When the SURFs up, forage fish are key

A novel method for identifying “key” prey species such as forage fish, upon which upper trophic level predators depend, is proposed. Forage fish fisheries collectively constitute 30% of global fishery landings and are important prey for other fished species as well as marine mammals and seabirds. The SURF index (SUpportive Role to Fishery ecosystems) for each prey species weights food web connectance by the importance of trophic connections, so that higher scores indicate a greater potential for indirect food web effects of forage fish fisheries. We show that the SURF index is less sensitive to choices on degree of taxonomic aggregation of analysis than typical connectance measures. Moreover, we show that SURF provides more robust predictions of which species have greatest effects on other food web components. This rapid and empirically based method has utility in ensuring that management plans for these species take into account the broader ecosystem impacts of different harvest levels.