reports of low terrapin bycatch in derelict crab pots are unreliable indicators of
the effect of Maryland crab pots on terrapin populations. Crab pot roundups or “rodeos”
generally occur during closed portions of the crabbing season, which are colder months when
terrapins are not active. Recent work has demonstrated that decomposition of terrapin carcasses
in crab pots is rapid (< 3 weeks). The only portions of the terrapin skeleton that may persist
within crab pots are very difficult to detect in a fouled crab pot and may only be identifiable by
individuals familiar with turtle anatomy.
Bycatch Reduction Devices Reduce Terrapin Entrapment in Crab Pots
Bycatch reduction devices are typically rectangular devices installed in the funnels of crab pots to alter
the dimensions of the funnel opening, thereby preventing terrapins from entering the crab pot. Terrapins
are primarily restricted by the height of the device. All published studies report some reduction of
terrapin bycatch with the installation of BRDs. Different sizes of BRDs have been evaluated in a variety
of states throughout the terrapin’s range (see Appendix Table 2). A 4.5 cm (1.75 inch) high BRD
reduces terrapin catch by 70-80% whereas a 5 cm (2 inch) high BRD can be less effective at reducing
terrapin catch (40-50%). The width of the BRD does not play a role in reducing terrapin capture and
thus can be variable. Other BRD designs or orientations may be feasible alternatives but need to be
evaluated to demonstrate their effectiveness.
Percent change in catch of Diamondback Terrapins and Blue
Crabs in crab pots with BRDs relative to crab pots without
BRDs. The vertical dashed line represents no change in catch
between pots with and without BRDs.
3
Bycatch Reduction Device Effects on Crab Catch
A large majority of BRD studies have shown that both the 4.5 and 5 cm BRDs have little if any effect
on numbers or sizes of crabs caught (see Appendix Tables 3 & 4). A few studies report reduced numbers
of crabs caught while others report higher numbers of crabs caught in pots with BRDs; but the average
effect of all these studies centers on no effect on the numbers of crabs caught. Some studies that report
lower numbers of crabs caught may have had the BRDs installed inappropriately on the outer face of
the funnel, which could discourage crabs from entering pots. Whether BRD placement explains the
occasional reduction in the numbers of crabs caught needs to be evaluated.
Recommended Installation, Use, and Enforcement of BRDs
BRD installation is an inexpensive and easy retrofit to existing crab pots. To minimize the potential for
reducing crab capture, we recommend installing the BRD on the inside end of the funnel. Installing the
BRD on the outside surface of the funnel will not affect terrapin exclusion, but crabs might sense the
obstruction while entering the funnel.
Left panel: Wire BRD installed as recommended at the back, inside margin of the funnel to maintain
its integrity. Right panel: Plastic BRD installed on the outer face of the funnel in a manner more likely
to affect crab catch
Although the habitat of Diamondback Terrapins and location of the blue crab fishery largely overlap,
some coastal environments that are far from shore are fished for blue crabs and have never been terrapin
habitat. Evidence from Georgia and North Carolina suggest that terrapins are particularly prone to
bycatch in crab pots set in smaller, shallower tidal creeks. The softshell “peeler” crab fishery may be
particularly prone to terrapin bycatch. New Jersey requires the use of BRDs only on crab pots fished
within 150 feet of shore, though this may not be a sufficient criteria for all states within the terrapin’s
range. BRD regulations could be tailored to require BRDs only in areas of overlap between commercial
and recreational crabbing with Maryland style crab pots and terrapin habitat. Of course, requiring the
use of BRDs on all Maryland style crab pots creates easier guidelines for compliance and enforcement.
Compulsory use of BRDs likewise would reduce the risk of terrapins drowning in pots originally placed
outside their habitat but accidentally blown into the nearshore as derelict pots.
