Abundance of Crab Species and Parasites in the Potomac River

Abstract

Rhithropanopeus harrisii can tolerate a wide range of salinities from 0.5 to 27.5 ppt. While Eurypanopeus depressus usually is found within the 4.5-20.4 ppt range, and Panopeus herbstii from 13.95-19.04 ppt (Williams 1984). Both R. harrisii and E. depressus are susceptible to infection from the parasite, Loxothylacus panopaei (Alvarez et al. 1995, Kruse et al. 2011, O’Shaughnessey et al. 2014). L. panopaei takes over the crab’s reproductive system, castrating them and feminizing males. L. panopaei cannot tolerate salinities less than 10ppt (Boyle et al. 2010) allowing for there to be a potential refuge for mud crabs in these lower salinities. In this study, we collected crab samples from five different sites along the Potomac River. The samples were sorted by species, sex, size, and parasite infection. The purpose of this study was to identify the effect of salinity on crab species abundance and parasite prevalence. It was hypothesized that the parasite would be found in higher salinity sites, and there would be a greater overall abundance and diversity of crabs at higher salinity sites. It was found that the diversity of crab species increased as salinity increased. However, the most amount of parasitized crabs was found in the mid salinity range. This may be because there is a higher population of crabs overall in the mid salinity sites, so there is more opportunity for infection in those sites.