GLOBEC: Physical Influences on California Current Salmon

University Of California-Davis, Davis CA

Investigators

Abstract

The GLOBEC NEP Program will continue annual long term observations (2D) in two parts of the California Current System (CCS), along with mesoscale (3D) and process studies in two field years. Through those studies the program aims to achieve a quantitative understanding of how physical and biological processes drive zooplankton and salmon populations, on time scales ranging from multi-decadal to weekly, and spatial scales from the basin to mesoscale. Modeling is required to integrate over the many disciplines involved, scales of variability, and levels of ecological organization, both as a part of the scientific process, and as a prospective tool to predict the effects of future climate change on these populations. As part of the GLOBEC Program the PIs will: (1) add a swimming capability to their bioenergetic model of individual CCS salmon and embed that in GLOBEC and CoOP physical models to explain salmon distribution, growth and survival in early ocean life, (2) describe implications for CCS salmon population dynamics of well known, but poorly understood effects of the ocean environment on salmon size structure, and (3) assess retrospectively relationships between CCS salmon spawner and recruit data and physical data from the CCS from multidecadal scales to the mesoscale. In addition the PIs will use numerical. experiments to test explanations of observed distributions, to see whether they meet bioenergetic and swimming speed constraints, and to evaluate their consequences regarding distributions of food and predators. Individual level analyses and existing data indicate environmental influences on growth affect not just survival, but also maturity schedules, an effect whose consequences for population and metapopulation dynamics and for retrospective are not known. GLOBEC NEP conclusions regarding the response of this ecosystem and salmon populations to climate change will require consistency with past data. The PIs will refine their retrospective results by relating decadal and annual scales to seasonal, mesoscale mechanisms, using recruitment and spawner data (which are less confounded than catch) and accounting for freshwater conditions. As GLOBEC NEP reaches completion 4 or 5 years from now, the modeling and retrospective studies will be integrated to provide a prospective summary.