Cost of BRDs Use and Non-Use
BRD costs vary based on the material and manufacturer but they can be homemade from ridged (9
gauge or less) galvanized wire. Plastic BRDs are commercially available from $0.45 -$1 each, and pots
require a BRD for each funnels, typically 2 or 4. Range-wide implementation of BRDs or state
4
regulations to require that BRDs be installed on any pots sold within the state would likely result in the
manufacture of crab pots with BRDs pre-installed.
Recent watchlists now advocate complete avoidance of purchasing blue crab harvested from states
where BRDs are not required and unsustainable deaths of terrapins from the crab fisheries are
documented. For example, the Monterey Bay Seafood Watch currently recommends avoiding blue
crabs from Virginia, North Carolina, South Carolina, Georgia, Florida, Mississippi, Louisiana and
Texas because regulations to protect terrapins have not been implemented (www.seafoodwatch.org).
The small cost of adoption of BRDs is likely to be dwarfed by increased calls for boycotts of blue crab
harvested in states without BRD regulations.
Position of the Diamondback Terrapin Working Group
The Diamondback Terrapin Working Group was formed in 2004 by individuals from academic,
scientific, regulatory and private institutions/organizations working to promote the conservation of the
Diamondback Terrapin, the preservation of intact, wild terrapin populations and their associated
ecosystems throughout their range. The Diamondback Terrapin Working Group is committed to and
supports research, management, conservation, and education efforts with the above goals in mind. The
Diamondback Terrapin Working Group calls for regulations requiring the use of Bycatch Reduction
Devices (BRDs) in “Maryland style” crab pots throughout the terrapin’s range. The position of the
working group is that the scientific data are abundant and clear that commercial and recreational use
of Maryland style crab pots is a primary threat to the conservation of Diamondback Terrapins
throughout the species range, and that BRDs effectively reduce terrapin capture and mortality with
minimal effect on crab catch. State agencies throughout the terrapin’s range or federal authorities
should require the adoption of BRDs.
Diamondback Terrapin Working Group Position Statement Signatories
Willem Roosenburg, Ph.D. – Ohio Center for Ecology and Evolutionary Studies, Ohio University
John C. Maerz, Ph.D. – Warnell School of Forestry and Natural Resource, University of Georgia
Randy Chambers, Ph.D. – Keck Environmental Lab, William & Mary
Amanda Southwood Williard, Ph.D. – Department of Biology and Marine Biology, University of North
Carolina Wilmington
5
Appendix
Table 1. Catch rates of terrapins in Crab Pots
State and Study
CPUE terrapins* crab pot-1
day-1
South Carolina (Bishop 1983)
South Carolina (Hoyle and
Gibbons 2000)
0.16 -0.24
0.027
North Carolina (Grant 1997)
North Carolina (Hart and
Crowder 2011)
0.15
0.003 – 0.008
Maryland (Roosenburg et al.
1997)
Maryland (Roosenburg and
Green 2000)
Maryland (Jenkins and
Roosenburg unpub)
0.17
0.044-0.23
0.19
New Jersey (Wood, 1997a,
1997b)
0.071 -0.49
Alabama (Coleman et al.
2015)
0.0125
Florida ( Butler and Heinrich
2007)
0.0 – 0.147
Virginia (Upperman et al.
