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Published April 7, 2009 10:10 AM

Depletion of Prey Fish may be Starving the Oceans

Rome, Italy -- Scientists are finding evidence of widespread malnutrition in commercial and recreational fish, marine mammals, and seabirds because of the global depletion of the small fish they need to survive, according to Oceana's new report, "Hungry Oceans: What Happens When the Prey is Gone?" These "prey fish" underpin marine food webs and are being steadily exhausted by heavy fishing, increasing demand for aquaculture feed, and climate change.

"We have caught all the big fish and now we are going after their food," said Margot Stiles, marine scientist at Oceana. "Until recently it has been widely believed that prey fish are impossible to overexploit because their populations grow so quickly. We are now proving that untrue as the demands of commercial fisheries and aquaculture outpace the ocean's ability to provide food for us and itself."

Hungry Oceans finds that 7 of the top 10 fisheries in the world target prey fish. These fisheries have emerged as populations of bigger fish have become overexploited and depleted. The report concludes that the impacts of fishing activity over the past decades has been so great that the nearly all prey fisheries now cannot withstand increased fishing pressure. Hungry Oceans also finds that aquaculture is increasingly the driver behind overfishing of prey fish, as salmon, tuna and other carnivorous farmed fish become the fastest growing seafood products in the world. Changing ocean temperatures and currents caused by climate change also make prey fish populations more vulnerable.

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Hungry Oceans coincides with the release today of the biennial State of the World Fisheries and Aquaculture report by the U.N. Food and Agriculture Organization (FAO). The FAO concludes that 80% of all marine fish stocks are currently fully exploited, overexploited, depleted, or recovering from depletion; including stocks of the 7 largest prey fisheries. Very few marine fish populations remain with the potential to sustain production increases, and more have now reached their limit than ever before.

Impacts

The future of valuable commercial and recreational fisheries is threatened by the loss of prey fish, especially those that are currently rebuilding from historic depletion. Hungry Oceans identifies bluefin tuna, striped bass, Pacific salmon, and Pacific halibut as key species dependent on prey fish.

"We're constantly making life difficult for endangered species from seabirds to whales, and going hungry is not going to help. Valuable fish like bluefin tuna are struggling, and we can't expect the fishery to recover when we are stealing their food supply. By taking food from the tuna we could end up hungry ourselves" said Stiles.

Marine mammals and seabirds also depend on access to prey fish for their daily survival and for their young, including blue whales, humpback whales, penguins, and terns. Even species protected under national and international laws are experiencing food shortages.

Solutions

More responsible management is needed to prevent predators from going hungry. Hungry Oceans proposes a series of measures including a moratorium on new fisheries targeting prey species, conservative catch limits for existing fisheries, first priority for the needs of ocean predators, and stopping fishing for prey in predator breeding hotspots.

"Fisheries managers simply take prey for granted despite their critical role in the ecosystem," said Stiles. "We need to act responsibly when taking prey from natural predators, with our eyes open to the consequences for the ocean and for our own supply of seafood."

This article is reproduced with kind permission of the Oceana
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