Task Force members Philippe Cury and Ian Boyd are coauthors on a paper in Science showing impacts to seabirds when forage fish are depleted below one-third of their maximum level."

A Call to Protect Humble Fish, for Seabirds’ Sake
New York Times
December 22, 2011

By Cornelia Dean

When people talk about the environmental effects of salmon aquaculture, they usually focus on water pollution and the spread of disease to wild fish stocks. But there is another big problem: It takes more than a pound of fish to produce a pound of salmon.

Farmed salmon are usually fed pellets made from ground-up fish like herring. Salmon farms have a prodigious appetite for this food, which has increased fishing pressure on creatures like herring, anchovies, krill and other “forage fish” at the bottom of the food web. Demand for fish oil and fish for the table is also a factor.

Now researchers from around the world are suggesting this pressure must be limited. Their motto is “a third for the birds.”

In other words, they write in Friday’s issue of the journal Science, fisheries managers should make sure that forage fish stocks do not fall below one-third of their historic maximum long-term biomass — the total amount of the fish, by weight.

When stocks fall below that level, the researchers write, breeding rates start to falter for seabirds and possibly for predatory fish and marine mammals as well.

The scientists, from North America, Europe and Africa, say that other studies have linked forage fish abundance to seabird breeding success, but they say their analysis is the first to suggest that one-third of maximum historical abundance is a critical boundary.

The scientists, led by Philippe M. Cury of the Mediterranean and Tropical Halieutic Research Center in Sète, France, studied gulls, kittiwakes, terns, puffins, penguins and other species, in waters off Alaska, New Zealand, Europe, western North America and elsewhere. They said their analysis of data, collected “over multiple decades,” shows that the one-third figure seems to apply regardless of “life history strategies, habitat preferences and population sizes of the seabird species considered.”

They concede that factors like habitat changes, predation on seabirds, interactions among bird species and the birds’ ability to switch to different prey may also play a role. Also, little is known about historic abundance levels of some fish species, making it difficult to define their maximum abundance.

But for most economically important species, “sufficient data to define the threshold” are available, they write.

Read the article in the NY Times.

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