The waters around the Vineyard are warming and scientists believe this may account for a shift in fish populations here. Scientists with the National Marine Fisheries Service and their science center in Woods Hole recently released the results of an 18-month study that examined 40 years of fisheries data and the movement of more than 30 species.

Titled Changing Spacial Distribution of Fish Stocks in Relation to Climate and Population Size on the Northeast United States Continental Shelf, the report was published Oct. 30 in the Marine Ecology Progress Series. The report found that the disappearance of some fish in area waters may not be entirely due to overfishing; climate change is playing a part.

While the study focuses principally on federal waters in the Atlantic, it touches on some species of fish that used to swim in Vineyard waters, and are no longer here.

“The Northeast United States continental shelf ecosystem has experienced a consistently warm period in the last 10 years and a rebuilding of many overfished stocks, presenting an opportunity to reexamine the links between distribution, warming, and population abundance,” the report says.

Atlantic mackerel, which used to be abundant in the spring around the Island and is now quite scarce, was one of 36 fish stocks reviewed in the study. Twenty-four of them, including pollock, cod, haddock, hake and all the flounders, appear to have moved northward and into deeper water.

Janet A. Nye, a postdoctoral research associate with the Northeast Fisheries Science Center in Woods Hole, confirmed that many species of fish that used to be abundant south of Cape Cod and off New York are no longer abundant. “It has always been hard to determine whether it is climate change or overfishing. Cod are very hard to study, as their range has contracted. They don’t occupy the area they used to,” she said, adding:

“During the last 40 years, many familiar species have been shifting to the north where ocean waters are cooler, or staying in the same general area but moving into deeper waters than where they traditionally have been found. They all seem to be adapting to changing temperatures and finding places where their chances of survival as a population are greater.”

Overfishing plays a part in the size of fish populations offshore. However, the study follows the premise that even when fish stocks are in decline, there is a central location that doesn’t change. While the numbers may vary, the core biomass of the fish should have a specific location from decade to decade if the water temperature doesn’t change. Ms. Nye, the lead writer of the report, said the study looked at where that core location has been over the years. “The center of the population of fish should stay the same,” she said, no matter how big the population. However in this study, the scientists found the center of fish stocks moved northward and offshore toward cooler waters.

William J. Overholtz is a senior analyst with the National Marine Fisheries Service and a co-author of the study. For 25 years he has studied mackerel. The results of his work and the work he did within the study strongly suggest that mackerel may have moved to cooler waters. This is a significant development for the Island community which once depended on mackerel as a primary staple food. Fishermen once landed mackerel by the boatload. Today, mackerel pass off Aquinnah in the spring headed north as part of an annual migration. The fish don’t stick around long, and mackerel season is short, a fraction of what it used to be.

Mr. Overholtz said the center of the mackerel population in the winter and spring used to be in the waters off Hudson Canyon and off Cape Hatteras. “It appears they have progressively moved north and out to Georges Bank,” he said.

That shift is intriguing because Atlantic mackerel used to prefer deeper water to the south, but due to warming water they have shifted to Georges Bank and they are now swimming in shallower water. This leads to the interesting observation that warming water temperatures may be driving some species of fish out of their normal habitat into areas that may not necessarily be as suitable.

Pollock is another fish once abundant in these waters. The late West Tisbury police chief George Manter once recalled to the Gazette his memories of fishing for pollock with a rod and reel off the Menemsha jetties in the winter. The thought of catching a pollock from the shore is unheard of today. Similarly, haddock was once abundant in Muskeget Channel, where commercial draggers plied their trade. Edgartown fisherman Turtle Lawry would go out in his dragger and catch thousands of pounds of haddock.

Today both pollock and haddock are considered overfished, although haddock is showing signs of recovery on Georges Bank.

Not a single fish was caught or evaluated for the purpose of the recent study. The report was based on documented fish surveys in the past by two NOAA research vessels: the 155-foot Delaware II and the 187-foot Albatross IV. Both vessels work out of Woods Hole. Each spring and fall, these boats go out and survey the seas, sampling areas from the Gulf of Maine to waters south of here.

The Albatross IV has since been replaced by the larger and more modern Henry B. Bigelow, a vessel that was launched in 2006 and built at the same shipyard in Mississippi as the Vineyard ferry Island Home.

“Many of the fishes in the present study migrate up and down the East Coast of the United States in response to seasonal changes in temperature. However, as the temperature regime warms, cold-water species may not migrate as far south in the winter; thus, we would observe a poleward shift in distribution when the species are sampled in the spring,” the report says.

The report suggests that the long-term impact of climate change could be harmful to many species, cautioning, for example, that fish eggs hatched in water that is too warm are more likely to die. Temperature change also can affect currents, the abundance of predators and the availablity of bait, or food.

Ms. Nye said she believes the work is only a start; there is plenty of room for more study, she said.

A paper was recently written about the impact of climate change on the North Sea fisheries in waters off Alaska. “The hope is that the scientists will look further at climate change, look more closely at each species and see if we can incorporate these concerns into our population models,” Ms. Nye said.

She said it would be great to be able to predict where fish will be in 50 years, using climate models.