Disease issues relevant to the culture of shellfish in Atlantic and Pacific Canada

A project initiated in October, 2000 at the Atlantic Veterinary College and Pacific Biological Station (PBS) assessed the health/disease issues relevant to the culture of indigenous shellfish species. This project included a thorough geographic survey of infections affecting the Stimpson's bar clam (Mactromeris polynyma), European oyster (Ostrea edulis), green sea urchin (Strongylocentrotus droebachiensis), orange-footed sea cucumber (Cucumaria frondosa), and northern shrimp (Pandalus borealis) on the east coast, and the green and red sea urchin (S. droebachiensis, S. franciscanus), California sea cucumber (Parastichopus californicus), cockle (Clinocardium nuttallii), varnish clam (Nutallia obscurata) and pinto abalone (Haliotis kamtschatkana) on the west coast. All species are currently under culture development, or of culture interest, on their respective coasts. Gross observations found the presence of the boring sponge (Cliona vastifica) in the shells of O. edulis and Cliona sp., and Polydora sp. in the shells of abalone. Histological examination revealed organisms such as Trichodina sp., unidentified intestinal ciliates, Rickettsia-like organisms, unidentified copepods, Nematopsis-like gregarine spores, and digenean metacercarian cysts in or near tissues in the bivalves, echinoderms and crustaceans. It is essential to establish baseline information on what is 'normal' for species going into culture production to: (i) accurately assess disease risks, and (ii) differentiate true pathogens from opportunists taking advantage of sub-optimal culture conditions. This proactive research approach sets a precedent for the development of shellfish culture species, since health research rarely occurs before a disease crisis occurs.