2014 )
Virginia (Rook et al. 2010)
0.295
0.201
Texas (Baxter 2013)
1.15
Georgia (Belcher et al 2008)
0.60 – 1.15 /soak
6
Table 2. Effectiveness of BRDs at eliminating terrapin capture in crab pots
State
BRD
Type
Dimensions
(cm)
Terrapin Bycatch
Control:BRD
Alabama
Wire
5x15
22:2
Delaware
Wire
5x10
97:40
Delaware
Wire
3.8x12
106:0
Delaware
Wire
4.5x12
106:36
Delaware
Wire
5x12
106:93
Florida
Wire
4.5x12
37:4
Georgia
Plastic
5x15
136:5
Louisiana
Wire
5x10
0:0
Maryland
N/A
4.5x12
1:0
Maryland
Wire
4.5x12
105:19
Maryland
Wire
5x10
105:56
Maryland
Plastic
4.5x12
41:6
Mississippi
Wire
5x15
0:0
Mississippi
Wire
5x10
0:0
New Jersey
Wire
5x10
40:3
New Jersey
Wire
4.5x10
3:0
New Jersey
Wire
5x10
25:4
New Jersey
Wire
5x10
46:5
North Carolina
Wire
4x15; 5x15
13:1
North Carolina
Wire
5x16
7:0
North Carolina
Wire
4x16; 4.5x16
1:0
South Carolina
Plastic
5x15
30:0
South Carolina
Plastic
4.5x12
75:3
Texas
Plastic
4.5x12
2:0
Virginia
Plastic
4.5x12
2:0
Virginia
Plastic
4.5x12
69:2
7
Virginia
Plastic
5x15
69:0
Virginia
Plastic
4.5x12
9:0
Virginia
Plastic
4.5x12
42:0
Virginia
Plastic
4.5x12
46:2
Virginia
Plastic
5x15
58:10
Virginia
Plastic
5x15
23:6
8
Table 3. Effect of 4.5 cm high BRD on Crab Catch.
State
BRD
Type
Dimensions
(cm)
Change in
Crab Size
Change in
Crab Number
Reference
Delaware Wire
4.5x12
No Change
~14% Decrease
Cole and Helser 2001
Florida
Wire
4.5x12
No Change
No Change
Butler and Heinrich 2007
Maryland N/A
4.5x12
N/A
29% Decrease
Lukacovic et al. 2005
Maryland Wire
4.5x12
No Change
No Change
Roosenburg and Green
2000
Maryland
Plastic 4.5x12
No Change
No Change
Jenkins and Roosenburg
2018
New Jersey Wire
4.5x10
No Change
12% Increase
Wood 1997
North
Carolina
Wire
4x16;
4.5x16
N/A
23% Decrease
Hart and Crowder 2011
South
Carolina
Plastic 4.5x12
N/A
21% Decrease
Powers et al. 2009
Texas
Plastic 4.5x12
No Change
No Change
Baxter 2014
Virginia
Plastic 4.5x12
Slight
Decrease
~25% Increase
R. Lipcius, VIMS, pers.
comm.
Virginia
Plastic 4.5x12
No Change
53% Decrease
Upperman et al. 2014
Virginia
Plastic 4.5x12
N/A
17% Decrease
Morris et al. 2011
Virginia
Plastic 4.5x12
N/A
47% Decrease
Morris et al. 2011
Virginia
Plastic 4.5x12
No Change
No Change
Rook et al. 2010
9
Table 4. Effect of 5 cm high BRD on crab catch
State
BRD
Type
Dimensions
(cm)
Change in
Crab Size
Change in
Crab Number
Reference
Alabama
Wire
5x15
N/A
31% Decrease
Coleman et al. 2011
Delaware
Wire
5x10
No Change
No Change
Cole and Helser 2001
Delaware
Wire
5x12
No Change
No Change
Cole and Helser 2001
Georgia
Plastic
5x15
No Change
~14% Decrease Belcher et al. 2007
Louisiana
Wire
5x10
N/A
38% Increase
Guillory and Prejean
1998
Maryland
Wire
5x10
No Change
No Change
Roosenburg and Green
2000
Mississippi Wire
5x15
No Change
No Change
Graham et al. 2011
Mississippi Wire
5x10
No Change
No Change
Cuevas et al. 2000
New Jersey Wire
5x10
No Change
No Change
Mazzarella 1994
New Jersey
Wire
5x10
No Change
10% Increase
Wood 1997
New Jersey Wire
5x10
No Change
49% Increase
Wood 1997
North
Carolina
Wire
4x15; 5x15
No Change
No Change
Chavez 2014
North
Carolina
Wire
5x16
N/A
No Change
Hart and Crowder
2011
North
Carolina
Wire
5x15
No Change
12% Decrease
Chavez and Williard
2017
South
Carolina
Plastic
5x15
N/A
N/A
Powers et al. 2009
Virginia
Plastic
5x15
No Change
No Change
Upperman et al. 2014
Virginia
Plastic
5x15
Slight
Decrease
No Change
Corso et al. 2017
Virginia
Plastic
5x15
Slight
Increase
No Change
Grubbs et al. 2018
DRAFT – not for distribution
Position Statement on The Negative Effects of Maryland Style Crab Pots on Diamondback
Terrapin Populations and the Use of Bycatch Reduction Devices as a Practical, Inexpensive
Solution
Diamondback Terrapins are estuarine turtles whose range and habitat overlaps with the use of
“Maryland style” crab pots (2’x2’x2’ with funnel entries on two or all four sides) used widely in the
commercial and recreational harvest of blue crabs. Crab pots have been shown to substantially,
negatively affect terrapin populations in multiple states, and the bycatch problem with crab pots is
pervasive throughout the terrapin’s range along the Atlantic and Gulf coasts from Massachusetts to
Texas. In every study to date, a simple bycatch reduction device (BRD) has been shown to reduce
terrapin bycatch mortality in crab pots, with the net crab catch across all studies largely unchanged.
