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Kathryn Loftus - Invasions Ecology Lab

Humboldt State University, CA

The white fingered mud crab, Rhithropanopeus harrisii, is a small crab that is common in oyster beds, and around woody debris.  I examined this crab's habitat use by sex and size.  I deployed crab collecting units (CCU) at two sites close to the Smithsonian Environmental Research Center on the Rhode River.  Three different types of CCUs were used to determine if crabs actively seek out one type of habitat.  Six CCUs were deployed at each site and retrieved once a week for six weeks from June 23rd until August 2nd, 2005. All the crabs were removed from the collectors and counted.  Crabs greater than 4mm were measured and sexed.  I found that male crabs and non-ovigerous females were more abundant in oyster collectors at both sites.  Small crabs (<4mm) were more abundant in oyster collectors at only one site, suggesting that physical characteristics of the site may also play a role in the desirability of the artificial habitats.  Ovigerous females were equally abundant in all three types of CCUs.