Cold weather the likely culprit of massive fish kill in December

February 28, 2011|By Candus Thomson, The Baltimore Sun

Cold weather was most likely the cause of December's massive fish kill in the Chesapeake Bay, the Maryland Department of the Environment reported.

About two million fish — mostly juvenile spot 3 to 6 inches long — washed ashore in Calvert County, near the Calvert Cliffs nuclear power plant, Annapolis, Sandy Point State Park, Poplar Island south of Kent Island, the Honga River in Dorchester County and Tangier Sound. No other fish kills were reported after that single incident.

Tests on fish tissue showed no environmental contamination, said MDE spokesman Jay Apperson.

That finding and the data collected on water quality and water temperatures, the historical evidence of similar fish kills, what scientists know about the characteristics of the fish that were involved, all lead to the conclusion that the fish kill was caused by cold-water stress, Apperson said.

The bay's average surface-water temperature in late December — 32.9 degrees — was the coldest in 25 years, according to state records. Historical lows were recorded at 13 locations on the bay, from the mouth of the Elk River to Rock Hall and Kent Island to Point Lookout.

Spot have little tolerance for temperatures below 35.6 degrees.

Winter-related kills happen less frequently than summer events. Twenty million spot died in 1976 and again in 1980. Both of those kills ranged from Baltimore harbor to Solomons.

The kill is not likely to upset the balance of nature in the bay. The Department of Natural Resources 2010 survey of the spot population showed the fourth-largest juvenile class in 33 years.

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