ESR 5:279-289 (2008)  -  doi:10.3354/esr00105

Hierarchical modeling of bycatch rates of sea turtles in the western North Atlantic

Beth Gardner1,3,*, Patrick J. Sullivan1, Sheryan Epperly2, Stephen J. Morreale1

1Dept. of Natural Resources, Cornell University, Ithaca, New York 14853, USA
2NOAA, National Marine Fisheries Service, Miami, Florida 33149, USA
3Present address: US Geological Survey, Patuxent Wildlife Research Center, Laurel, Maryland 20708, USA

ABSTRACT: Previous studies indicate that the locations of the endangered loggerhead Caretta caretta and critically endangered leatherback Dermochelys coriacea sea turtles are influenced by water temperatures, and that incidental catch rates in the pelagic longline fishery vary by region. We present a Bayesian hierarchical model to examine the effects of environmental variables, including water temperature, on the number of sea turtles captured in the US pelagic longline fishery in the western North Atlantic. The modeling structure is highly flexible, utilizes a Bayesian model selection technique, and is fully implemented in the software program WinBUGS. The number of sea turtles captured is modeled as a zero-inflated Poisson distribution and the model incorporates fixed effects to examine region-specific differences in the parameter estimates. Results indicate that water temperature, region, bottom depth, and target species are all significant predictors of the number of loggerhead sea turtles captured. For leatherback sea turtles, the model with only target species had the most posterior model weight, though a re-parameterization of the model indicates that temperature influences the zero-inflation parameter. The relationship between the number of sea turtles captured and the variables of interest all varied by region. This suggests that management decisions aimed at reducing sea turtle bycatch may be more effective if they are spatially explicit.


KEY WORDS: Longline fisheries · Bycatch · Sea turtles · Hierarchical models


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Cite this article as: Gardner B, Sullivan PJ, Epperly S, Morreale SJ (2008) Hierarchical modeling of bycatch rates of sea turtles in the western North Atlantic. Endang Species Res 5:279-289

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