Fish-Kill Events

Large die-offs of fish or other marine organisms occasionally take place worldwide, including in Chesapeake Bay, its tributaries, and Virginia's coastal ocean. Causes of fish-kill events include suffocation during periods of low oxygen, stress from unusually warm or cold water, toxins ingested or encountered during harmful algal blooms, disease, and spills of oil or other contaminants. Accumulations of dead fish are also sometimes caused by the dumping of bycatch from commercial fishing nets.

Researchers at the Virginia Institute of Marine Science are often called on by other state agencies to help determine the magnitude, cause, and consequences of fish-kill events, but this can be difficult. The organisms that are available for study are typically already dead and decaying, making it difficult to isolate the cause of their mortality. Currents and waves may also cause dead fish to accumulate in areas away from where they died, hampering efforts to detect the source and nature of any causative agent.

A few dead fish washed up on a beach is not uncommon and is of little cause for concern. However, if you observe large numbers of dead fish on the shore or in the water, please first contact the Virginia Department of Environmental Quality (DEQ), which has initial responsibility for investigating fish kills in Virginia waters.

Notable fish-kill events, past and present, are detailed below.

Federal researchers investigate dolphin deaths

Researchers with the National Marine Fisheries Service have determined that a cetacean morbillivirus is causing unusually large numbers of dead dolphins to wash up on mid-Atlantic beaches.

VIMS researchers investigate fish kill

Researchers at the Virginia Institute of Marine Science continue to investigate last week's fish-kill event, in which observers reported hundreds of dead and dying adult menhaden in several Peninsula waterways. The researchers have so far discovered no conclusive evidence as to the cause of this relatively small event.