Reprint Series No. 18

ABUNDANCE, SETTLEMENT, GROWTH AND HABITAT USE BY JUVENILE DUNGENESS CRAB, CANCER MAGISTER, IN INLAND WATERS OF NORTHERN PUGET SOUND, WASHINGTON

Russell O. McMillan

August 1991

Bibliographic Citation
McMillan, Russell O. 1991. Abundance, settlement, growth and habitat use by juvenile dungeness crab, cancer magister, in inland waters of northern Puget Sound, Washington. Seattle, Washington. 53 pp. Padilla Bay National Estuarine Research Reserve Reprint Series No. 18.

Abstract
Abundance, growth and habitat use by early post-larval Dungeness crab, Cancer magister, were examined at 5 northern Puget Sound sites between June 1984 and September 1987. Sampling was conducted in intertidal habitats biweekly during settlement and approximately monthly or bimonthly thereafter. Northern Puget Sound Dungeness crab populations appear to be largely supported by recruitment from inland parental stocks with occasional recruitment originating from coastal or oceanic stocks. Settlement of Dungeness crab in inland waters typically peaked in August and interannual variation in yearclass strength at settlement was low relative to that reported for coastal crab populations. Spatial and interannual differences in settlement densities were mediated by high post-settlement mortality. Post-settlement growth rates corresponded to seasonal water temperatures and were greatest for the coastal cohort that settled in early summer. These crab grew rapidly to a size that allowed emigration from intertidal to subtidal areas by September. Emigration of the late summer cohort which settled in August occurred the following spring, about 10 months after settlement when crab appear to have acquired refuge from predation in size. Mean seasonal densities of 0+ age juvenile crab corresponded to habitat complexity. Densities were highest in mixed sand and gravel with an overstory of attached or drift macroalgae, intermediate in eelgrass (Zostera marina) and lowest on bare sand.