Therefore, it is the position of the Diamondback Terrapin Working Group (DTWG) that all commercial
and recreational “Maryland style” crab pots be fitted with a BRD on each entrance funnel into the crab
pot. Further, all states with commercial and recreational blue crab fisheries within the range of the
Diamondback Terrapin must have regulations requiring all Maryland style crab pots manufactured,
sold, or used within the state to be fitted with BRDs when fished. Finally, states should enforce BRD
compliance with routine checks of commercial and recreational crab pots when fished.
The Problem
The scientific literature documenting terrapin mortality in Maryland style blue crab pots and the
devastating impacts on terrapin populations is clear (reviewed by Chambers and Maerz, 2019). Bycatch
in Maryland style crab pots have been linked to declines of terrapin populations in New Jersey,
Maryland, Virginia, North Carolina, South Carolina, Georgia, and Florida. Terrapins enter Maryland
style crab pots and because they need to breath air, usually drown when they are entrapped underwater
for more than a few hours. Terrapin mortality in crab pots can impact populations by chronic drowning
of low numbers of terrapins in pots that are checked regularly and by the sporadic, mass mortality of
large numbers of terrapins in pots that are over-soaked, derelict, or lost (aka “ghost pots”).
94 dead Diamondback Terrapins in a derelict,
commercially fished Maryland style grab pot observed in
Glynn County, GA (see Grosse et al. 2009). 133 terrapins
were captured in this pot and an adjacent pot on five
occasions in 2007.
2
Misperceptions of the Problem
Several arguments have been put forward to discount the impact of Maryland style crab pots on terrapin
populations and downplay the need for bycatch reduction measures.
1. Chronic but low rates of bycatch mortality of terrapins throughout the crabbing season
indicates crabbing is benign.
This is false. Terrapin bycatch rates are generally less than one turtle per pot per day and vary
depending on the habitat, time of year, and the current size of the terrapin population in the
area. Because of their life history, we know that even small additions to terrapin mortality from
drowning in crab pots can result in population declines and prevent the slow recovery of terrapin
populations. The fishing of Maryland style crab pots in terrapin habitat can dramatically reduce
a terrapin population in as little as 5 years. Many terrapin populations have already been reduced
or extirpated by use of crab pots such that current observations by crabbers that they seldom or
never catch terrapins may already reflect the persistent legacy of crabbing bycatch.
2. Few terrapins are recovered during removal of derelict crab pots suggests that these pots do
not capture and kill many terrapins.
This is false. Reports of low terrapin bycatch in derelict crab pots are unreliable indicators of
the effect of Maryland crab pots on terrapin populations. Crab pot roundups or “rodeos”
generally occur during closed portions of the crabbing season, which are colder months when
terrapins are not active. Recent work has demonstrated that decomposition of terrapin carcasses
in crab pots is rapid (< 3 weeks). The only portions of the terrapin skeleton that may persist
within crab pots are very difficult to detect in a fouled crab pot and may only be identifiable by
individuals familiar with turtle anatomy.
