TITLE: GLOBEC GROWTH AND CONDITION OF JUVENILE SALMON IN THE NORTHERN CALIFORNIA CURRENT
E. Casillas [Northwest Fisheries Science Center], J. Fisher [Oregon State University], K.C. Jacobson [Northwest Fisheries Science Center], G. H. Rau [University of California, Santa Cruz]
Salmon populations in the California Current, and coho salmon in particular, have been in severe decline since the 80s, coinciding with the 1977 regime shift, and contrasting to record productivity in the Gulf of Alaska. The specific linkages between oceanographic changes and salmon survival in the marine environment are not well understood. GLOBEC has chosen to compare two regions of the Northern California Current divided by Cape Blanco, Oregon (43 oN) where an "upwelling jet" moves off the shelf. The regions north and south of Cape Blanco differ in intensity and stability of upwelling, temperature, and offshore transport. Evidence indicates that due to the physical conditions, the distribution, and production of biota, may differ north and south of Cape Blanco providing the opportunity to compare and contrast the relationship between specific oceanographic processes and biological productivity. Through process oriented studies, we propose to examine mechanistic linkages between the physical and biological processes that are associated with habitat quality critical to recruitment of juvenile salmon. Juvenile coho (Oncorhynchus kisutch) and chinook (Oncorhynchus tshawytscha) salmon will be collected along transects between Eureka, CA to Newport, OR during May and September of 2000 and 2002. Sampling efforts will coincide with mesoscale and fine-scale surveys of physical (e.g., location of eddies, fronts, upwelling, offshore transport import; mixed layer depth, sea surface temperature, mixed layer depth) and biological (areas and density of primary, secondary productivity) features within the same regions conducted by other GLOBEC researchers. We will measure the growth rate, size variability, bioenergetic condition, pathogen prevalence and intensity in juvenile salmon as conditions of survival. By correlating our indices of condition with the measured biophysical characteristics of the different regions of the Northern CCS, and proposed trophic relationship studies, we will test the hypotheses that oceanographic features leading to high productivity of lower trophic levels translates to higher growth rates, condition and greater salmon recruitment through "bottom-up" forces. Also, the degree of correlation between these indices and variations in isotope natural abundances (14C,13C,15N) in juvenile salmon will be used to directly test the hypothesis that diet specificity and vertical ocean advection affect juvenile salmon health and condition. We will also compare juvenile coho and chinook salmon growth and condition from different regions of the Northeast Pacific (e.g. Alaska, British Columbia, Washington and northern Oregon) and to the historical record (prior to the last regime shift) where available and applicable. Our results will provide information on the relationships between ocean variability and juvenile salmon survival on temporal (interdecadal) and spatial (basin-wide, mesoscale, and local) scales.
In May and September of 2000, juvenile coho (Oncorhynchus kisutch) and stream-and ocean type chinook (Oncorhynchus tshawytscha) salmon will be obtained in collaboration with a sampling program proposed by Brodeur et al. (see Table 1). They will collect juvenile chinook and coho salmon along transects in the California Current from Eureka, CA to Newport, OR and on finer-scale intensive sampling focussed around areas of contrasting physical structures. We will be involved in cruise preparation and sampling efforts. Following cruises, we will obtain length and weight characteristics (variation in mean size, condition index, and allometric relationships), of salmon for correlation with physical oceanographic features (e.g. eddies, coastal fronts, upwelling) and zooplankton biomass north and south of Cape Blanco, OR. We will dissect salmon to obtain tissues for bioenergetics and pathogen analysis (for our study) and other GLOBEC collaborations including: Brodeur and Wainwright ("GLOBEC Trophic Relationships of Juvenile Salmon in Coastal Waters off Oregon and California: Top-down or Bottom-up Control"), and Grant et al. (genetic stock composition of the juvenile salmon sampled from the different regions in the California Current.) Scales and otoliths will be taken for measurements of growth rates and identification of ocean and stream-type chinook salmon. We will sample liver and muscle tissue for bioenergetic assessment, and blood, kidney and muscle to assess levels of selected bacterial, viral and parasitic pathogens. Muscle 13C 15N and 14C natural abundance will also be measured. Differences in growth and condition indices will be used to assess the overall quality of the different coastal zones and to determine if and which oceanographic features contribute to salmon productivity. Correlations (or lack there of) between the preceding fish health/condition measures and fish: a) 13C and 15N, and b) 14C variations will be used to assess the respective effects of diet specificity and vertical ocean advection on fish health/condition. All data obtained on individual fish will be entered into a single database available to all collaborators. We will initiate comparisons of growth, condition indices and isotope abundances in juvenile salmon sampled north and south of Cape Blanco, OR (this study), as well as with juveniles sampled concurrently in and around the Columbia River plume (Schiewe et al., NWFSC, NMFS; BPA # 9603), off the coast of British Columbia (Welch et al., Fish and Oceans, Canada) and off of southeast Alaska (Orsi et al., AFSC, NMFS).
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Oregon State University
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