Predator Considerations: Approaches for Synthesizing Existing Forage Data and Applications to Fishery Management

Top predators often occur at a trophic level that competes with forage fisheries. Invertebrates and juveniles of large predatory fishes comprise much of the forage assemblage critical to predator population dynamics and fisheries services but are frequently overlooked because they don’t fit the traditional definition of “planktivorous coastal pelagics”.  Obstacles to EBFM include lack of synthesis of existing predator diet data and translation into formats relevant for management.  To better understand the importance of the array of forage, we assembled the California Current Predator Diet Database of published/technical literature on diet composition of over 120 marine birds, mammals and predatory fishes.  We examine predator dependency on forage and how this varies among taxa and spatio-temporally.  This process has indicated the need to develop a quantifiable, standardized approach to evaluating diet composition.  Examples show the importance of variance and misleading effects of averaging diet across spatio-temporal and ontogenetic differences.  Finally, we are using a multiple-model approach to synthesize not only how much forage the broad suite of predators consume California-Current-wide, but how much forage is needed in the water for successful predator growth/survival/reproduction - often much more than consumption due to the patchy nature and schooling behaviors of forage species.