Inbreeding in Long Island's Winter Flounder: Loss of Genetic Diversity in Fish

Fish are a huge resource for coastal communities. They provide a valuable source of protein and can be sold for profit. Yet as we continue to plumb the depths of the sea, fisheries management is becoming more important than ever. Now, scientists have discovered something that fisheries have failed to take into account in the past and may affect the number of fish available in the future--inbreeding in fish populations.

Genetic diversity is important in wildlife. It allows species to cope and adapt in their environment, resisting diseases or developing new traits that can give them an edge when it comes to a shifting climate or other changes. It turns out, though, that fish are at risk for losing this diversity--at least when it comes to the winter flounder in Long Island's bays.

In order to examine the health of the flounder fishery, researchers examined fish in six bays of Long Island. They extracted genomic DNA from the fins of 267 young of the year winter flounder caught over a period of several months. They then used 11 polymorphic microsatellite loci to test for genetic diversity.

In the end, the scientists found that the effective number of breeders in each bay was below 500 fish. This suggested that the spawning populations of this historically common fish are now relatively small in the area.

"While documented to occur in freshwater fish, inbreeding in marine fish is generally not a serious concern because of their perceived ability to move through larger areas to find mates and, historically anyway, their much larger populations sizes making it unlikely they would spawn with relative," said Shannon O'Leary, lead author of the new study, in a news release.

It seems, though, that inbreeding is a problem in marine fish and a factor that should be considered when it comes to fisheries management. Inbreeding has been linked in the past to lower survival and reproductive rates along with lower resistance to disease and environmental stress. This means that inbred fish could potentially be pushed to a population collapse if managers aren't careful.

"We are just beginning to realize that marine fish frequently exist as a series of smaller subpopulations as opposed to one large, well-mixed and widely distributed population," said Demian Chapman, leader of the research team, in a news release. "The evidence of inbreeding we have found supports the new paradigm. The number of effective breeders in each bay is also alarmingly low and argues for strong fisheries management and habitat restoration initiatives to rebuild winter flounder populations in Long Island bays."

The findings are published in the journal PLOS One.