U.S. GLOBEC: Physical Influences on Populations in the California Current (Botsford, L. [Univ. Calif. Davis (UCD)], Hastings, A. M. [UCD], Largier, J. [Scripps Institute of Oceanography]) We propose to formulate models spanning the individual level to the metapopulation level for two genera of interest to GLOBEC in the CCS: ( 1) the two CCS salmon species identified by GLOBEC, coho salmon (Oncorhynchus kisutch) and chinook salmon (O. tshawytscha) and (2) Dungeness crab (Cancer magister), a species which covaries with salmon, is a significant prey of both species, and is subject to similar mesoscale circulation patterns. The ultimate purpose of these models will be to link the different scales of variability and levels of ecological organization in the various retrospective, monitoring and process studies so that the effects of changes in the physical environment on populations can be projected. Also, we will answer a number of questions through modeling and analysis of existing data, that will allow better focus of field studies on critical issues.

While upwelling and the regime shift in the mid-1970s are believed to have affected survival through this period, results of field studies of the cause are equivocal. We will develop a model to evaluate the interaction of time of ocean entry, size at entry, varying growth rate, and size dependent mortality rate on the fraction surviving this phase, and use it to compare the various field results in a common context. The results will help to focus field studies, and the model will provide a framework for evaluation of those studies. Even though Core Hypothesis III focuses on the juvenile stage, ENSO events are known to have a dramatic effect on survival of pre-spawning adults. Because the behavior of random populations of semelparous, anadromous species is poorly understood, the relative effects of environmental variability on their persistence and productivity is unknown. We will formulate a population model to determine which variable life history stage has the greater effect so that the GLOBEC process studies can focus on the appropriate one. We will formulate a metapopulation model to evaluate whether covariability between the environmental influences on different subpopulations affect persistence, and if it does, whether more productive populations can "rescue" extinct less productive populations?

We will also model and analyze the Dungeness crab population because the dramatic fluctuations in their abundance along the coast may be caused by the same environmental factor(s) that cause the salmon populations to vary, and may also be a cause of that variability through predation. We will apply a new approach to population analysis that answers the question: which environmental forcing function can combine with known density-dependent recruitment mechanisms to produce the observed variability in crab catch?

This page was last updated on March 15, 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