Thousands of Atlantic menhaden – a baitfish that plays a key role in the South Atlantic ecosystem – were found washed up on the beaches in the south area of the Grand Strand on Tuesday and Wednesday, leaving S.C. Department of Natural Resources investigators trying to determine the cause.
From DeBordieu, a private community just north of Georgetown, northward to Pawleys Island, a rough estimate of 30,000 to 40,000 menhaden in the 6-to-8 inch range were spread along the beach and first spotted by beachgoers taking advantage of the unseasonably warm weather.
Researchers from the University of South Carolina’s Belle Baruch Institute for Marine & Coastal Sciences took ocean water samples from where the menhaden washed ashore at DeBordieu and found typical winter conditions in levels such as dissolved oxygen and salinity.
A reddish slick was noticed in the water near the beach that researchers found to be decaying fish matter from the dead menhaden.
When a fish kill occurs in the ocean, the culprit is often found to be an algal bloom such as red tide, widespread low levels of dissolved oxygen or, especially in the winter, colder-than-normal ocean water temperatures.
The testing ruled out an algal bloom and widespread areas of low dissolved oxygen, or hypoxia, and the water temperature is above normal thanks to the recent stretch of warm weather.
Mel Bell, Director of the Office of Fisheries Management for S.C. DNR, provided his agency’s theory on the kill.
“On Friday we had a new moon (which caused) real high high tides and real low low tides,” said Bell. “Probably what happened was a school (of menhaden) got in an area of water on a high tide, in a hole or depression, and at low tide they were trapped and depleted the oxygen in the water. Then, all the fish would suffocate.
“We don’t know for certain, but given the results of the water sample analysis and the tides, that’s probably the best working hypothesis. Then when the tide came back in, it washed the dead fish out and they washed up on the beach.”
Menhaden, typically found in large schools, are fragile fish that require highly oxygenated water and can easily succumb to low oxygen levels and cold water temperatures. The species is a favorite bait for fishermen.
“The thing about a school of menhaden, they are fish that are swimming constantly – a school of menhaden is a lot of fish consuming a lot of oxygen,” said Bell. “I can see where a school of menhaden can deplete the oxygen in a (confined) area.”
A similar kill of menhaden occurred last week at Masonboro Island, near Wilmington, N.C. In early January, 2007, a kill of menhaden occurred near Charleston at Folly Beach, but that event was attributed to cold water temperatures.
In all, Bell surmises the kill on the Georgetown County beaches was a simply a matter of Mother Nature at work and provided a winter treat for scavengers when food can be scarce.
“These things happen,’’ said Bell. “The crabs will be happy, the gulls will be happy. You could tell the gulls were definitely working it. (The menhaden) will get recycled into the ecosystem.”