Masters Thesis

The Susceptibility of California's Wild and Cultured Abalone to the Ectoparasitic Snail (Evalea tenuisculpita)

Purpose of the Study: Ectoparasites in the family pyramidellidae have been known to have negative impacts on mollusk fisheries by causing shell malformation, reduced growth, transmission of disease, and mortality. Although common pests in fisheries worldwide, little is known about these pyramidellids in western fisheries. A study done in 2011, showed 40% of wild red abalone from Sea Ranch, California had this parasite and anecdotal evidence suggests these parasites are found in heavy infestations in aquaculture. Currently, nothing is known about the prevalence or infection intensity of Evalea tenuisculpita. The high infection rates and parasite loads on abalone, combined with abalone's conservation status and market value begs additional investigations into the basic ecology of this host-parasite relationship. As abalone aquaculture continues to expand, parasite infestations may impact sustainability justifying contamination prevention from an economical and ecological perspective. Knowing the baseline distribution and infection intensity may benifit sustainability of aquaculture, the recovery of endangered species, and the health wild populations. The information we discover may not only be applicable to the abalone, but to scallop, clam, and mussel fisheries also. The purpose of this study is to understand the prevalence, ecology, and size frequency of the pyramidellid parasite, Evalea tenuisculpita, which infects abalone in California. Procedure: We used SCUBA surveys, aquaculture surveys, and fisherman interviews to access the prevalence, infection intensity, and size structure of E. tenuiscupita in the wild and aquaculture. Findings: The parasitic snail Evalea tenuisculpita was commonly found in aquaculture and in the wild throughout California. While there was a slightly higher prevalence of this parasite in the wild, larger parasites were found under culture conditions. Abalone captured from the wild and raised in aquaculture on non-treated water had the highest parasite loads of all abalone sampled. Conclusions: While we don't believe E. tenuisculpita is invasive in the wild, aquaculture conditions may facilitate outbreak of these parasites. We hypothesize the introduction of infected wild abalone into aquaria may facilitate explosion and parasite growth and recommend quarantining abalone and removing parasites before abalone are introduced to aquacultured populations. More investigations are needed on this parasite to address potential removal methods for this parasite.

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