Bycatch Reduction Devices Reduce Terrapin Entrapment in Crab Pots
Bycatch reduction devices are typically rectangular devices installed in the funnels of crab pots to alter
the dimensions of the funnel opening, thereby preventing terrapins from entering the crab pot. Terrapins
are primarily restricted by the height of the device. All published studies report some reduction of
terrapin bycatch with the installation of BRDs. Different sizes of BRDs have been evaluated in a variety
of states throughout the terrapin’s range (see Appendix Table 2). A 4.5 cm (1.75 inch) high BRD
reduces terrapin catch by 70-80% whereas a 5 cm (2 inch) high BRD can be less effective at reducing
terrapin catch (40-50%). The width of the BRD does not play a role in reducing terrapin capture and
thus can be variable. Other BRD designs or orientations may be feasible alternatives but need to be
evaluated to demonstrate their effectiveness.
Percent change in catch of Diamondback Terrapins and Blue
Crabs in crab pots with BRDs relative to crab pots without
BRDs. The vertical dashed line represents no change in catch
between pots with and without BRDs.
3
Bycatch Reduction Device Effects on Crab Catch
A large majority of BRD studies have shown that both the 4.5 and 5 cm BRDs have little if any effect
on numbers or sizes of crabs caught (see Appendix Tables 3 & 4). A few studies report reduced numbers
of crabs caught while others report higher numbers of crabs caught in pots with BRDs; but the average
effect of all these studies centers on no effect on the numbers of crabs caught. Some studies that report
lower numbers of crabs caught may have had the BRDs installed inappropriately on the outer face of
the funnel, which could discourage crabs from entering pots. Whether BRD placement explains the
occasional reduction in the numbers of crabs caught needs to be evaluated.
Recommended Installation, Use, and Enforcement of BRDs
BRD installation is an inexpensive and easy retrofit to existing crab pots. To minimize the potential for
reducing crab capture, we recommend installing the BRD on the inside end of the funnel. Installing the
BRD on the outside surface of the funnel will not affect terrapin exclusion, but crabs might sense the
obstruction while entering the funnel.
Left panel: Wire BRD installed as recommended at the back, inside margin of the funnel to maintain
its integrity. Right panel: Plastic BRD installed on the outer face of the funnel in a manner more likely
to affect crab catch
Although the habitat of Diamondback Terrapins and location of the blue crab fishery largely overlap,
some coastal environments that are far from shore are fished for blue crabs and have never been terrapin
habitat. Evidence from Georgia and North Carolina suggest that terrapins are particularly prone to
bycatch in crab pots set in smaller, shallower tidal creeks. The softshell “peeler” crab fishery may be
particularly prone to terrapin bycatch. New Jersey requires the use of BRDs only on crab pots fished
within 150 feet of shore, though this may not be a sufficient criteria for all states within the terrapin’s
range. BRD regulations could be tailored to require BRDs only in areas of overlap between commercial
and recreational crabbing with Maryland style crab pots and terrapin habitat. Of course, requiring the
use of BRDs on all Maryland style crab pots creates easier guidelines for compliance and enforcement.
Compulsory use of BRDs likewise would reduce the risk of terrapins drowning in pots originally placed
outside their habitat but accidentally blown into the nearshore as derelict pots.
Cost of BRDs Use and Non-Use
BRD costs vary based on the material and manufacturer but they can be homemade from ridged (9
gauge or less) galvanized wire. Plastic BRDs are commercially available from $0.45 -$1 each, and pots
require a BRD for each funnels, typically 2 or 4. Range-wide implementation of BRDs or state
4
regulations to require that BRDs be installed on any pots sold within the state would likely result in the
manufacture of crab pots with BRDs pre-installed.
