Document Type



Virginia Institute of Marine Science

Publication Date



Marine Resource Advisory No. 74; VSG-02-18


T he results of recent investigations by VIMS and collaborating scientists in Massachusetts and New Jersey indicate that clam strains produced from brood stocks of South Carolina and Florida origin are more susceptible to QPX (Quahog Parasite Unknown) disease than clam strains originating from Virginia, New Jersey, and Massachusetts brood stocks. During a 3-year study clam strains produced at VIMS from brood stocks originating from Massachusetts, New Jersey, Virginia, South Carolina, and Florida were grown at sites in Massachusetts, New Jersey and Virginia and evaluated for survival, growth, condition and QPX disease susceptibility. The clams originating from South Carolina and Florida brood stocks had significantly higher prevalence of QPX and higher mortality than clams originating from Virginia, New Jersey and Massachusetts brood stocks. At the termination of the experiment cumulative mortality was 79% in FL and 52% in SC, as compared to 36% in VA, 33% in MA, and 20% in NJ clams. Differences between stocks were highly significant with mortality in FL and SC being significantly higher than the northern stocks. QPX prevalence in the FL and SC stocks ranged from 19-21% and 27-29% respectively in the second and third year of the study, while QPX prevalence in the VA, NJ, and MA stocks was 10% or less. Mortality was significantly correlated with QPX prevalence during the second and third years of the investigation



Quahog Parasite Unknown, Clam, Diseases, Aquaculture



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