A new study from the University of British Columbia found that predatory fish such as cod, tuna and groupers have declined by two-thirds over the past 100 years while small forage fish such as sardine, anchovy and capeline have more than doubled in the same time period.
A team of scientists, led by Professor Villy Christensen of UBC’s Fisheries Center, used more than 200 marine ecosystem models from around the world and collected more than 68,000 estimates of fish biomass from 1880 to 2007. Their findings were presented at the American Association for the Advancement of Science (AAAS) Annual Meeting in Washington, DC.
The coinciding decline of predatory fish and increase of forage fish provides the strongest evidence that humans are “feeding down the food web.” The UBC team found that 54 percent of the decline took place in the last 40 years alone.
“Overfishing has absolutely had a ‘when cats are away, the mice will play’ effect on our oceans,” said Christensen. “By removing the large, predatory species from the ocean, small forage fish have been left to thrive.”
While the doubling of forage fish amounts to more fish overall, Christensen warns that a lower trophic-level 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,” said Christensen. “If the fishing-down-the-food-web trend continues, our oceans may one day become a ‘farm’ to produce feeds for the aquaculture industry. Goodbye, wild ocean!”
Christensen’s presentation was part of an experts’ panel to answer the question “2050: Will there be fish in the ocean?” The panel predicted that while there would be fish in 2050, it would consist mostly of the smaller variety.
Copyright © 2011 by Marine Science Today, a publication of OceanLines LLC