Impact of a bycatch reduction device on diamondback terrapin and blue crabcapture in crab pots

Bycatch in fisheries is receiving attention because of its impact on ecolog ical diversity and resource sustainability. Male and juvenile female diamon dback terrapins, Malaclemys terrapin? frequently drown as bycatch in crab p ots, removing individuals with high reproductive value from the population and possibly skewing sex ratios. We tested a wire bycatch reduction device (BRD) to determine its ability to reduce terrapin entrapment and to examine any effects the BRD has on the size and number of blue crabs, Callinectes sapidus, caught in crab pots. We tested three sizes of BRDs, a 4 X 10 cm BR D in 1996, and 4.5 x 12 cm and 5 X 10 cm BRDs in 1997. We equipped both sta ndard crab pots and modified (tall) crab pots with BRDs, the latter were us ed to prevent terrapin mortality in areas of high terrapin density. Traps w ere checked and baited daily. In 1996, we caught no terrapins in 14 crab po ts equipped with the 4 X 10 cm BRDs and 21 terrapins in II crab pots withou t BRDs. In 1997, the 4.5 X 12 cm BRD reduced terrapin bycatch by 82%, where as the 5 x 10 cm BRD reduced terrapin bycatch by 47%. The 4 X 10 cm BRDs, h owever, reduced the size and number of large "Number One" and mature female crabs. Catch rate for standard crab pots with 4 X 10 cm BRDs was 2 crabs.p ot(-1).day(-1) lower than standard crab pots fished without BRDs in 1996. N either the 5 X 10 cm BRD nor the 4.5 x 12 cm BRD affected crab size or the number of crabs caught in crab pots. Standard crab pots with a 4.5 X 12 cm BRDs had the highest catch per unit effort (2.69 crabs.pot(-1).day(-1)), fo llowed by standard crab pots without BRDs (2.55 crabs.pot(-1).day(-1)) and standard crab pots with 5 x 10 cm BRDs (7.39 crabs.pot(-1).day(-1)). The la rgest crab caught in 1997 was in st crab pot with a 4.5 x 12 cm BRD. We str ess the importance of using the 4.5 X 12 cm BRD on crab pots fished commerc ially and recreationally to reduce terrapin mortality and the need to integ rate the use of BRDs on crab pots with ether conservation practices such as protection of critical terrapin habitat, particularly nesting beaches.