Warming oceans make North Atlantic fish populations shift
3 Nov 2009, 1456 Hrs

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Washington, November 3 A new study has determined that about half of 36 fish stocks in the Northwest Atlantic Ocean, many of them commercially valuable species, have been shifting northward over the last four decades, all thanks to warming oceans.

The study was conducted by researchers from the National Oceanic and Atmospheric Administration (NOAA).

Janet Nye, a postdoctoral researcher at NOAA's Northeast Fisheries Science Center (NEFSC) laboratory in Woods Hole, Massachusetts, and the lead author of the study, looked at annual spring survey data from 1968 to 2007 for stocks ranging from Atlantic cod and haddock to yellowtail and winter flounders, spiny dogfish, Atlantic herring, and less well-known species like blackbelly rosefish.

Historic ocean temperature records and long-term processes like the Atlantic Multidecadal Oscillation and the North Atlantic Oscillation dating back to 1850 were also analyzed to put the temperature data into context.

"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," Nye said.

"They all seem to be adapting to changing temperatures and finding places where their chances of survival as a population are greater," she added.

They represented a wide range of taxonomic groups, and were known to be commercially or ecologically important.

The researchers looked at where the fish were caught and their biomass, or the estimated total weight of the population, in each year of the survey.

For each stock, they estimated the center of abundance, average depth, the range or area that the stock occupied, and the average temperature at which each stock was found.

They also took into account fishing pressures on the species over time, as well as natural cycles in ocean temperature.

The authors found significant changes in species distribution consistent with warming in 24 of the 36 stocks studied.

Ten of the 36 stocks examined had significant range expansion, while 12 had significant range contraction.

However, the temperature at which each stock was found did not change over time, suggesting that fish are moving to remain within their preferred temperature range.

"The fact that we see responses in many species consistent with what you would expect with warming, but in different types of species that have experienced different historical fishing pressure, suggests that we are already witnessing the response of fish to a warming scenario," Nye said.

"The community structure is changing from cool-water to warm-water fish species. These trends will likely continue," she dded. (ANI)

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