BALTIMORE, Jan. 5 (UPI) -- Maryland officials say they are investigating a large fish kill in Chesapeake Bay, but suspect cold temperatures, not water-quality issues, were responsible.
The Maryland Department of the Environment estimated 2 million fish have been reported dead in the upper bay, The Baltimore Sun reported Wednesday.
Bay water quality tested as acceptable and biologists said they believe "cold-water stress" was the probable cause of the mass kill, department spokeswoman Dawn Stoltzfus said.
The dead fish are primarily adult spot with some juvenile croakers, she said, and spot are susceptible to colder water and normally leave the upper bay by this time.
Water temperatures plummeted in late December to 36 degrees, a near-record low for that time of year, Stoltzfus said.
Large winter kills of spot have been seen at least twice before, she said, with about 15 million dying in early 1976 and a smaller number in 1980.