SpruceRoots Magazine - June, 1998

FISHING DOWN THE FOOD WEB by Ian Lordon

Stock sustainability issues are not unique to the islands. A landmark study captured widespread media attention earlier this year with its unsettling depiction of declining global fishing stocks.

The study, the work of an international team of scientists led by UBC professor Daniel Pauly, clearly demonstrates that the world's most valuable fishing stocks are suffering long-term damage and current fishing practices are hampering their recovery.

"The fisheries, as we manage them now, are not sustainable," Pauly says. "Present trends will lead to widespread collapse."

Pauly and his fellow researchers assigned trophic levels to hundreds of marine species based on their position in the food chain. Trophic levels rate that position on a scale of 1 to 5. Planktonic algae, at the base of the food chain, has a trophic level around 1, while large predators like sharks, tuna, or swordfish are at level 4.

Next, they collected worldwide catch statistics from the past 40 years and calculated the average trophic level from each year's harvest.

The overall trend that emerged showed a gradual but steady depletion of larger, prized, predatory fish and a growing reliance on smaller species. Pauly calls this "fishing down the food web" and says the downward shift eventually manifests itself on dinner tables and restaurant menus.

"Americans wouldn't eat squid before," he says. "It was used as bait and now Americans are eating bait. It has all kinds of fancy Asian names, but it's bait."

Although a growing appetite for bait among consumers may seem harmless, Pauly says it is accompanied by certain negative implications. First, it implies larger stocks are no longer abundant, and second, those that remain must now compete with commercial fisheries for the smaller species they feed upon. Canada's east coast, where fishermen turned their attention to shrimp once cod stocks were wiped out, is a classic example.

"Cod feed on shrimp. If you remove the shrimp, how will the cod recover?" Pauly asks, and then notes once the shrimp are gone..." It's mud, and that's when you hit the wall."

Without a sustainable and global approach to fisheries management, Pauly suggests the best method to preserve larger species of fish is to establish marine protected zones where fishing of any kind is completely banned.

"There's no way the present fisheries management can restore big fish," he says. "But nature will do that for us in protected areas."

SpruceRoots Magazine - June, 1998