Narragansett’s ecosystem shake-up

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Move over Rhode Island reds; here come Rhode Island blue crabs. The ocean state’s Narragansett Bay appears to be well on its way to becoming a second Chesapeake Bay biologically. And scientists point the blame at global warming.

Records gathered during weekly fish trawls in the bay since 1959 constitute one of the longest consistent records of fish populations. University of Rhode Island researchers have mined the data and found that warm-water species have been increasing while cool-water species have dropped off, as the surface temperatures in the trawl area have risen by 3.6 degrees F. over that time.

In the process, the mix of organisms has shifted from predominantly bottom-feeding fish to crabs, lobster, and squid, while the remaining fish populations are more likely to be species that swim nearer the surface. Part of the change, the researchers say, cascaded as these higher-swimming fish began eating the plankton that otherwise would have fallen to the bottom to feed bottom-dwelling fish.

“This is a pretty dramatic change,” says Jeremey Collie, a researcher at the University of Rhode Island who led the study. He notes that similar patterns are emerging on Georges Bank – off the coast of Massachusetts – and other “continental shelf ecosystems.”

The net effect: What once was a cold-water estuary over time will more closely resemble southerly bays. The results appear in this month’s Canadian Journal of Fisheries and Aquatic Sciences.

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