GLOBEC: Physical Influences on California Current Salmon
Louis W. Botsford and Alan Hastings [University of California, Davis], John L. Largier [Scripps Institution of Oceanography]

Over the next several years GLOBEC NEP plans continuing 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. Here we propose: (1) to add a swimming capability to our 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) to describe implications for CCS salmon population dynamics of well known, but poorly understood effects of the ocean environment on salmon size structure, and (3) to assess retrospectively relationships between CCS salmon spawner and recruit data and physical data from the CCS from multidecadal scales to the mesoscale. In first half of our current 3-year GLOBEC NEP modeling grant, we: (1) have developed a bioenergetic model of individual CCS salmon and are using it as a common functional framework to assess relevant extant data regarding effects of size and time of ocean entry and ocean environment on early growth and survival, and consequent maturation and spawning, (2) have shown how the effect of the ocean environment on salmon populations depends on the age of environmental influence (early ocean vs. maturing), the age structure of the species (obligate semelparous coho vs. chinook), and the temporal scale of ocean variability (annual vs. multi-decadal), and (3) have shown through retrospective analysis that "warm ocean" conditions drive populations of both CCS salmon species and Dungeness crab. Assessment of NEP field data on salmon distribution relative to mesoscale circulation will require a model of individual salmon to test hypotheses regarding swimming behavior. We propose numerical experiments testing 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. Our 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. We will refine our 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, our modeling and retrospective studies will be integrated to provide a prospective summary.

This page was last updated on March 14, 2007.

Maintained by:
Hal Batchelder
College of Oceanic and Atmospheric Sciences
Oregon State University
Corvallis, OR 97331-5503
phone: 541-737-4500; FAX 541-737-2064