Workshop to show: Shellfish diseases in
Bay warrant watchfulness, not panic

NARRAGANSETT -- August 17, 2000 -- Shellfish diseases that have damaged crops of oysters and clams in neighboring states have made their way into Narragansett Bay. But the situation calls for caution, not panic, because there are only a couple of locations where concentrations of infected shellfish are high.

This is the word from fish pathologist Marta Gomez-Chiarri, a University of Rhode Island fisheries, animal and veterinary science assistant professor. Gomez-Chiarri will report findings from a survey of locally identified shellfish diseases in a workshop Thursday, August 24. The presentation begins at 6:30 p.m. at the Coastal Institute, URI Bay Campus, Narragansett.

While Gomez-Chiarri focuses on diseases found in Rhode Island waters, Roxanna Smolowitz will contribute reports about Massachusetts shellfish diseases. Smolowitz is a veterinarian from the Marine Biological Laboratories in Woods Hole, Mass., who has researched QPX (quahog parasite unknown), among other diseases.

The scientists hope to alert shellfish harvesters and aquaculturists to infestations of parasitic diseases and to identify some of the conditions that signal disease presence. They will open their presentations to audience discussion of aquaculture, implications for fisheries, and management and regulatory issues.

Gomez-Chiarri's comments will update findings from the ongoing Shellfish Disease Survey Program, designed to map the incidence and intensity of various shellfish diseases in local waters. With research funded by the Rhode Island Department of Environmental Management's Division of Fish and Wildlife and outreach support from Rhode Island Sea Grant, her work will guide decisions by managers as well as harvesters and aquaculturists about where to harvest, when to harvest, where to gather seed, and where to transplant cultured shellfish.

Now in its third year, the survey targets two diseases-Dermo and MSX (Multinucleated Sphere X)-both caused by single-celled protozoan parasites and both affecting oysters. Dermo, Perkinsus marinus, kills by breaking (lysing) oyster tissue when it proliferates to high numbers. The Dermo parasite "loves warm temperatures," says Gomez-Chiarri, "so it proliferates in summer to the point that the oysters can't keep up with it." MSX infection kills fairly quickly by spreading throughout the oyster's tissue.

While not harmful to humans, according to Gomez-Chiarri, these parasites can wreak havoc with oyster crops. MSX can be transmitted from oyster to oyster, and Dermo can take as long as three years after infection to kill its host, gaining ample opportunity to spread to healthy mollusks. In both cases, a major path to infection is transplantation of healthy oysters into infected beds or infected animals into clean beds.

Gomez-Chiarri notes that, even if there's not much fishermen can do about disease, "if they know what places in the bay have problems, they can harvest or they can get seed elsewhere."

For information about the survey, sites of infestation, other disease organisms identified and their impact on shellfish, contact David Beutel, URI fisheries, animal and veterinary science, (401) 874-7152.

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Contact: Tony Corey, (401) 874-6844