Pacific cod (open mouth shown above) are big eaters, and so are Steller sea lions. To understand food requirements of commercially important fish —and ensure enough are left in the water to sustain predator species—managers use multiple tools and mountains of painstakingly collected data. NOAA’s predator-prey database for Alaska groundfish exceeds 1 million records. Longstanding ”ecosystem caps” constrain the total of all catch limits below stock maximum sustainable removal levels calculated for fish stocks. Meanwhile intensive research and a battery of conservation measures seek to ensure fishing does not deplete food supplies for other species.
In 1998 the North Pacific Council acted to prevent development of new unrestricted fisheries for forage fish, protecting food sources for marine mammals, seabirds, and commercially harvested fish. A leading champion for the measure was Chris Blackburn, then director of the Alaska Groundfish Data Bank in Kodiak. “Prohibiting the commercial use of forage fish at this time is a pro-active move of which the [North Pacific Fishery Management] Council can be proud,” she wrote in a comment letter to the Council (April 9, 1997). “Harvesting both predators and prey is akin to burning a candle at both ends.”
In the North Pacific, “forage fish” is defined to include over fifty species. Among them are krill, smelt, capelin, eulachon, sand lances, sandfish, pricklebacks, gunnels, lanternfish, blacksmelts, and bristlemouths.On these species:
Based on available science, managers have acted to ensure that fishing does not compete for prey with the endangered western stock of Steller sea lions. A network of protection areas currently protect more than 100,000 km2 of feeding habitat for the mammals. These areas bar specific fisheries (chiefly Atka mackerel, cod, and pollock) from feeding grounds, especially at times when sea lions need abundant prey.
For example, Steller sea lions ordinarily eat 6-10% of their weight each day, but nursing mothers may consume three times more fish to feed their young. The closures combine with additional regulations that disperse harvests (both spatially and temporally) to restrain concentrated removals in sea lion habitat, leaving fish in the water where sea lions need it most. Download map as PDF, here.
Among the eight regional councils that govern fisheries in the US EEZ, the North Pacific Council was the first to develop a Fishery Ecosystem Plan (FEP). The 2007 Aleutian Islands FEP guides both research and management efforts to keep fisheries safely within ecosystem limits, understand foodweb interactions, and implement Ecosystem Based Fishery Management. In December 2015, the Council decided to prepare an FEP for the Bering Sea. Consideration of whole ecosystems has taken root throughout the North Pacific. One example: instead of relying solely on single-species stock assessments to set catch limits, managers now have access to detailed ecosystem indicators for each major ecoregion under the Council’s management.