Whales have been implicated in the reduction of fishing stocks.© PhotoDisc

Whales and other marine mammals do not exploit fisheries to satisfy the bulk of their 600-million-tonne annual appetite, scientists told the International Whaling Commission yesterday.

The research is creating conflict in an already fractious environment, at a time when Japan and Norway have announced their intentions to increase whale captures. One of Japan's arguments for increasing 'scientific' whaling is to help determine how many fish the whales are consuming, while Norway is proposing to triple its annual minke whale catch, in part because of the animals' supposed effects on fisheries.

The study, carried out by Daniel Pauly and Kristin Kaschner of the University of British Columbia in Vancouver, is the first to map the overlap between marine mammals and fisheries across the world's oceans. The study used computer models to divide the oceans into 180,000 cells, overlaying what is known about the species found in each cell with fisheries' catch data.

The authors found that less than 1% of all food consumed by marine mammals comes from areas that overlap with fisheries.

"You cannot use the argument that whales compete with fisheries and therefore must be reduced in numbers," says Kaschner. "It's deeply flawed. They simply don't eat the same food in the same areas."

Japan has long made the argument that whale populations must be kept in check so that they do not turn into oceanic pests, depleting the fish on which humans rely.

"The paper, once and for all, shows that is not the case," says Kitty Block, an international lawyer for The Humane Society International. "We're at an all-time high of drift netting, long-line netting, gill fishing, trawling... these are human exploitation methods. It's nothing to do with the whales," she says.

However the Japanese delegates say the report is consistent with their own results, because it does show overlap between marine mammals and fisheries around Japan and Iceland.

Heated debate

The International Whaling Commission, whose annual meeting started on 19 July in Sorrento, Italy, placed a moratorium on commercial whaling in 1986. It has been divided ever since, with Japan, Norway and Iceland leading the pro-whaling contingent. Anti-whaling nations have accused Japan of buying the votes of developing countries, in part by persuading them that full-scale commercial whaling should be resumed to keep whales from swallowing up the stocks of commercial fisheries.

The authors admit that there are potential hotspots for the interactions between marine mammals and fisheries, which "will require much more detailed investigations to establish the true extent of the problem at hand". Such areas include the Benguela system off the coast of southwest Africa, where increasing populations of South African fur seals may affect hake stocks.

However the authors report that the most common type of conflict is likely to be one where fisheries have an adverse effect on a species of marine mammal, rather than the other way around. For example, in the Bering Sea, fisheries could have a negative impact on the endangered western population of Steller sea lions. 

University of British Columbia, Vancouver