for National Geographic News
Lobsters, crabs, squid, and other invertebrates are becoming more common while populations of bottom-feeding fish are plummeting, according to a long-term trawling study of Rhode Island's Narragansett Bay.
The study also shows that small, warm-water species have increased while larger, cool-water species have declined.
Scientists from the University of Rhode Island (URI) say rising sea temperatures linked to global warming is the primary cause of shifts in the abundance and types of species living in the bay and adjacent Rhode Island Sound (see map).
And "these types of changes are probably widespread," said lead author Jeremy Collie.
Ray Hilborn, a fisheries expert at the University of Washington in Seattle, said the results of the new study—and similar trends elsewhere—call for a retooling of fisheries management practices.
"These major changes in marine ecosystems are being recognized to be reasonably common, and the shift from groundfish to invertebrates such as crabs, prawns, and scallops has been seen in quite a few places," he said.
But so far, most fisheries management programs aren't keeping pace with the changes, Hilborn said.
"If the system has changed and stocks no longer can be maintained at the same population sizes—in effect replaced by other species—then we need to rethink what our targets are for these stocks."
Decades of Data
A founder of URI's Graduate School of Oceanography began the trawling surveys of the bay in 1959.
Several generations of researchers and students have kept up the work since then, and the survey now represents what may be the world's longest-running record of its kind.
"Many of the things you hear about the effects of warming are sometimes anecdotal, because people don't have the records of what was there before," study author Collie said. "We have the record."
SOURCES AND RELATED WEB SITES