Fisheries management moves toward broader, ecosystem-based approach

Nature : Because of global warming, fisheries managers may be forced to change the way they determine yearly catch limits and take a broader approach that includes a better understanding of ecological processes. Traditionally, managers set catch limits based on the populations of individual species and assumptions about population trends. However, an unusually warm water mass in the northern Pacific Ocean over the past 18 months has prevented forage species such as anchovies, sardines, and krill from migrating to coastal waters, where they are a major food source for salmon, tuna, and whales. Moreover, those forage species are already at historic low numbers, and a possible El Niño later this year could further disrupt the food chain. New tools, such as the California Current Predator Diet Database, are providing a more comprehensive, ecosystem-based approach through consideration of such variables as predator–prey relationships, climate, and economic factors.