Diamondback Terrapin (Malaclemys terrapin) Mortality in Crab Pots

Abstract

The entrapment of diamondback terrapins ( Malaclemys terrapin) in crab pots frequently results in drowning and death of the trapped turtles. We determined the rate of capture, size, sex, and age of terrapins captured, and the potential impact crab pot mortality has on local terrapin populations. We estimated terrapin capture rates of 0.17 terrapins/pot/day in shallow water areas of Chesapeake Bay (Maryland, USA). The sex ratio of terrapins caught in crab pots was 3:2 male biased because female terrapins become too large to enter crab pots by the time they reach 8 years of age. Males, however, remain vulnerable to entrapment throughout their life. Our estimates of capture rates and local population size suggest that 15–78% of a local population may be captured in a single year. As a consequence, crab pots may be the major reason terrapins are extirpated in coastal, shallow water areas with heavy crab pot fisheries. Additionally, the selective removal of males may also contribute to female‐biased sex ratios observed in this diamondback terrapin population. We developed and tested a modified crab pot that increases terrapin survival and does not reduce the number of crabs caught. Our modified crab pot maintained permanent access to air and prevented the drowning of terrapins. Additionally, our modified crab pot caught more crabs than standard commercial crab pots, suggesting that the modified crab pot could be a viable alternative to standard traps that result in terrapin mortality.