Winter flounder are inbreeding near several bays on Long Island, a trend that poses a further threat to the fish's survival, a Stony Brook University study has found.
Overfishing and habitat loss due to pollution have contributed to the decline of winter flounder in the region, but the new findings point to inbreeding as a contributing factor.
Researchers found that as the population of winter flounder has declined, the likelihood that fish with similar genetic compositions will mate has increased.
That's troubling, scientists say, because inbred fish tend to be weaker and less able to survive.
The Stony Brook study examined six bays along Long Island, from Jamaica Bay to Napeague Harbor, over a two-year period, ending in October 2011. Researchers found fewer than 300 winter flounder mature enough to reproduce in each of the bays studied.
Shannon O'Leary, the study's lead author, says that number should be at least 500 to ensure survival.
The fish stay within those bays, "so if you have populations that are very small, you're more likely to mate with your relatives," O'Leary said.
"In addition to things like high toxicity levels and low oxygen levels, if the fish are inbred, they're not going to be able to survive," she said. "It could be the straw that breaks the camel's back."
While inbred freshwater fish are common, the study is one of the first to document that trend in marine fish in U.S. waters.
"Previously, there was always the assumption that fish populations are large and they would never drop to levels where inbreeding could occur," O'Leary said.
There has been a steep decline in winter flounder off Long Island in recent years, said Tom Schlichter, of Southold, managing editor of The Fisherman magazine and a Newsday columnist.
"They used to be plentiful; they're not any longer," he said.
The New York Department of Environmental Conservation declined to comment on the study. "Thoughts on the implications for fishing or future regulations would be highly speculative," a department spokeswoman said.