Evaluating risks associated with transport of the ghost shrimp Neotrypaea californiensis as live bait

The ghost shrimp Neotrypaea californiensis is imported into southern California from Oregon and Washington for use as live bait in recreational marine fisheries. We studied the population genetic structure of N. californiensis across much its range to assess the possibility that the transport of ghost shrimp across phylogeographic boundaries poses a risk of homogenizing existing genetic variation in the species. Analyses of two mitochondrial DNA markers showed little phylogeographic structure across the sampled range, suggesting that this risk is low. Unexpectedly, mitochondrial DNA analyses revealed that a second putative species of ghost shrimp frequently coexisted with N. californiensis in southern California intertidal habitats; almost all previous studies of soft-sediment communities in the region report the presence of N. californiensis only. We also assessed the possibility that the import of ghost shrimp might pose a risk of introduction of a parasitic castrator, the bopyrid isopod Ione cornuta, into southern California waters, where it does not appear to be native. Prevalence of living I. cornuta in samples purchased from bait shops was high (5.8%), suggesting that this is a real risk that merits further study.