Estimation of wave energy using fetch and wind data at horseshoe crab spawning beaches along the Connecticut coast

The Atlantic horseshoe crab, Limulus polyphemus, requires estuarine beaches for egg incubation during May and June.  As part of ongoing research, we are combining field surveys and spatial data to classify beach habitats along the northern shore of Long Island Sound in order to predict their probability of use by spawning horseshoe crabs. Relative wave energy at the shoreline is a potentially important driver of horseshoe crab population dynamics as breeding adults are known to select lower energy beaches and will avoid laying eggs during periods of heavy wave action. Wave energy was estimated using wind speed and predominant direction data along with fetch distances calculated in ArcGIS. Fetch lines radiating from shoreline points (spaced every 50 meters) to non-open water features (breakwaters, islands, etc.) in several directions were summed, with weight given to those distances lying in dominant wind directions. These values, along with wind magnitude data, were used to calculate estimated wave heights, which are proportional to wave energy. This information will ultimately become part of a resource selection model used to predict the suitability of beaches for horseshoe crab spawning.