Marine biologist outlines perils of over-fishing during URI lecture
Drastically reduced populations of blue fin tuna, sharks and other large fish predators indicate that the world’s oceans are in trouble and must be more carefully managed, a Canadian marine biologist said recently at the University of Rhode Island.
Noting that oceans produce 50% of the oxygen humans breathe – and absorb 40 to 45% of the carbon dioxide humans produce – Boris Worm, a professor at Dalhousie University in Halifax, Nova Scotia, called for reduced fishing to protect marine biodiversity. He also condemned wasteful practices, like shark finning.
Since the 1960s, fish diversity has declined, Worm said. Random surveys of 50 fish types indicate fewer species throughout the world. As biodiversity declines, he said, the ocean’s ability to produce food and filter water also drops.
Bluefin tuna stocks, for example, have declined 70 to 80%, Worm said, and their range has shrunk “to a fraction of what it once was.” Once common off the west coast of Africa, they are no longer found there, he noted. On land, when the range of carnivores like grizzly bears, wolves and large cats shrinks, they become vulnerable to extinction.
“Ocean predators are in no way different, Worm said.
Although climate change, pollution and habitat destruction contribute to declining fish populations, commercial fishing is the leading cause, according to Worm. Large fish populations, like tuna and marlin, are the first to collapse, leaving a less productive, less resilient and less predictable ecosystem with fewer and smaller fish. Not only is a major food source reduced, he added, but so is the ocean’s ability to clean water. A drastic decline in Chesapeake Bay oysters, for example, has made the bay more vulnerable to algal blooms, Worm said.
“It’s upon us to change that trend,” he told the audience, citing several examples of successful fisheries management.
Haddock on Georges Bank collapsed in the 1960s due to foreign fishing, he observed. The problem was temporarily solved with the extension of U.S. waters from 12 to 200 miles, but then, government incentives produced a second wave of over-fishing in the 1980s.
Since then, however, stricter regulation has increased the estimated weight of mature haddock in the area from 20,000 to 120,000 metric tons, he noted. In recent years, fishermen have benefited as the catch increased without stressing haddock stocks.
Worm also pointed to a New Zealand lobster program that provides incentives for fishermen to support conservation. Traditional fishing restrictions set a total annual catch quota. Anyone can fish, but once the combined catch of all fishermen reaches the quota, the fishery is closed.
New Zealand, however, restricted new entrants and granted individual fishermen a percentage of the quota that allows them to fish without fear of having the fishery closed. In addition, the percentage is their property, which can be transferred or sold, encouraging them to support conservation because the larger the lobster population, the more valuable their share.
Worm also urged audience members to support the Shark Protection Act.
Shark fins are a delicacy used in an Asian soup. They are so valuable, fishermen in Hawaii, Nova Scotia and elsewhere, cut them off and then discard the rest of the fish. The legislation, which passed the U.S. House in March 2009 and is pending in the U.S. Senate, would pressure other countries to join the U.S. in banning the practice. Both R.I. Senators Jack Reed and Sheldon Whitehouse are co-sponsors.
Worm also urged consumers to learn more about their seafood choices from www.seafoodwatch. org, a service of the Monterey Bay Aquarium in California.
In response to a question, Worm said he is optimistic that the oceans can be protected. Major change is possible, he noted, citing Germany’s drastic reduction in carbon dioxide emissions through solar power incentives.
“It can be done. It’s a choice,” he said. “We can be inert, or do something.”