Western Canada's sardine fleet returned with no fish this month. The loss of the fishery, normally worth CAN$32 million (US$30.7 million), took many by surprise. Yet researchers warned last year that it could happen.
There are still sardines off the US Pacific coast. But the vanishing of the Canadian fish is part of a process that could mean they all disappear for decades, says Juan Zwolinski of the University of California at Santa Cruz.
Pacific sardine populations fluctuate with water temperature. Colder water means fewer fish. Temperatures last fell in the 1940s, but heavy fishing continued, devastating the stock and ending fishing until sardines returned when waters warmed in the 1980s.
"We think this is set to happen again," says Zwolinski, who tracked the population over the past century. He found that sardines have reproduced less since waters cooled in the 1990s. Almost all eggs now come from fish born a decade ago, which are nearly gone.
What's more, acoustic results show that the fish have become smaller over the past decade, partly because of chillier water. This is a problem: the fattest sardines migrate farthest north, so the shrinking fish could help explain Canada's shortage. Smaller fish also reproduce less.
Flaky fish
Despite all this, Canada has continued to up their quotas.
These natural boom and bust cycles make all sardine fisheries fundamentally unsustainable, says Alec MacCall of the National Oceanic and Atmospheric Administration (NOAA) in La Jolla, California. "There can be periods of decades when no fishing should be allowed since reproduction cannot even replace the parental stock."
Fishermen need to earn a living, however, making it almost impossible to simply turn off a fishery. Instead, the US limits catches to just 15 per cent of the stock, and tries to match the boom and bust by cutting quotas when waters cool.
But although this is better than Canada's approach, Zwolinski fears the US has not cut quotas enough, as managers do not take account of other factors like the breeding condition of adult fish. As a result, even the US's small catches may be too large.
NOAA is holding an urgent meeting this week to review the US 2014 sardine quota.
Journal reference: PNAS, DOI: 10.1073/pnas.1113806109
If you would like to reuse any content from New Scientist, either in print or online, please contact the syndication department first for permission. New Scientist does not own rights to photos, but there are a variety of licensing options available for use of articles and graphics we own the copyright to.
Have your say
Only subscribers may leave comments on this article. Please log in.
Only personal subscribers may leave comments on this article
All comments should respect the New Scientist House Rules. If you think a particular comment breaks these rules then please use the "Report" link in that comment to report it to us.
If you are having a technical problem posting a comment, please contact technical support.
