Behavioural interactions of diamondback terrapins with crab pots demonstrate that bycatch reduction devices reduce entrapment

Diamondback terrapins (Malaclemys terrapin) have experienced declines throughout their range, and accidental mortality in crab pots is a significant conservation concern. To minimize the risk of terrapins entering crab pots, researchers have suggested the use of bycatch reduction devices (BRDs) to reduce the size of crab pot openings and thereby exclude terrapins from entering crab pots. Despite these recommendations, few studies have observed terrapin interactions with BRDs and effectively evaluated the efficacy of these devices at preventing the entry of terrapins into pots. The objective of this study was to determine the effect of BRD presence and orientation on terrapin behaviour around crab pots and overall terrapin capture rates. In a controlled laboratory setting, terrapins investigated crab pots more frequently when crab pots were baited with fish versus chicken. Terrapins were captured more frequently when BRDs were not installed. The presence of the BRDs also increased the length of time necessary for a terrapin to enter a crab pot and decreased the proportion of entries relative to the number of investigations. Vertically-oriented BRDs were more effective than horizontally-oriented BRDs at reducing terrapin captures. To prevent the continued decline of terrapin populations due to crab fisheries, it is recommended that crabbers avoid the use of fish as bait in crab pots to reduce the attractiveness of pots to terrapins and fit all crab pots with vertically-oriented BRDs to reduce terrapin entrapment. Copyright © 2015 John Wiley & Sons, Ltd.