Meeting Abstract

82.5  Friday, Jan. 6  Using a Spatially-Explicit Predator-Prey Model to Investigate Bycatch Risk of Terrapins in Crab Pots HARDEN, L.A.*; WILLIARD, A.S.; UNC Wilmington

Trends in diamondback terrapin Malaclemys terrapin abundance and demography suggest that crab pot bycatch mortalities may be contributing to population declines of this estuarine turtle. Designing effective regulations to minimize terrapin-crab pot interactions requires information on the spatial ecology and seasonal behavior of terrapins. Thus, our goals are to 1) identify spatial and temporal aspects of terrapin-crab pot overlap and 2) assess the likelihood of encounters (bycatch risk) based on densities and distribution of crab pots and terrapins as well as terrapin behavior in North Carolina. We radiotracked 29 terrapins and documented their locations and behavior, as well as the locations of nearby crab pots, in sounds where crabbers have observed terrapin bycatch. Terrapin and environmental temperatures were also recorded using micro-dataloggers to provide a more detailed profile of activity and habitat use. Spatial and temporal interactions between terrapins and crab pots were determined using GIS to calculate their seasonal distributions and densities and then using a spatially-explicit predator-prey model to assess their spatial overlap. This model has been used in previous studies to predict areas of high bycatch by comparing the density and distribution of fishing effort (predator) to that of the marine bycatch species (prey) and describes the degree to which the spatial correlation of predator and prey deviates from the random expectation under uniform spatial distributions. Results indicate that spatial overlap is greater in warm months when terrapins are swimming in the same shallow, near shore habitat as blue crabs. Moreover, when seasonal and semi-aquatic behavior of terrapins is incorporated into the spatial model, bycatch risk is reduced.