Skip to Content Accessibility Information

Maryland Department of the Environment

Department of the Environment fish kill investigation continues

Media contact:

Jay Apperson


Department of the Environment fish kill investigation continues

Department investigating new but unconfirmed information relating to case, as precaution anglers advised to avoid eating fish from area as investigation continues

Baltimore, MD (November 14, 2015) – The Maryland Department of the Environment is continuing its investigation of a fish kill in the upper Middle River and several of the river’s tributaries in Baltimore County.

The Department has become aware of citizen concerns relating to a possible discharge into the waters in the area of the fish kill. The Department will investigate these concerns. No information relating to these concerns has been confirmed by the Department. As a precaution, the Department recommends that anglers avoid eating fish from the area of the fish kill as the investigation continues.

The Department estimates more than 100,000 fish have died in the waterways the past several days. The preliminary results of the Department’s investigation show the cause of the fish kill to be a strain of algae that produces a toxin that is lethal to fish. The toxin kills fish by inhibiting oxygen uptake through their gills. There is no indication that the toxin is harmful to people or to other animals.

The waterways affected include Norman Creek, Hopkins Creek, Dark Head Cove and the upper Middle River. The fish affected include largemouth bass, yellow perch, bluegills, crappies, chain pickerel, pumpkinseed sunfish, carp, killifish and Atlantic menhaden. The Department of the Environment is providing information on the fish kill to the Maryland Department of Natural Resources and the Baltimore County health department.

The Department of the Environment received several reports of the fish kill beginning Monday morning. The Department went to the site to investigate Monday, Tuesday and Thursday. The Department obtained water samples and fish tissue samples. An analysis of the water samples showed the presence of the dinoflagellate Karlodinium veneficum, with cell counts high enough to produce the toxin. The release of the toxin appears to have been exacerbated by large amounts of the algae dying off simultaneously. Subsequent analysis shows that the cell count levels of the algae appear to be diminishing.

Blooms of this type of algae are typically seen in the late spring or summer months. The warm weather this fall might have allowed the algae to survive and grow, and recent drops in the water temperature might have caused the algae to die.

Excessive levels of nutrients such as nitrogen and phosphorus in the water can lead to algae blooms. Reducing nitrogen and phosphorus pollution from all sources is at the heart of Maryland’s blueprint for Chesapeake Bay restoration.

This week’s fish kill appears to be the largest in Maryland this year. There have been about 80 smaller fish kills this year in Maryland, caused by factors such as low dissolved oxygen levels in water, localized pollution and the discarding of dead fish.

The investigation into this week’s fish kill has not shown any confirmed evidence of any chemical pollution as a cause. The investigation is continuing. Water samples have been sent to the University of Maryland for further analysis, including confirmation of the presence of the toxin.

Anyone with information on this or any other fish kill or with other concerns on environmental matters involving the Chesapeake Bay or its tributaries should call the Bay environmental hotline at 877-224-7229.

# # #