A BOOM in shark fishing is threatening the ecological balance of the oceans, say experts meeting in Rome this week.
The UN Food and Agriculture Organization (FAO) says the world鈥檚 catch of sharks and their relatives, skates and rays, jumped from about 617 000 tonnes a year in 1985 to more than 730 000 tonnes in 1994. And for every shark caught deliberately, at least two more are killed by accident, mainly by shrimp and tuna vessels.
The FAO predicts that the catch will grow further. As traditional fisheries are depleted, fishermen will switch to sharks, while economic growth in China will boost the price of shark fins used to make soup.
Advertisement
No one knows what impact this will have on marine ecosystems, as shark fisheries are largely unstudied and unregulated. A report released last week by the Center for Marine Conservation in Washington DC, and TRAFFIC, the wildlife trade monitoring arm of the World Wide Fund for Nature, says that 鈥渓ittle effort has been made to collect even the most basic kinds of fisheries information鈥�. FAO member states are to discuss ways of improving the collection of data during this week鈥檚 meeting.
The TRAFFIC report notes that sharks are becoming harder to find, and are caught at ever younger ages. Yet only the US, Australia and New Zealand impose quotas on shark fisheries. Britain may ban fishing for basking sharks this year, but has no other controls-even though stocks of the piked dogfish or 鈥渞ock salmon鈥�, popular in fish and chip shops, appear to be falling. 鈥淧eople don鈥檛 care about sharks,鈥� says Sonja Fordham of the Center for Marine Conservation, an author of the report.
Predators are often important in stabilising prey populations, which for many sharks may include commercial fish. But there has been too little research to say how the killing of sharks affects marine communities, Fordham says. She suspects the effects of removing sharks could be profound. 鈥淲hen big sharks were fished out off Florida in the 1980 there was a huge, unexpected increase in stingrays,鈥� she says.
Fordham says sharks are especially vulnerable to overfishing because they grow and reproduce slowly, and so take a long time to recover from depletion. Data from Norway in the late 1940s show that it took only seven years of fishing the porbeagle shark before its numbers fell too low to support a fishery. 鈥淭hey still haven鈥檛 recovered,鈥� says Fordham.
Sam Gruber, a shark biologist at the University of Miami, adds that depleted shark populations can easily be wiped out by catastrophic events such as epidemics or sudden shifts in water temperature. But he says that overfishing is hard to avoid, given the poor state of current knowledge. 鈥淲e have no good information on population sizes, and we may never have it, because there isn鈥檛 the money in shark research.鈥�
