Spatial Variation in Nursery Habitat Use by Juvenile Blue Crabs in a Shallow, Wind-Driven Estuary

Nursery habitats promote the survival of juveniles to the adult population and are often targeted by conservation policies and restoration practices. Managers must choose where to focus limited resources, which is complicated when juveniles utilize multiple habitats. This is particularly applicable to the blue crab ( Callinectes sapidus ) population in North Carolina, USA, which uses three main habitats, low salinity ephemeral Ruppia maritima seagrass beds, high salinity mixed-species seagrass beds, and shallow marsh detrital habitat (SDH). Spatial variation in early juvenile blue crab density and size-class of blue crab instars (2.2–20 mm) was quantified within the Albemarle-Pamlico estuarine system (APES) together with potential explanatory variables such as habitat structural complexity and proximity to inlets, potentially driving spatial variation in crab density and size. Despite being 25–40 km from oceanic sources of megalopae, juvenile crab density was nearly four times greater in ephemeral R. maritima habitat on the western shore of the APES than adjacent SDH or mixed-species seagrass beds located near inlet sources. Increased crab density in western habitats may be a result of cross-sound transport being hurricane-driven as opposed to secondary density-dependent distribution resulting in increased recruitment to western habitats. Local-scale factors also affected crab distribution patterns. For example, mean crab density in mixed-species seagrass beds along the eastern shore decreased by approximately 87% over a distance of 26.6 km from inlet sources of megalopae. Mean crab density in western R. maritima beds increased tenfold between locations with the lowest shoot density (~ 14,000 shoots m −2 ) to that with the highest (~ 54,000 shoots m −2 ). This study highlights how regional postlarval dispersal patterns and local-scale factors affect nursery habitat use by blue crabs when multiple habitats are present in a seascape.