Human fishing seen changing fish balance

VANCOUVER, British Columbia, Feb. 18 (UPI) -- A decline in predatory fish and increase of forage fish proves humans are "fishing down the food web," affecting global ecosystems, Canadian researchers say.

Researchers at the University of British Columbia, surveying more than 200 marine ecosystems around with world, say predatory fish such as cod, tuna and groupers have declined by two-thirds in the last century while forage fish such as sardine and anchovy have doubled in the same period, a UBC release said Friday.

They said 54 percent of the decline in predatory fish populations took place in the last 40 years.

"Overfishing has absolutely had a 'when cats are away, the mice will play' effect on our oceans," Villy Christensen of UBC's Fisheries Center said. "By removing the large, predatory species from the ocean, small forage fish have been left to thrive."

While an increase in forage fish amounts to more fish production, Christensen cautioned that the lower food web is more vulnerable to environmental fluctuations.

"Currently, forage fish are turned into fishmeal and fish oil and used as feeds for the aquaculture industry, which is in turn becoming increasingly reliant on this feed source," Christensen said.

"If the fishing-down-the-food-web trend continues, our oceans may one day become a 'farm' to produce feeds for the aquaculture industry," he said. "Goodbye, wild ocean!"