HABITAT SELECTION BY YOUNG-OF-THE-YEAR DUNGENESS CRAB CANCER-MAGISTER AND PREDATION RISK IN INTERTIDAL HABITATS

Habitat selection by megalopae, and habitat preference and relative mortality of young-of-the-year (YOY) Dungeness crab Cancer magister Dana were evaluated in 4 habitat types: bivalve shell middens (Crassostrea gigas), eelgrass Zostera marina, mud with scattered shell and bare mud. Under laboratory conditions shell was the most preferred habitat by megalopae and YOY; eelgrass ranked second. Field tethering experiments showed that shell habitat provided the best protection from predation, and that the proportion of crab eaten was highest on bare mud. Field tethering experiments using small hooks attached to tether lines and glued to the crab showed that the sculpin Leptocottus armatus was the most important fish preying on YOY crab in this area. Cannibalism by larger instars of YOY, 1+ and 2+ Dungeness crab also may account for part of the YOY mortality. Most evidence suggests that intertidal shell habitat enhances Dungeness crab survival during the first several months of benthic life. It has led to the use of artificial shell habitat as a technique to increase juvenile crab abundance and compensate crab losses due to dredging.