The Middle River Watershed covers a 12-square-mile area with tributaries that feed into Middle River which flows south directly into the Chesapeake Bay. On Monday, November 9, several local residents noticed dead fish floating in Norman Creek. Word of the fish kill quickly spread. It was soon discovered that there was also a problem in Hopkins Creek and Dark Head Cove. Calls were immediately placed to the Maryland Department of the Environment. Over the next several days, (Monday, Tuesday and Thursday) investigators visited the various sub-watersheds. The investigators found more than 100,000 fish had died. These included large-mouth bass, yellow perch, bluegills, crappies, chain pickerel, pumpkinseed sunfish, carp, killfish and Atlanta menhaden. The representatives of the Maryland Department of the Environment notified the Maryland Department of Natural Resources, Fisheries Services.
Water testing was done to determine the cause of the largest fish kill on record in Baltimore in 2015. Tissue samples from the different types of fish were also collected and evaluated. The Department of the Environment determined the cause of the fish kill to be a strain of algae that upon its deterioration produces a toxin. This toxin is lethal to fish. The toxin kills fish by depleting the oxygen in the water and blocking the oxygen uptake through the fish gills. Reportedly, there is no known danger to humans. It has been determined that the surviving fish should be safe to eat. However, the Department of the Environment has issued fish consumption advisories for Maryland waterways.
The release of the toxin appears to have been intensified because large algae blooms were dying off at that point in time. By Thursday, the water samples showed a decrease in the cell count levels of the algae. Blooms of this type are usually experienced in these waters in warmer weather, specifically spring and summer months. The recent warmer temperatures this fall may be the reason for the algae to survive and grow. Then, upon the drop in water temperature, the algae died off.
Smaller fish kills were experienced approximately 80 times throughout 2015. These fish kills occur naturally throughout the seasons and are caused by various factors that dissolve oxygen in the water as well as uncontrolled pollution. Another problem that adds to the problem is the discarding of dead fish.
To date, there is no sign of any chemical pollution as a cause. However, the investigation is continuing. Water samples have been sent to the University of Maryland for further analysis. The Department of the Environment has asked anyone with information regarding any fish kill or other environmental concerns involving the Chesapeake Bay and its numerous watersheds to contact their hotline at 1-877-224-7229.