Recent watchlists now advocate complete avoidance of purchasing blue crab harvested from states
where BRDs are not required and unsustainable deaths of terrapins from the crab fisheries are
documented. For example, the Monterey Bay Seafood Watch currently recommends avoiding blue
crabs from Virginia, North Carolina, South Carolina, Georgia, Florida, Mississippi, Louisiana and
Texas because regulations to protect terrapins have not been implemented (www.seafoodwatch.org).
The small cost of adoption of BRDs is likely to be dwarfed by increased calls for boycotts of blue crab
harvested in states without BRD regulations.
Position of the Diamondback Terrapin Working Group
The Diamondback Terrapin Working Group was formed in 2004 by individuals from academic,
scientific, regulatory and private institutions/organizations working to promote the conservation of the
Diamondback Terrapin, the preservation of intact, wild terrapin populations and their associated
ecosystems throughout their range. The Diamondback Terrapin Working Group is committed to and
supports research, management, conservation, and education efforts with the above goals in mind. The
Diamondback Terrapin Working Group calls for regulations requiring the use of Bycatch Reduction
Devices (BRDs) in “Maryland style” crab pots throughout the terrapin’s range. The position of the
working group is that the scientific data are abundant and clear that commercial and recreational use
of Maryland style crab pots is a primary threat to the conservation of Diamondback Terrapins
throughout the species range, and that BRDs effectively reduce terrapin capture and mortality with
minimal effect on crab catch. State agencies throughout the terrapin’s range or federal authorities
should require the adoption of BRDs.
Diamondback Terrapin Working Group Position Statement Signatories
Willem Roosenburg, Ph.D. – Ohio Center for Ecology and Evolutionary Studies, Ohio University
John C. Maerz, Ph.D. – Warnell School of Forestry and Natural Resource, University of Georgia
Randy Chambers, Ph.D. – Keck Environmental Lab, William & Mary
Amanda Southwood Williard, Ph.D. – Department of Biology and Marine Biology, University of North
Carolina Wilmington
5
Appendix
Table 1. Catch rates of terrapins in Crab Pots
State and Study
CPUE terrapins* crab pot-1
day-1
South Carolina (Bishop 1983)
South Carolina (Hoyle and
Gibbons 2000)
0.16 -0.24
0.027
North Carolina (Grant 1997)
North Carolina (Hart and
Crowder 2011)
0.15
0.003 – 0.008
Maryland (Roosenburg et al.
1997)
Maryland (Roosenburg and
Green 2000)
Maryland (Jenkins and
Roosenburg unpub)
0.17
0.044-0.23
0.19
New Jersey (Wood, 1997a,
1997b)
0.071 -0.49
Alabama (Coleman et al.
2015)
0.0125
Florida ( Butler and Heinrich
2007)
0.0 – 0.147
Virginia (Upperman et al.
2014 )
Virginia (Rook et al. 2010)
0.295
0.201
Texas (Baxter 2013)
1.15
Georgia (Belcher et al 2008)
0.60 – 1.15 /soak
6
Table 2. Effectiveness of BRDs at eliminating terrapin capture in crab pots
State
BRD
Type
Dimensions
(cm)
Terrapin Bycatch
Control:BRD
Alabama
Wire
5x15
22:2
Delaware
Wire
5x10
97:40
Delaware
Wire
3.8x12
106:0
Delaware
Wire
4.5x12
106:36
Delaware
Wire
5x12
106:93
Florida
Wire
4.5x12
37:4
Georgia
Plastic
5x15
136:5
Louisiana
Wire
5x10
0:0
Maryland
N/A
4.5x12
1:0
Maryland
Wire
4.5x12
105:19
Maryland
Wire
5x10
105:56
Maryland
Plastic
4.5x12
41:6
Mississippi
Wire
5x15
0:0
Mississippi
Wire
5x10
0:0
New Jersey
Wire
5x10
40:3
New Jersey
Wire
4.5x10
3:0
New Jersey
Wire
5x10
25:4
New Jersey
Wire
5x10
46:5
North Carolina
Wire
4x15; 5x15
13:1
North Carolina
Wire
5x16
7:0
North Carolina
Wire
4x16; 4.5x16
1:0
South Carolina
Plastic
5x15
30:0
South Carolina
Plastic
4.5x12
75:3
Texas
Plastic
4.5x12
2:0
Virginia
Plastic
4.5x12
2:0
Virginia
Plastic
4.5x12
69:2
7
Virginia
Plastic
5x15
69:0
Virginia
Plastic
4.5x12
9:0
Virginia
Plastic
4.5x12
42:0
Virginia
Plastic
4.5x12
46:2
Virginia
Plastic
5x15
58:10
Virginia
Plastic
5x15
23:6
8
Table 3. Effect of 4.5 cm high BRD on Crab Catch.
