MEPS 308:183-195 (2006)  -  doi:10.3354/meps308183

Intertidal migration and habitat use by subadult Dungeness crab Cancer magister in a NE Pacific estuary

Kirstin K. Holsman*, P. Sean McDonald, David A. Armstrong

School of Aquatic and Fishery Sciences, University of Washington, Box 355020, Seattle, Washington 98195, USA

ABSTRACT: Tidal migrations are inherent in the life histories of numerous demersal predators, and both the indirect and direct effects of these forays are important to the structure and function of littoral communities. In coastal estuaries of the Northeastern Pacific, Dungeness crabs Cancer magister are abundant and compose a significant portion of estuarine biomass. The nursery role of complex littoral habitats for young-of-the-year (0+) C. magister is well documented, yet the ecology of subsequent age classes within coastal estuarine systems, and within littoral areas in particular, remains unclear. The goal of our study was to elucidate habitat use and migratory patterns of subadult C. magister (40 to 130 mm carapace width; 1+ and >1+ yr classes) in littoral eelgrass Zostera marina, oyster Crassostrea gigas, and unstructured littoral habitats (ULH). We employed 3 sampling techniques (trapping, acoustic telemetry, and underwater video) designed to examine various aspects of migratory behavior within Willapa Bay, Washington, a representative coastal estuary. Baited trap surveys revealed that relative catches of subadult C. magister are 30 to 50% higher on ULH than eelgrass or oyster beds, and are negatively correlated with catches of another large cancrid crab, C. productus. Ultrasonic telemetry observations suggest that subadult C. magister making nighttime foraging incursions prefer ULH to other littoral habitats, and underwater video observations show that migrations are influenced by tidal rhythms since movements are correlated with the direction and velocity of current flow in adjacent channels. Our results dramatically alter the perception of C. magister as a predominantly sublittoral predator, and underscore the significance of littoral habitats as important foraging areas.

KEY WORDS: Cancer magister · Dungeness crab · Habitat · Preference · Intertidal · Foraging · Estuaries · Sublittoral

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