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