Apr 11 2017

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/

Leave a Reply