News Column

Overfishing: Ocean Food Chain In Danger

March 23, 2012

Craig Welch

tuna

As ocean scientists probe what ails some of the largest creatures in the sea, a wave of new research is urging them to look at the little things - specifically the tiny schooling fish that make up the cornerstone of ocean food webs.

Species like herring, smelt, sardines and squid are the food of choice for many of the ocean's top predators. But there is increasing pressure globally to harvest marine "forage fish" for everything from hog feed and fertilizer to fishmeal in tuna pens or as bait for recreational or commercial fishing.

And these creatures are often the fish scientists understand the least.

"The idea that forage fish are important isn't new," said Phil Levin, a biologist with the National Marine Fisheries Service in Seattle. "But if you take the fish out of the system ... what are the costs if those fish are no longer there to be eaten by birds or mammals or other fish? That's what we're talking about now."

Take, for example, the discovery late last year by an international team of scientists who tracked what happens to birds when the small fish they eat vanish.

Those researchers stumbled upon a remarkable pattern: Every time populations of ocean forage fish - small schooling creatures like squid or anchovies - dipped below a third of their peak, seabird births also plummeted, according to the study published in late December in the journal "Science." It happened with terns and gulls and auklets and puffins. It happened in the Atlantic, the Arctic, in Europe and off the U.S. West Coast.

Then, late last month, another pair of scientists determined that sardine populations from California to Washington appeared likely to collapse in coming years, just as they had during the "Cannery Row" days of the middle 20th century.

Other experts disputed the finding, but the debate highlighted an emerging conflict in marine science.

These tiny fish, while resilient, may be especially vulnerable to overfishing, climate change, habit loss and shifting ocean chemistry. And their loss could have profound impacts throughout marine ecosystems - far more so, even, then the loss of some well- known predators.

"In the big picture, there are growing concerns globally that some forage fish stocks are unhealthy and the way we harvest them is unsustainable," said Bill Sydeman, a marine biologist with California's Farallon Institute and member of the team that worked on the bird study.

There's no clear pattern off the coast of Washington and Oregon. Fisheries for anchovies and herring are relatively small, and researchers say that while sardine populations have been in decline, there has also been a recent rebound and fishing pressure remains a fraction of what it was a half-century ago.

But some other species - such as the tiny endangered oceangoing smelt called eulachon found in the Columbia River and its tributaries - are facing dramatic reductions from habitat loss, climate changes and other factors. And the big battle shaping up is what to do next - whether to study and protect the important tiny schooling creatures we don't really fish yet at all.

Some see potential future protein in the voluminous, glowing lanternfish that occupy deep waters in the Pacific, or the slender eel-like sand lances that feed larger fish. But others see the future stability of an ocean food chain already in flux.

"We know that predator species, marine mammals and seabirds are very dependent on forage species," said Paul Shively, with the Pew Environment program that is working to prevent expansion of commercial forage-fish harvests. "We know that the demand for forage species is growing. But most of our laws exist to promote fishing - not to make sure we're considering impacts on the entire ecosystem."



Source: (C) 2012 Charleston Gazette.