Document Type



Virginia Institute of Marine Science

Publication Date



Proceedings of the National Shellfisheries Association





First Page



In 1950 Mackin, Owen, and Collier described a fungus parasite, Dermocystidium marinim, found in oysters of Louisiana coastal waters. Since that, time numerous studies have been conducted on the nature of the fungus and its effects upon the host. It has been definitely established that the pathogen is the main contributor to the causes of mortality of oysters in some areas. Ray and Chandler (1955) have adequately reviewed the literature on the subject.

Among the various observations that have been made on the fungus disease there is very positive evidence that the incidence and intensity of the infection are primarily controlled by the temperature of the water. Mackin (1953) found that mortality rates and intensity of the infection were greatly depressed during the winter months in Barataria Bay, Louisiana. Hewatt and Andrews (1953) reported a high mortality period extending from June through October in the lower York River, Virginia., Ray and Chandler (1955) stated that temperatures exceeding 20°c. favor the development of Dermocystidium marinum in waters of the Gulf of Mexico.

During the summer of 1954 we conducted a series of experiments in an effort to determine the effects of relatively low and high temperatures on the development of the fungus disease. Oysters were collected from two different sources. One group of oysters, estimated to be three years of age, was collected from Wreck Shoal of the James River, where no evidence of the fungus has been found. This group 'Will be referred to as the "Nonendemic Oysters"& The other group of oysters came from the Rappahannock River, where fungus infections have been found. This group will be designated "Endemic Oysters" ..