The Maryland Department of the Environment is investigating a large number of fish deaths in the Potomac River, a phenomenon known as a “fish kill.”
Scientists believe the fish kill is likely the result of what’s called a “summer turnover,” when warmer water from the surface and cooler water from lower down suddenly mix. When this happens, the cooler water with less oxygen rises, stressing the fish.
The water was measured at 94 degrees on Saturday, when the D.C. region was experiencing excessive heat. Fish need the dissolved oxygen in cooler water to survive.
Teams are collecting more water quality measurements, documenting the extent of the fish kill, identifying affected fish species and collecting fish for laboratory analysis.
Authorities said most of the fish have washed up near Sycamore Island, just south of Glen Echo Park, and that this occurred upstream of the Potomac Interceptor failure that sent millions of gallons of raw sewage flowing into the river.
Additionally, they say there is no evidence of a chemical spill or other pollution.
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