Bycatch reduction device conserves diamondback terrapin without affecting catch of blue crab

Abstract

Bycatch mortality of non-target species in fisheries is a major threat to the conservation and restoration of marine and estuarine species. Attempts to reduce bycatch by fitting fishing gear with excluder devices have typically been met with resistance due to reductions in catch of target species. We examined the possibility that conservation and fishery goals could be met simultaneously. In lower Chesapeake Bay, we tested a mechanism for reducing bycatch of diamondback terrapin Malaclemys terrapin in blue-crab traps without affecting crab catch. Over 23 sampling dates during summer 2008, we compared terrapin captures at 2 shallow-water sites typical of recreational crabbing, using 10 paired sets of an un-baited trap fitted with bycatch reduction devices (BRDs) and a trap without BRDs at each site on each date. In a separate experiment, traps were baited and fished 4 times during the summer, when we recorded number, size, and condition of captured crabs. Of 48 terrapin captures in crab traps, only 2 were from traps fitted with BRDs. Crab catch (number, size, and biomass) was equivalent between traps with and without BRDs. Because BRDs are effective in excluding all but the smallest terrapins from entering crab traps and had no effect on crab catch, BRDs are recommended for all recreational crab traps at this time and should be seriously considered for commercial traps throughout shallow estuarine waters. Combined with bycatch reduction policies in other North American estuaries, a comprehensive and effective strategy for the conservation of diamondback terrapin threatened by fisheries is emerging. 409: 171-179, 2010 mondback terrapin and the blue crab Callinectes sapidus fishery. The diamondback terrapin Malaclemys terrapin is the only turtle in North America to inhabit estuarine environments exclusively (Ernst et al. 1994). Terrapins, while generally considered Kselected species living in excess of 40 yr, become sexually mature between the ages of 6 and 13 yr, yet exhibit a reproductive strategy in which many eggs are produced but only a few survive to adulthood (Hildebrand 1932, Roosenburg & Green 2000. Terrapins are potentially keystone predators in estuarine ecosystems, feeding on prey such as crabs, mussels, salt marsh periwinkles, barnacles, and clams (Tucker et al. 1995, Silliman & Bertness 2002. The most abundant and common prey is the salt marsh periwinkle Littoraria irrorata, which comprises as much as 79% of the total food intake by mass in some areas (Coker 1920, Tucker et al. 1995. When unchecked by predators, L. irrorata can defoliate a marsh in as little as 8 mo (Silliman & Bertness 2002). Adult terrapins in turn are prey of bald eagles (Clark 1982) and may be eaten by toadfish and crabs (Cecala et al. 2008). KEY WORDS: Bycatch reduction device · Diamondback terrapin · Blue crab · Trap mortality Resale or republication not permitted without written consent of the publisher OPEN PEN ACCESS CCESSMar Ecol Prog SerTerrapins have a long history of overexploitation, having been hunted to co...

Mitigating unaccounted fishing mortality from gillnets and traps

“…) or remain until the trap is hauled (Rook et al . ). In some cases, changes to the material have allowed organisms to detect and avoid the gear altogether (Trippel et al .…”

Fishing methods for sustainable shrimp fisheries in the Canary Islands (North-West Africa)

“…A chi-square test (χ 2 test, p ≥ 0.05) was used to investigate possible differences among averages of CPUE per trap type. Bycatch and discard species collected were also quantified (CPUE) to explore possible effects of trap types in competition and predation of the target species as a contribution to the development of an ecological approach to the fishery (García-Rodríguez et al 2000, Rook et al 2010.…”

Size-Based Mortality of Adult Female Diamond-Backed Terrapins (Malaclemys terrapin) in Blue Crab Traps in a Gulf of Mexico Population

“…It is generally accepted that males and juvenile females are more vulnerable to crab-trap mortality than are adult females (Roosenburg et al 1997;Roosenburg and Green 2000;Gibbons et al 2001;Butler and Heinrich 2007;Dorcas et al 2007;Hart and McIvor 2008;Rook et al 2010;Wolak et al 2010;Coleman et al 2011;Hart and Crowder 2011;Baxter 2013). However, Roosenburg (2004) suggested that regional studies should determine which sex and life-history stages are susceptible to crab-trap mortality.…”

“…Numerous studies have shown that BRDs reduce terrapin bycatch while not significantly depressing blue crab catch (Mazzarella 1994;Roosenburg et al 1997;Cuevas et al 2000;Roosenburg and Green 2000;Butler and Heinrich 2007;Rook et al 2010;Hart and Crowder 2011;Morris et al 2011;Baxter 2013;Upperman et al 2014), perhaps even increasing it (Wood 1997;Guillory and Prejean 1998). Guillory and Prejean (1998) suggested that BRDs might provide rigidity to funnel openings, thus reducing crab egress.…”