Apr 4 2017

Hilborn-led study: Predators less affected by catch of prey fish than thought

Stocks of predatory fish may be less affected by the catching of their prey species than has previously been thought, according to new research published on April 3.

The study – published in journal Fisheries Research and led by well-known University of Washington professor Ray Hilborn – suggests previous studies on this topic overlooked key factors when recommending lower catches of “forage fish”.

Said forage fish include small pelagic species, such as anchovies, herring and menhaden.

The team of seven fisheries scientists found that predator populations are less dependent on specific forage fish species than assumed in previous studies, most prominently in a 2012 study commissioned by the Lenfest Ocean Program, which is managed by the Pew Charitable Trusts.

The Lenfest Forage Fish Task Force at that time argued that forage fish are twice as valuable when left in the water to be eaten by predators, and recommended slashing forage fish catch rates by up to 80%.

For fisheries management, such a precautionary approach would have a large impact on the productivity of forage fisheries. As groups such as IFFO (the Marine Ingredients Organisation) have noted, these stocks contribute strongly to global food security, as well as local and regional social and economic sustainability.

The new research claims to have found multiple omissions in the methodology of the Lenfest study.

“When you review the actual models that were used [by Lenfest], there are a few key elements on the biology of these animals that were not represented,” said Ricardo Amoroso, one of the study’s co-authors. He added that one of the authors’ approaches was to “look for empirical evidence of what is actually happening in the field.”

Previous studies relied on models which took for granted that there should be a strong link between predators and prey.

Specifically, the Lenfest study and another study using ecosystem models ignored the natural variability of forage fish, which often fluctuate greatly in abundance from year to year, this new study said.

It also failed to account for the fact that predators tend to eat smaller forage fish that are largely untouched by fishermen.


These failings were acknowledged by a co-author of that study, Carl Waters, who is also one of the co-authors of the new paper.

Because of these oversights, the new study concluded that the Lenfest recommendations were overly broad, and that fisheries managers should consider forage species on a case-by-case basis to ensure sound management.

“It is vital that we manage our fisheries to balance the needs of the ecosystem, human nutrition and coastal communities,” said Andrew Mallison, IFFO director general. “These findings give fishery managers guidance based on science, and update some of the inaccurate conclusions of previous reports.”

Two further authors of the Lenfest study – Tim Essington and Éva Plagányi – also went on to publish a paper in the ICES Journal of Marine Science, noting previous analyses used insufficient models.

They found that the distribution of forage fish has a greater impact on predators than simply the raw abundance of forage fish, as well as noting the importance of forage fish as a part of human food supply chains, praising their high nutritional value, both through direct human consumption and as food in aquaculture, as well as the low environmental impact of forage fishing.

“Cutting forage fishing, as recommended by the Lenfest group, would force people to look elsewhere for the healthy protein and micronutrients provided by forage fish – likely at much greater environmental cost,” the authors wrote.

“Forage fish provide some of the lowest environmental cost food in the world – low carbon footprint, no water use,” said Hilborn.

“[There are] lots of reasons that forage fish are a really environmentally friendly form of food.”

You can read the newly-published study in full here.

Only in February 2017 the NGO Bloom Association issued a report — “The Dark Side of Aquaculture” — claiming industrial fisheries reduce edible wild fish into fishmeal, when they are perfectly edible by humans.

Read the original post here: https://www.undercurrentnews.com/

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