Forage Species Swarm in Response to Coastal Upwelling

Abstract

We observed the distribution and identity of forage species to infer behavioral changes in response to intraseasonal variation in the coastal upwelling ecosystem of Monterey Bay, California. While the biomass of forage species remained comparable, the small-scale distribution of krill and anchovies was strongly affected by upwelling conditions. When regional upwelling influences were strong in the Bay, both species formed numerous discrete swarms and schools. During relaxation, both species were more diffusely distributed. Rather than gross changes in spatial distribution, a process that could take a long time for these relatively small animals, forage species responded to the short time scale dynamics that occur between days in the upwelling season with changes in their aggregative behavior. The behavioral responses observed highlight the need to study within-season dynamics in upwelling systems in addition to their cumulative influence in order to understand the ecological processes of these productive systems.