Frequently asked questions about the dead fish in Deep Creek Lake
August 3, 2010
Is it safe to swim in the water at Deep Creek Lake? Yes. The fish are not dying because of a water contact problem but because two pathogens have taken advantage of the stressed condition of the fish and caused them to become weakened and die. Recreational users of the lake should always use caution when swimming in natural waters by avoiding contact with the water if they have open or new wounds or have a compromised immune system, as all such waters contain a wide variety of naturally occurring bacteria.
Why are the fish stressed? The temperature of the water in Deep Creek Lake during July has been the highest ever recorded over several decades of temperature monitoring. The fish are finding very warm water in the upper surface waters (78 – 80 degrees F). The lower layer of the lake water has naturally occurring low dissolved oxygen, limiting good available habitat for the fish. These two factors cause stress for fish.
What caused the fish to die? The Maryland Department of Environment fish biologist who specializes in determining the cause of fish kills has determined from samples taken from affected fish in Deep Creek Lake that two pathogens are at work here: one is a protozoan (gill parasite) and the other is a bacteria Aeromonas hydrophila.
Why is Aeromonas hydrophila here in the lake this year? This bacteria is probably not new to the lake. It is common in most aquatic systems in Maryland and other areas with warm climate. The difference this year is that fish were stressed and vulnerable to an infection. Aeromonas hydrophila is described as a "saprophytic" meaning it becomes pathogenic when fishes are physiologically unbalanced, nutritionally deficient or there are other abnormalities which allow opportunistic organisms to invade.
Where did the bacteria come from? There is not a specific source for the bacteria. It is considered a common bacteria in aquatic systems (from freshwater to salt water), mainly affecting cold blooded critters (NOT a common human pathogen). Many kinds of bacteria are found in aquatic systems and are part of the natural system.
Is there any monitoring for any bacteria in Deep Creek Lake? There are different measures for acceptable bacteria levels depending on the designated uses of the water. Deep Creek Lake is not a drinking water supply. It is a hydroelectric generating impoundment and a water based recreational resource. The only bacteria monitored in recreational waters is E. coli which is considered the standard indicator for contaminated water. The Garrett County Health Department monitors the amount E. coli bacteria at numerous places around the lake each month from April through September.
How much bacteria is in the water? Data from the Garrett County Health Department indicates that E. coli counts at all data points on Deep Creek Lake are low and would not indicate unsafe swimming conditions.
Can my dog swim in the water? Yes. But dog owners are cautioned to prevent animals from eating dead fish that may be washed up on the shoreline. Floating dead fish should not be retrieved by pets either.
What can be done about the dead fish along the shoreline? With the warm air temperatures it will take a few days for the fish to decompose and disappear leaving rotten fish odors. Avoid direct contact with dead fish. If possible, dead fish should be scooped up with a shovel and buried under several inches of soil somewhere away from human activity. If the fish are left to rot on the shoreline, sightings of eagles, raccoons, crows or bears may become more commonplace.
How long will the situation last? No one knows the answer to that question. Cooler weather should alleviate the conditions as more normal water temperatures will provide fish with suitable habitat, causing less stress. Once the fish are healthier they will be able to fight off the influences of the protozoan and bacteria.
Can I fish from our dock? Fishing is ok. Extra care should be taken to wash hands often and if in injury from a hook or spine should occur, wash the wound carefully with soap and water and keep the wound away from the lake water.
Can I eat the fish I caught in Deep Creek Lake? Fish not showing signs of disease are safe to eat, as long as they are thoroughly cooked.
If 1000 fish have been found dead along the shoreline in a little over 2 weeks time– are there any fish left in the lake? The DNR Fisheries Service biologists who manage the fishery don’t have an exact count of the number of fish in the lake but have made an educated guess that several hundred thousand fish live in Deep Creek Lake. The fish mortality from this event is a very small percentage of the overall fish in the lake.
My children are playing with the dead fish – is that a problem? Direct contact with dead fish should be avoided by everyone. Remove dead fish from the shoreline with a shovel and bury them. Wash thoroughly after contact with dead fish.
Who should I call to report dead fish or turtles in Deep Creek Lake? The Frostburg office of MDE is taking calls during business hours for fish kill reports or algae blooms that occur more locally – Garrett County. That number is 301-689-1480. Or there are two telephone numbers to call anytime at 1-866-MDE-GOTO or 877-224-RBAY. If the message recording does not come on, hang up and call again. These numbers are both used for reporting of fish kills and algae blooms anywhere in Maryland and late summer is a busy time for these environmental situations