Conservation status of the Tomales Bay Isopod Caecidotea tomalensis (Malacostraca: Isopoda)

Almost 50 years have lapsed since the last publication on the distribution and ecology of the Tomales Bay Isopod, Caecidotea tomalensis, a rare crustacean endemic to California's north coastal mountain region. The loss of the type specimen, taxonomic errors, and the presence of morphologically similar congeners have made it difficult to accurately assess its distribution and abundance. We revisited most of the historic locations of C. tomalensis, and present the results of these and other aquatic bioinventories and the examination of museum accession records. We detected at least 40 new populations and we expanded the species' range into Del Norte, Monterey, and Sonoma Counties. We also document the disappearance of several known populations, which is attributed to habitat degradation. We also made recommendations on the conservation ranking of the taxon and future research directions.