The Effects of Bycatch Reduction Devices on Crab Catch Rate

Overview

The native population of diamondback terrapins (Malaclemys terrapin) has been on a steady decline throughout the past century on the East and Gulf Coasts. Currently, their numbers are being decimated by the blue crab (Callinectes sapidus) fishery. The crab pots employed in this industry catch not only large quantities of blue crabs, but also the diamondback terrapins, which then drown in the pots. Recently, scientists have come up with a solution that will exclude the diamondback terrapins from entering the crab pots while still allowing the blue crabs to enter. These devices are called bycatch reduction devices (BRDs) and the purpose of this study was to test the effects that they have on the number and size of blue crabs caught in their pots. Ten crab pots were deployed randomly, five containing BRDs and five without BRDs, in two parallel lines. At the halfway mark in the study, the two lines of pots were switched. Crab catch rate for each crab pot and carapace lengths of each crab were measured every two to three days for a total of two weeks. This study found that while the BRDs do not affect the size of crabs caught, they do negatively affect the number of crabs that outfitted pots are able to catch, perhaps due in part to increased algae growth on the devices themselves.