Menhaden Mystery: Mid-Bay Fish Kills Under Investigation

Michael ONeil/ Facebook

A series of localized fish kills in the midsection of the Bay has Maryland Department of the Environment (MDE) leaders looking closely at each one.

MDE confirms to Bay Bulletin, hundreds of Atlantic menhaden between eight and 11 inches have washed up since early last week.

 Photo: Michael ONeil/ Facebook
Photo: Michael ONeil/ Facebook

MDE is investigating individual fish kills at Quiet Waters Park on the South River, the Severn River above Round Bay, Terrapin Park near the mouth of the Chester River on Kent Island, and the Patapsco River from the Key Bridge to Fort McHenry.

Michael ONeil posted photos on Facebook showing dead fish littered all over the beach Saturday at Terrapin Park.

Of the four affected areas, MDE believes the Terrapin Park and South River incidents were caused by stranding in tidal ponds. MDE spokesman Jay Apperson says in the case of Terrapin Park, the agency counted more than 50 dead fish in the tidal pond, many quite far from the intake canal. After the fish were stranded and died there, they likely washed out of the tidal pond and floated south to the Bay Bridge on the Eastern Shore side.

Apperson says MDE doesn’t know why the menhaden, typically an open-water fish that don’t maneuver well in confined areas, would have entered the tidal pond intake.

“The most likely scenario is that they were corralled by predatory fish and forced to enter the intake in order to evade predation.”

Then, Apperson explains, they probably became stranded when the tide went out and the water level dropped. Apperson tells Bay Bulletin, “Most of the fish examined have been dead a few days and show signs of contusions and scale loss.”

MDE is still investigating the cause of the fish kills in the Severn and Patapsco Rivers.

According to Apperson, water quality results in all four areas have been acceptable, and no other aquatic species seem to be affected. The dead fish count in each location has ranged anywhere from 30 to several hundred menhaden.

For perspective, menhaden travel in schools that can reach more than a million fish, so a few hundred is a small percentage. But any fish kill is cause for concern.

According to the Chesapeake Bay Program, menhaden are a critical link in the Chesapeake Bay food chain. In addition to being filter feeders that can filter seven gallons of water per minute, they also serve as a food source for striped bass, osprey, bald eagles, and other predators.

-Meg Walburn Viviano