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Aug. 5, 2010
The Maryland Department of the Environment and the Department of Natural Resources continue to investigate a large fish kill that occurred two weeks ago in Deep Creek Lake, Garrett County. In consultation with the Garrett County Health Department, MDE and DNR are providing additional information regarding necessary public health precautions.
Visitors and residents are advised to avoid touching, eating, or otherwise coming into proximity to any dead fish or fish with outward signs of stress or disease. Extra precautions should be taken for those with open wounds. Dogs, and other pets should be restricted from coming in contact with dead or dying fish. The best method to dispose of the fish is by burying them.
Analysis of samples collected by the Garrett County Health Department at 21 different sampling points around the lake the week of July 18 indicated low levels of E.coli bacteria at all locations. Swimming in Deep Creek Lake does not pose any additional public health risk at this time, although dead fish floating in the water should be avoided if possible.
The bacteria thought to be responsible for the fish kill has been identified as Aeromonas species, which has been known to cause other fish kills in Maryland. State health officials note that while this organism can cause infections through skin wounds, it has not been commonly associated with outbreaks in swimming areas. Therefore, no specific advisories are being issued regarding recreational water contact at Deep Creek Lake, except those related to direct contact with fish as described above.
The investigation is still ongoing, according to the MDE. Preliminary results indicate that unprecedented high temperatures in July in the surface waters of the lake are causing fish to be stressed and set the stage for a parasite protozoan infestation. This leads to a lethal secondary bacterial infection, primarily affecting fish in the lower upstream section of the lake.
The bacteria causing this secondary infection, Aeromonas hydrophila, is commonly present in the intestinal tract of healthy fish, said a DNR spokesperson. The affected fish were initially cold-water species such as yellow perch, walleye, smallmouth bass, and northern pike that are adapted to temperatures less than 73.4 degrees Fahrenheit/23 degrees Celsius. Warm-water species such as largemouth bass, catfish, and bluegill sunfish are now also being affected.
While a fish kill of this type is rarely seen in Deep Creek Lake because of its normally low water temperatures, it is not uncommon in other areas of the state, according to the DNR.
