D.B. Pleschner: Study: No correlation between forage fish, predator populations

On April 9-10, the Pacific Fishery Management Council is meeting in Sacramento to deliberate on anchovy management and decide on 2017 harvest limits for sardine, two prominent west coast forage fish.

Extreme environmental groups like Oceana and Pew have plastered social media with allegations that the anchovy population has crashed, sardines are being overfished and fisheries should be curtailed, despite ample evidence to the contrary.

Beyond multiple lines of recent evidence that both sardines and anchovy populations are increasing in the ocean, a new study published this week in the journal Fisheries Research finds that the abundance of these and other forage fish species is driven primarily by environmental cycles with little impact from fishing, and well-managed fisheries have a negligible impact on predators — such as larger fish, sea lions and seabirds.

This finding flies directly in the face of previous assumptions prominent in a 2012 study commissioned by the Lenfest Ocean Program, funded by the Pew Charitable Trusts, heirs of Sun Oil Company. The Lenfest study concluded that forage fish are twice as valuable when left in the water to be eaten by predators and recommended slashing forage fishery catch rates by 50 to 80 percent.

However, in the new study, a team of seven internationally respected fisheries scientists, led by Prof. Ray Hilborn, Ph.D., of the University of Washington, discovered no correlation between predator populations and forage fish abundance. The new research also found multiple omissions in the methodology of the Lenfest study. For instance, it — and other previous studies — used ecosystem models that ignored the natural variability of forage fish, which often fluctuate greatly in abundance from year-to-year.

Ironically, the Lenfest findings were largely based on a model called EcoSim, developed by Dr. Carl J. Walters, one of the seven co-authors of the new paper. Dr. Walters found that the EcoSim models used in earlier studies had omitted important factors, including natural variability, recruitment limitations and efficient foraging of predators.

The Lenfest study also failed to account for the fact that predators typically eat smaller sized forage fish that are not targeted by fishermen. In light of these omissions, the Hilborn et al study concluded that Lenfest recommendations were overly broad and should not be considered for fishery management. “The Lenfest conclusion … is not based on any fact,” said Dr. Carl Walters, “…it’s based on model predictions…models that we know now are fundamentally flawed. In hindsight, it’s an irresponsible recommendation.”

This isn’t the first-time ecosystem models used in earlier studies have been questioned. One year after the Lenfest study was completed, two of its authors, Dr. Tim Essington and Dr. Éva Plagányi, published a paper in the ICES Journal of Marine Science saying, “We find that the depth and breadth with which predator species are represented are commonly insufficient for evaluating sensitivities of predator populations to forage fish depletion.” The Hilborn et al study reaffirmed this finding, noting “several reasons to concur with the conclusion that the models used in previous analysis were insufficient.”

The authors concluded their study by noting the importance of forage fish as a part of human food supply chains, as well as the low environmental impact of forage fisheries. They also praised the high nutritional value of forage fish, both through direct human consumption and as food in aquaculture. Curtailing forage fisheries, as recommended by Lenfest, would force people to look elsewhere for the healthy protein and micronutrients provided by forage fish — likely at much greater environmental cost.

We all know it’s important to balance the needs of the ecosystem, human nutrition and coastal communities in the management of our fisheries. That’s why the Council should heed these new findings, and base management guidance on the latest, best scientific evidence. The future of California’s historic wetfish industry, the foundation of California’s fishing economy, hangs in the balance.

D.B. Pleschner is executive director of the California Wetfish Producers Association, a nonprofit dedicated to research and to promote sustainable Wetfish resources. More info at www.californiawetfish.org.

Original post on: http://www.santacruzsentinel.com/

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/