MDE investigates large fish kill in Chesapeake Bay

The Maryland Department of the Environment is investigating a fish kill in the Chesapeake Bay in which an estimated two million fish have died. Natural causes appear to be the reason for the deaths of the fish. Cold water stress exacerbated by a large population of the affected species (juvenile spot fish) appears to be the cause of the kill.

Preliminary monitoring results show that water quality in the area appears to be acceptable. Additional water quality monitoring results are to be analysed. The affected fish are almost exclusively juvenile spot fish, three-to-six inches in length. MDE first received reports of dead fish last week. The fish kill appears to be centered on the bay from the Bay Bridge to Poplar Island.

Spot may have difficulty surviving in colder temperatures, and the species’ susceptibility to winter kills is well-documented. A rapid drop in water temperatures apparently caused cold water stress. Surface water temperatures in the bay have reached about 0.5 degrees Celsius according to Md. Department of Natural Resources Bay Program monitoring data, which is the coldest December recording in 25 years of monitoring.

Adult spot normally leave the bay during winter, but juveniles occasionally winter over in the area. Bottom water temperatures near their lower thermal limit (four to five degrees Celsius) are not uncommon in the bay during winter. Juvenile spot, overwintering because of a mild early winter, may be susceptible to fish kills due to sudden decreases in water temperature. Read more...

This blog is written by Martin Little The Aquaculturists, published and supported by the International Aquafeed Magazine from Perendale Publishers.