Striped bass cooperative study to determine the cause of ulcerative dermatitis syndrome
Report for December 10, 1997 conference to investigate the decline of the Striped Bass forage base.
The dramatic decline of the Chesapeake Bay’s two most abundant and important species of forage fish, the Bay Anchovy and the Atlantic Menhaden, are threatening the health of the Bay’s Striped Bass population. Possibly, the ecology of the entire Chesapeake Bay will be affected by the reduced numbers of these two important sources of food for the Bay’s finfish population.
According to information obtained from the Maryland Dept. of Natural Resources Estuarine Juvenile Finfish Survey, the 1994 to 1997 average relative abundance of the Bay Anchovy is at it’s lowest level ever recorded. Also, the average relative abundance of Atlantic Menhaden from 1992 to 1997 are comparable to the lowest levels recorded from the late 1950’s and early 1960’s. Maryland’s Chesapeake Bay pound net catch per unit effort of Atlantic Menhaden has dropped from 10,000,000 pounds in 1980 to an average of 2,000,000 pounds per year since 1992. The Atlantic Menhaden has also been declining along the Atlantic coast as well as in Maryland’s portion of the Chesapeake Bay. According to an April 1997 report by the National Marine Fisheries Service, “the estimate for 1996 of 1.1 billion age-1 Menhaden does fall below the trigger value of 2.0 billion age-1 Menhaden”, established by the Atlantic States Marine Fisheries Commission’s Atlantic Menhaden Fishery Management Plan. “The recent 3 year running average of 1.8 billion age-1 Menhaden is also below the trigger value”, established by the Atlantic Menhaden Fishery Management Plan.
In recent years, the general health and condition of larger Striped Bass has declined. During 1997, large numbers of these fish exhibited signs of malnutrition and starvation, and approximately 11.5% of these fish now have visible bacterial infections, usually identified by the appearance of red sores of varying sizes, from pinpoint to larger ulcerations that result in an unsightly deterioration of the skin. Dr. Eric May, of the MD-DNR, has classified this condition as “Ulcerative Dermatitis Syndrome.”
Based on the examination of stomach contents of 18-inch-plus Striped Bass caught in the lower Choptank River and middle Chesapeake Bay region from 1990-1997, the presence of Blue Crab, White Perch, Spot and Sand Shrimp currently appear to have replaced the Bay Anchovy and the Atlantic Menhaden as the food most often found in their stomachs during the Summer and Fall seasons. A total of 13 Striped Bass, ranging in size from 18″ to 22″, caught in the mid-Bay during the last week of November were examined and nine of these fish had been unable to accumulate body fat which indicates their inability to locate the amounts of the necessary type of food they normally require. The remaining four Striped Bass had a small amount of fat in their body cavities. The stomach contents contained a combination of Clam chum and Sand Shrimp. There was no evidence of Atlantic Menhaden or Bay Anchovies in any of their stomachs except for one fish that had 5 ounces of Menhaden chum in it’s stomach. Seventy-two sand shrimp were found in their stomachs, weighing a total of 2.6 ounces, averaging less than 0.2 ounces of Sand Shrimp per fish. Eleven ounces of Clam chum was found in their stomachs, for an average of 0.8 ounces per fish. A total of 18.6 ounces of food was found in the stomachs of the 13 Striped Bass examined: 14% was natural food, 86% consisted of chum. The total amount of natural food found in 12 of the Striped Bass only equaled half the amount found in one Striped Bass feeding on Menhaden chum.
In recent years, chumming has become one of the most popular and effective methods used to catch Striped Bass in the Chesapeake Bay. Historically, trolling was more productive when Striped Bass were attracted to large schools of Anchovies and Menhaden. The charter boat fleet and the commercial hook-and-line fishermen now use cut or ground-up chum to attract Striped Bass during most of the fishing season. Ironically, many recreational fishermen don’t believe the MD-DNR’s figures on the relative abundance of Striped Bass in the Chesapeake Bay, because they are having difficulty catching their limit of two fish per day over 18″. Recreational fishermen that have continued to use artificial baits haven’t been as successful in recent years, partly because they depend on locating their fish by sighting Gulls working over schools of breaking fish. Catching larger Striped Bass on the surface has become increasingly difficult since the large schools of forage fish have disappeared from the Bay.