Temporal variation and habitat use of nearshore crab populations in Kachemak Bay, Alaska

Abstract

Larval, juvenile, and adult crab distribution was surveyed in three different habitats in Kachemak Bay, Alaska from June 2005 to September 2006 to determine temporal and spatial variability. Crab distribution varied temporally and spatially in all life stages. Nine sites of varying habitat complexity were surveyed monthly using scuba, light traps, and shrimp pots to measure habitat variables, quantify larval, juvenile, and adult crabs, and survey potential crab predators. No single bay-wide variable determined the appearance of all crab larvae. Spatial differences in larval abundance probably resulted from large scale physical transport mechanisms. Overall juvenile and adult crab abundance increased with habitat complexity; however species richness was not positively correlated with complexity. This study suggested that the canopy structure provided by Nereocystis luetkeana had minimal effects on spatial crab distribution in all life stages. Canopy structure may not influence the spatial distribution of larval crabs and is thought to have little importance for juvenile and adult crabs. Understory kelp density may more directly affect juvenile and adult crabs by providing more microhabitats for refuge. Habitat use and the importance of structural complexity vary by life history stage and species depending on survival strategy.