Trade-offs between forage fisheries and predators

Forage fish generate economic benefits through directed fisheries, but also generate benefits through their role as prey to other valued species (large piscivorous fish, seabirds, and marine mammals). Previous evaluations of the ecosystem consequences of forage fish fisheries used models with coarse taxonomic resolution of forage fish and their predators, but here, trade-offs between forage fish fisheries and predator fisheries, and between forage fish fisheries and species of conservation interest in the California Current, were quantified using a taxonomically detailed foodweb model (populated by the CCPDD) and a generalized equilibrium model (Koehn et al. 2017). This new model predicted loss in catch of some higher trophic level fisheries (mainly salmon and California halibut) from fishing forage fish (sardine, anchovy, herring). Predicted reductions in biomass of seabirds and marine mammals were sufficiently large that, depending on the value of these non-market species, consideration of non-market predators could tip the balance of trade-offs toward conservation of forage fish and away from harvest. This work highlights specific predators (brown pelicans, marbled murrelets, multiple other seabirds, sea lions, baleen whales) that are potentially sensitive to specific forage fish fisheries in the California Current.