A predictive understanding of salmon abundance is still lacking despite GLOBEC NEP's program of field sampling, retrospective analysis and modeling, a strong comparative component and observation of an environmental shift in 1999/2000. Although the physical/biological conditions associated with (1) annual variability in fish survival, and (2) the spatial distribution of juveniles are amenable to description, neither the underlying mechanisms to explain them nor the link between two are known.
This proposal aims to achieve both understanding and predictability by using a comparative approach while synthesizing several data sets for coho salmon. This species was studied by GLOBEC in both Southeast Alaska (SEAK) and the California Current System (CCS), and its abundance covaries inversely in the two systems. The biological/physical conditions under which juvenile coho salmon were found in GLOBEC NEP-funded studies in SEAK and the variation of the juvenile salmon habitat over 8 years at one location and 4 years at another will be described. An individual-based model will be employed to assess the advantages of these habitats to growth and mortality of juvenile coho salmon, and to describe how individual salmon could interact with such spatial distributions. The findings of a GLOBEC-NEP funded retrospective study regarding potential predator buffering effects will be extended in time and space. Local indicators of biologically important physical conditions, based on local winds and general circulation, will be developed to study the response of individual stocks along the coast north of the bifurcation of the West Wind Drift (WWD). The coded wire tag data set, which spans both systems, will be used together with GLOBEC observations in the NEP to derive a model of coho salmon early life history that is consistent across the two systems, but can have different physical forcing in each.
The ultimate product of this project is an indicator of annual ocean conditions that affect salmon survival and age of spawning. This indicator will be directly useful in the short term in fishery management and in the long term by reducing the uncertainty and contentiousness surrounding management of factors influencing the freshwater phase of the salmon lifecycle. This project includes a graduate student and a postdoc.
