Later On

A blog written for those whose interests more or less match mine.

The loss of forage fish

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A somewhat disheartening article by Ellen Pikitch in The Scientist:

Despite their vital role in maintaining healthy oceans and their high economic value, only in recent years have forage fish—small fish that rank relatively low in the ocean’s food chain, such as sardines, anchovies, and herring—finally begun to garner the attention they deserve. Forage fish account for more than one-third of the world’s marine fish production, but are rarely directly consumed by people. Ninety percent of the catch is used in agriculture, in aquaculture, and as health supplements in the form of fish oil, which is valued for its rich supply of healthful omega-3 fatty acids.

To meet the demand of the industries depending on them, these fish are being pulled from the ocean at an enormous and increasing rate, resulting in serious declines in their numbers and knock-on effects that reverberate through ocean ecosystems. With price and demand continuing to skyrocket, it’s time to hit the brakes, and implement smarter management policies to avert further damage.

The recently released report, “Little Fish, Big Impact,” authored by the Lenfest Forage Fish Task Force, an international team of 13 preeminent marine and fisheries scientists, sheds new light on the ecological and economical importance of forage fish. The authors, including myself, found that more than half the diet of many seabirds, marine mammals, and larger fish, such as tuna, cod, and salmon, consists of forage fish. And, as their food supply has declined, so has the abundance of these predator species. The report also revealed that the value of forage fish left in the ocean to support production of larger, commercially important species is twice their value in a net. Overall, forage fish are worth nearly $17 billion per year to commercial fisheries—$5.6 billion as direct catch and $11.3 billion as food for larger commercially important fish.

Prior to the formation of the task force, management guidance for forage fish generally focused only on forage species and ignored the many other species that depend upon them. Indeed, high fishing rates in the past led to boom-and-bust fishery yields and some spectacular collapses. In the Barents Sea, repeated collapses of the forage fish capelin in the 1980s and 1990s caused nutritional stress and cannibalism in cod, a predator fish, with consequent economic losses to the cod fishery. Starving mammals and sea birds died or left the area. This situation was addressed by the Joint Norwegian-Russian Fishery Commission establishing what is called the “capelin rule,” which prohibits fishing of capelin if the biomass of the population falls below 200,000 tonnes. This rule has been successful in preventing further collapses of capelin, and has also restored the cod population in the Barents Sea to very high levels.

After 3 years of intensive work involving the synthesis of existing information and the development of new science, including a global analysis of 72 food web models (Fish and Fisheries, DOI:10.1111/faf.12004, 2012), the task force came to our conclusion: . . .

Continue reading.

Written by LeisureGuy

6 November 2012 at 12:38 pm

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