Special Seminar Series: The Ecology of Monterey Bay
Process studies to quantify
ecosystem dynamics in the
central California Current
Brian K. Wells
Fisheries Ecology Division, Southwest Fisheries Science Center
National Marine Fisheries Service
National Oceanic and Atmospheric Administration
Tuesday, October 3, 2017
Pacific Forum—11:00 a.m.
I will describe the large- and regional-scale environmental conditions of the Pacific Ocean Basin and California Current shelf ecosystem that relate to forage, Chinook salmon, and seabird productivity in central California. This work expands on our understanding of ecosystem dynamics to benefit fisheries management. We argue that seasonality is a key element determining forage, Chinook salmon, and seabird productivities. The strength and location of the North Pacific High winds over the Pacific Ocean in winter influences shelf ecosystem productivity via winter upwelling and prey retention (krill and juvenile rockfishes) on shelf habitats prior to and during May and June when salmon out-migration to sea and seabird chick rearing occurs. The abundance of krill and rockfish prey on the shelf is positively correlated with juvenile salmon ocean survival and fledgling success of seabirds.
As a case study, the effects of ecosystem-level dynamics were related to salmon survival. We found in less productive conditions common murre seabirds occur in larger aggregations and forage more inshore, predominantly on adult northern anchovy. While foraging inshore, common murre consumption of juvenile Chinook salmon increases, which negatively impacts salmon population survival rate. Ultimately, we demonstrate through study of ecosystem interactions that the significance of top-down impacts on salmon (predation) are associated with bottom-up (upwelling) dynamics. This information can be used to refine ecosystem models and evaluate likely outcomes of ecosystem management options, including considerations of three fishery resources and recovering seabird populations.