Selection of Spawning Habitats by Horseshoe Crabs (Limulus polyphemus) along the Complex Connecticut Coast

The Atlantic horseshoe crab (Limulus polyphemus) is a multiple-use resource that has recently come under environmental conflict. This research focused on the Long Island Sound population of horseshoe crabs and aimed to characterize the coastal habitats of Connecticut by various traits using remote sensing and geographic information system technologies. Data layers representing the coastal area were created within which slope, wave exposure, substrate type, and distance from offshore aggregations of crabs were summarized for the western, central, and eastern regions of Connecticut. Spawning abundances derived from field surveys of a subsample of sites conducted in May-June of 2009 and 2010 were used with the remotely sensed habitat characteristics to develop a resource selection function from a candidate model set based on polytomous logistic regression. An information-theoretic approach was followed to select a best approximating model that included slope, wave exposure, and distance (Akaike weight = 0.967). The parameter estimates predicted a higher probability of habitat use with increasing slope, decreasing wave exposure, and decreasing distance from offshore hotspots. High use areas were predicted to cover 34.60% of the total coastal area with half of those areas occurring in the western region of Connecticut. Quasi-validation of the model showed 61.90% agreement between observed and predicted habitat use, with no high use sites misclassified as low use and vice versa. This research described the potential spawning habitats of horseshoe crabs at a landscape scale and can be used by habitat managers as a starting point for selection of sites for spawning surveys and regulations