State
BRD
Type
Dimensions
(cm)
Change in
Crab Size
Change in
Crab Number
Reference
Delaware Wire
4.5x12
No Change
~14% Decrease
Cole and Helser 2001
Florida
Wire
4.5x12
No Change
No Change
Butler and Heinrich 2007
Maryland N/A
4.5x12
N/A
29% Decrease
Lukacovic et al. 2005
Maryland Wire
4.5x12
No Change
No Change
Roosenburg and Green
2000
Maryland
Plastic 4.5x12
No Change
No Change
Jenkins and Roosenburg
2018
New Jersey Wire
4.5x10
No Change
12% Increase
Wood 1997
North
Carolina
Wire
4x16;
4.5x16
N/A
23% Decrease
Hart and Crowder 2011
South
Carolina
Plastic 4.5x12
N/A
21% Decrease
Powers et al. 2009
Texas
Plastic 4.5x12
No Change
No Change
Baxter 2014
Virginia
Plastic 4.5x12
Slight
Decrease
~25% Increase
R. Lipcius, VIMS, pers.
comm.
Virginia
Plastic 4.5x12
No Change
53% Decrease
Upperman et al. 2014
Virginia
Plastic 4.5x12
N/A
17% Decrease
Morris et al. 2011
Virginia
Plastic 4.5x12
N/A
47% Decrease
Morris et al. 2011
Virginia
Plastic 4.5x12
No Change
No Change
Rook et al. 2010
9
Table 4. Effect of 5 cm high BRD on crab catch
State
BRD
Type
Dimensions
(cm)
Change in
Crab Size
Change in
Crab Number
Reference
Alabama
Wire
5x15
N/A
31% Decrease
Coleman et al. 2011
Delaware
Wire
5x10
No Change
No Change
Cole and Helser 2001
Delaware
Wire
5x12
No Change
No Change
Cole and Helser 2001
Georgia
Plastic
5x15
No Change
~14% Decrease Belcher et al. 2007
Louisiana
Wire
5x10
N/A
38% Increase
Guillory and Prejean
1998
Maryland
Wire
5x10
No Change
No Change
Roosenburg and Green
2000
Mississippi Wire
5x15
No Change
No Change
Graham et al. 2011
Mississippi Wire
5x10
No Change
No Change
Cuevas et al. 2000
New Jersey Wire
5x10
No Change
No Change
Mazzarella 1994
New Jersey
Wire
5x10
No Change
10% Increase
Wood 1997
New Jersey Wire
5x10
No Change
49% Increase
Wood 1997
North
Carolina
Wire
4x15; 5x15
No Change
No Change
Chavez 2014
North
Carolina
Wire
5x16
N/A
No Change
Hart and Crowder
2011
North
Carolina
Wire
5x15
No Change
12% Decrease
Chavez and Williard
2017
South
Carolina
Plastic
5x15
N/A
N/A
Powers et al. 2009
Virginia
Plastic
5x15
No Change
No Change
Upperman et al. 2014
Virginia
Plastic
5x15
Slight
Decrease
No Change
Corso et al. 2017
Virginia
Plastic
5x15
Slight
Increase
No Change
Grubbs et al. 2018