Chesapeake Bay News

In January 2011, The Maryland Department of the Environment began 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.

According to Maryland Department of the Environment, preliminary monitoring results showed that water quality in the area appeared to be acceptable. Additional water quality monitoring results were being analyzed.

The affected fish were almost exclusively juvenile spot fish, three-to-six inches in length. MDE first received reports of dead fish in early January. The fish kill appeared 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 (4 to 5 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.

A recent DNR survey showed a very strong population of spot in the Bay this year. An increased juvenile population and limited deep water habitat would likely compound the affects of cold water stress.

Large winter kills of spot have occurred at least twice before in Maryland. In late January 1976, records show that about 15 million spot died of winter stress in the bay. A smaller number died in January 1980. Maryland experiences still smaller fish kills caused by cold water stress every few years.

MDE has advised that anyone who touches dead fish should take precautions such as washing hands. Residents can bury dead fish, but the tides, wildlife and natural decomposition should dispose of the fish.

MDE encourages anyone with information on fish kills to call 1-866-MDE-GOTO.

source: MDE

The Maryland Department of the Environment (MDE) and the Department of Natural Resources (DNR) are asking the public to watch for and report any diseased, dying, or dead fish on the Monocacy River. Although no dead or dying fish have been reported so far this spring, the agencies are investigating springtime fish health and mortality.

“Public input is important in helping state agencies to respond quickly and gather meaningful data,” said DNR Fisheries Western Region Manager John Mullican.

Last May an angler reported a fish kill in the upper Monocacy involving mostly adult smallmouth bass and sunfish. It is uncertain if this mortality was related to other springtime fish kills in the Potomac River watershed since 2002.

A single cause for the fish kills has not been identified; however, investigations suggest that fish are subjected to multiple stressors including contaminants; damaged skin, gills and internal organs; parasites, spawning injuries and stress. DNR has also discovered a high prevalence of intersex in some species, most notably smallmouth bass. Environmental and contaminant factors may also lead to immune suppression, which may make fish more susceptible to bacterial infections. Possible causes of contamination include agricultural chemicals (pesticides and antibiotics), urban runoff, prescription medicines and personal care products.

If you find dead or dying fish in the Monocacy or Potomac River, please contact the Maryland Safety and Environmental Hotline (877) 224-7229 or the DNR-Fisheries Service at (301) 898-5443 with the time, date, location, fish species, and approximate number of affected fish. Photographs and a description of any unusual behavior or water conditions are also helpful.

This information is provided as a public service of the Maryland Department of Natural Resources. www.dnr.maryland.gov