Unusually warm ocean strengthens calls to consider ecosystem variables in setting catch limits.
Unprecedented conditions in the Pacific Ocean have sent fisheries managers into uncharted waters. ‘The blob’, an unusually warm water mass that has been parked in the northern Pacific for 18 months, has quelled upwelling that typically delivers nutrients to coastal waters where migratory salmon, tuna and whales fatten themselves on ‘forage species’ such as anchovies, sardines and krill.
The nutrient shortage comes at a time when many of those forage species are already at historic lows. With a strengthening El Niño — warmth in the eastern equatorial Pacific that affects weather patterns worldwide — fisheries managers face a good deal more uncertainty than usual as they prepare to set catch limits for next year.
The situation lays bare the urgent need to improve how ecological processes are taken into account in fisheries decision-making, scientists said at the American Fisheries Society annual meeting in Portland, Oregon, this week. Managers tend to base catch limits on fish-stock assessments that focus on individual species and presume that population trends are stable. Ecosystem-based fisheries management aims for a more comprehensive, long-term approach that considers variables such as predator–prey relationships, climate conditions and economic factors.
“This year is an excellent case study showing that we need to do ecosystem-based fisheries management,” said Jason Link, senior scientist for ecological research with the US National Oceanic and Atmospheric Administration (NOAA) in Woods Hole, Massachusetts.
Up to now, the bodies that set fisheries catch limits have only sparingly used ecosystem-based approaches. But last November, the Pacific Fishery Management Council, which makes catch recommendations for the West Coast to the US National Marine Fisheries Service, reviewed and conditionally endorsed a comprehensive ecosystem-based computer model — the first step towards bringing such a tool into management decision-making. Isaac Kaplan, a research fisheries biologist at NOAA’s Northwest Fisheries Science Center in Seattle, Washington, who led the model's development, says that it will next be used to predict how the northern Pacific ecosystem will respond to looming challenges such as depleted sardine populations and ocean acidification caused by global warming.
Ecosystem-based fisheries management is a hardly a new idea. “There have been countless calls for fisheries management to adopt a broader approach, but uptake of these principles has been relatively slow,” said Tim Essington, a fisheries scientist at the University of Washington in Seattle.
The biggest barrier may be the need to collect and analyse the relevant biological data, such as information on predator–prey relationships. “We realize that, to get buy-in, we need to offer busy managers efficient ways to simplify their work and avoid problems,” Essington said. He is co-chair of a task force that is looking into how to implement ecosystem-based fisheries management; it aims to publish a blueprint next year.
To help with planning, supporters of ecosystem-based fisheries are creating tools such as the California Current Predator Diet Database, which is amassing information about the eating habits of 119 Pacific species. Such information is valuable for predicting how fluctuations in the population of a prey species will affect its predators. At the fisheries meeting, Amber Szoboszlai, a research analyst at the Farallon Institute for Advanced Ecosystem Research in Petaluma, California, showed how she had used the database to find that fish eat 75% of the anchovies consumed in the Pacific, whereas mammals eat only 16% and seabirds 7%.
Also at the meeting, Link presented a plan that will have the National Marine Fisheries Service implementing ecosystem-level tools within 3–5 years to assess the risk of overfishing and the vulnerability of the fishery to climate change. Meanwhile, the conservation community is concerned about the potential for a wide-scale fisheries collapse in the face of the blob and El Niño. If, as some fear, the blob signals a regime change in how the Pacific behaves, they argue that ecosystem-based management will be essential to preventing such a catastrophe. “The whole system seems to be changing radically,” says Rebecca Goldburg, director of ocean science for the Pew Charitable Trusts in Washington DC, “making the case for ecosystem-based management more urgent.”
Related links in Nature Research
Related external links
About this article
Cite this article
Gewin, V. North Pacific ‘blob’ stirs up fisheries management. Nature 524, 396 (2015). https://doi.org/10.1038/nature.2015.18218