Several cold weather fish kills have impacted the Mid Atlantic region during the 2011 Winter season.
Numerous fish kills occurred in North Carolina in December of 2010 thru mid-January 2011. From mid thru late December, several isolated cold stun events occurred. Most fish kills involved small quantities of fish in inland waterways.
In mid-January, much larger cold stun events occurred, including fish kills in Campbell Creek and other estuaries. In addition to spotted seatrout, inland cold stun events in North Carolina affected red drum, black drum, spot, mullet and menhaden.
As a result of "cold stun" fish kills that affected spotted seatrout, North Carolina closed coastal waters to commercial and recreational harvests of the species for an indefinite period . The N.C. Division of Marine Fisheries Director Louis Daniel issued a proclamation on January 12, 2011, implementing the closure.
According to the department, the action was taken in response to cold stun events in Rose Bay, Juniper Bay, Pungo River, Campbell Creek, Turnigan Bay, Spooners Creek and other waters. The intent of the closure is to prevent the harvest of vulnerable cold stunned fish, which may recover with warming temperatures. North Carolina's Spotted Seatrout Fishery Management Plan authorizes the Director to temporarily close harvest in the event of a cold stun event.
In addition to inland fish kills and cold stun events, large numbers of Atlantic croaker were reported to have washed ashore near Rodanthe during early January.
On January 5, 2011, The Maryland Department of the Environment announced that it was investigating a fish kill in the Chesapeake Bay in which an estimated two million fish died. According to MDE, cold water stress appeared to have caused the fish kill, which affected a large population of the juvenile spot fish.
The spot, mostly three-to-six inches in length washed up on beaches in enormous quantities following a cold snap in early January. The fish kill occurred in the from the Bay Bridge to the Mid-Chesapeake Bay.
The species' susceptibility to winter kills is well-documented. The cold water stress is thought to have occurred as a result of a rapid drop in water temperatures. Surface water temperatures in the bay dropped to around 0.5 degrees Celsius in December, which was the coldest recording for the month 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.
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. Minor fish kills caused by cold water stress happen in Maryland waters every few years.
Meanwhile, on Maryland's Eastern Shore, less obvious fish kills were occurring. On several occasions residents have reported seeing gizzard shad, also known as "mud shad" stunned or dying in the shallows during periods of sudden water temperature drops. The fish were reported to be spread over a large area, making mortality estimates difficult.
Several creeks and estuaries have seen dramatic increases in numbers of bald eagles which have moved in to feed on stunned or dead fish. In some sheltered areas, gizzard shad have congregated in large numbers, presumably seeking warmer water.