Forage fishes are key energy conduits that transfer primary and secondary productivity to higher trophic levels. As novel environmental conditions caused by climate change alter ecosystems and predator-prey dynamics, there is a critical need to understand how forage fish control bottom-up forcing of food web dynamics. In the northeast Pacific, northern anchovy (Engraulis mordax) is an important forage species with high interannual variability in population size that subsequently impacts the foraging and reproductive ecology of marine predators. Anchovy habitat suitability from a species distribution model was assessed as an indicator of the diet, distribution, and reproduction of four predator species. Across 22 years (1998–2019), this anchovy ecosystem indicator (AEI) was significantly positively correlated with diet composition of all species and the distribution of Common murres (Uria aalge), Brandt’s cormorants (Phalacrocorax penicillatus), and California sea lions (Zalophus californianus), but not rhinoceros auklets (Cerorhinca monocerata). The capacity for the AEI to explain variability in predator reproduction varied by species but was strongest with cormorants and sea lions. The AEI demonstrates the utility of forage species distribution models in creating ecosystem indicators to guide ecosystem-based management.

This data set is derived from a species distribution model developed by Barb Muhling (B. A. Muhling, et al., Predictability of Species Distributions Deteriorates Under Novel Environmental Conditions in the California Current System. Front. Mar. Sci. 7, 1–22 (2020)). We restricted the ranges of this SDM to the foraging range of three seabirds that breed in the Gulf of the Farallones off central California, and to the range of California sea lion foraging from a rookery at San Miguel Island in the Channel Islands. We took the average anchovy habitat suitability (probability of occurrence) during the reproductive season for each of these species to create our anchovy ecosystem indicator.

All analyses were performed in R.