...not fish! - The kinds of fish available for your dinner table will change radically in the near future, thanks to global warming. When you next go to the store to buy fish, you may be in for some surprises?your favorite kinds may simply not be available any more. Or there may be nothing there at all, since the recent massive flooding of cities and farms in the Mississippi River basin has washed nitrogen fertilizer into commercial fishing areas of the ocean, causing "dead zones" where no fish can live.
Record-setting dead zones in the Gulf of Mexico and Chesapeake Bay appear likely this summer. Researcher Donald Scavia predicts that the Chesapeake Bay, which is about 200 miles long on the East Coast and stretches from Maryland to Virginia, and supports thousands of species of plants, fish and animals, will have the highest oxygen-depriving dead zone on record, covering between 8,400 and8,800 square miles along the Louisiana-Texas coast. Scavia says, "The growth of these dead zones is an ecological time bomb. Without determined local, regional, and national efforts to control them, we are putting major fisheries at risk." The way to avoid these dead zones is to reduce the amount of fertilizer flowing into the water?but can we convince farmers to either put up barriers or stop fertilizing their fields? This project, like the rebuilding of the levies in Louisiana, may be one that needs to be done by the federal government.
A detailed analysis of data from nearly 50 years of weekly fish-trawl surveys in Narragansett Bay and adjacent Rhode Island Sound has revealed a long-term shift in species composition, from vertebrate species (fish) to invertebrates (lobsters, crabs and squid). In addition, smaller, warm-water species have increased while larger, cool-water species have declined.
Oceanographer Jeremy Collie says, "This is a pretty dramatic change, and it's a pattern that is being seen in other ecosystems?" He notes that while most of the changes have occurred slowly, an abrupt change took place in 1980 and 1981 when species like winter flounder and silver hake declined and species including butterfish and bluefish increased.
"While we're catching more fish now, we?re also catching smaller fish," says Collie, "and that corresponds with how the preferred temperatures of the fish here have changed. The fish community now is dominated by warm-water adapted species compared with what we started with, and fish that live in warmer water are smaller." Collie adds that fishing may also be a factor in the decline in fish size, since fishing removes the largest individuals from a population while leaving the smaller ones. However, he believes that climate is "the dominant signal." Sea surface temperature in the area of the trawls has increased by 2 degrees Centigrade since 1959, and the preferred temperature of the fish caught in the trawls has also increased by 2 degrees C. He says, "That seems to be direct evidence of global warming. It's hard to explain any other way."
So next time you go to buy fish, expect some surprises.
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