Evaluating Methods for Estimating Delaware Bay Limulus polyphemus Abundance

Abstract

Monitoring is an essential component of wildlife management. In the United States, Atlantic horseshoe crabs (Limulus polyphemus) are harvested and relied upon by several user groups in mid-Atlantic states, and managers have used offshore trawl surveys to monitor the species. However, this monitoring method is expensive and has an uncertain future in management efforts. Utilization and analysis of volunteer-collected, mark-recapture data may serve as a more feasible monitoring alternative. Our objectives were to evaluate the utility of a hierarchical, state-space modeling approach within a Bayesian framework for estimating the Delaware Bay spawning population using 2003 and 2004 volunteer-collected data. We compared our model’s analysis of those data to trawl survey data analyses of those years. We also evaluated the effects of increasing tagging and recapture effort on our model’s estimates. Our estimates were comparable to those of past trawl surveys, and our approach may be a viable monitoring alternative.