Evaluation of a small beach nourishment project to enhance habitat suitability for horseshoe crabs

Density of spawning females at Bowers Beach was 1.04 m− 2 in 2001 and 1.20 m− 2 in 2002. These rates are lower than at Ted Harvey Beach but reveal an increase in spawning while Ted Harvey Beach underwent a considerable decrease (2.63 m− 2 to 1.35 m− 2). Sediments low on the foreshore remained nearly saturated throughout the tidal cycle at both beaches. The average hydraulic conductivity on the upper foreshore at the non-treatment section at Bowers Beach (0.19 cm s− 1) was less than at Ted Harvey Beach (0.27 cm s− 1), and the finer, better sorted sediments at depth at Bowers Beach resulted in a higher porosity, creating greater moisture retention potential. Egg development was greatest at mid foreshore at all sites. Eggs at the lower foreshore elevation remained viable, but did not develop to the embryo stage. Between-beach differences were limited to high elevations where higher mortality occurred at Ted Harvey Beach due to desiccation. Adding small amounts of gravel to a sand beach may change the appearance of the surface but may not appreciably increase mean grain size and sorting at depth or the hydraulic conductivity over the spawning season. The pebble fraction may be important for site selection, but finer sizes may be more important for egg survival because of moisture retention.