GLOBEC 2000: Relationship of growth and survival of coho salmon utilizing the coastal Gulf of Alaska
W.R. Heard, J. Taylor, J. Orsi (all at NMFS/AFSC, Auke Bay Laboratory), and M. Adkison (Juneau Center of Fisheries and Ocean Sciences, University of Alaska, Fairbanks)

The U.S. GLOBEC effort in the Northeast Pacific is directed at an overall goal of improving predictability of living marine resources of the region through improved understanding of ecosystem interaction and the coupling between the physical environment and the living resources. Salmon (Oncorhynchus spp.) are keystone species for the research effort because of their economic and ecological importance and because of the linkage of regional abundance of salmon stocks to climatic shifts in the North Pacific. Salmon from different regions of the North Pacific have responded differently to the recent warming that has occurred in the North Pacific. For example, coho salmon in the Pacific Northwest have declined precipitously, precipitating wide-spread listings of coho salmon populations in that region under the Endangered Species Act. In contrast, coho salmon catch from populations adjacent to the Gulf of Alaska have been at historically high levels in the 1990's. The major hypotheses of the North Pacific Climate Changes and Carrying Capacity Science Plan are that: (1) Ocean survival of Pacific salmon is determined primarily by survival of juvenile salmon in coastal regions, and is affected by interannual and interdecadal changes in Gulf of Alaska physical forcing; and (2) Variation in size-at-age of returning salmon is determined largely by interdecadal and interannual variation in physical conditions and productivity of the oceanic realm of the subarctic Pacific, and may show density dependence. This project will use retrospective analyses of archived coho salmon scales from an Alaska stock and on-going marine collections of juvenile coho salmon to directly address these hypotheses, and to develop a forecasting model for year-class strength of coho salmon returning to Southeast Alaska.

The retrospective analysis will be of archived scales collected from juvenile and adult coho by two long-term monitoring programs supported by the NOAA Auke Bay Laboratory. At Auke Creek, coho salmon scales have been collected from adults returning to Auke Creek from 1971-1999. All coho salmon smolts leaving Auke Creek since have been coded-wire tagged since 1976, all returning adults have been examined for tags, and Alaska Department of Fish and Game samples the commercial and sport fisheries to estimate harvest, so accurate and precise marine survival data have been compiled for this stock. Scales will be digitized, and marine growth will be broken into three phases: juvenile nearshore/coastal; juvenile Gulf of Alaska; and adult. These growth data will be analyzed for correlation with size at return, stock-specific marine survival, abundance of coho in Southeast Alaska fisheries, and measured biophysical characteristics of the Gulf of Alaska environment, including air and sea surface temperature records and climatic indices such as the Aleutian low pressure index. These data will be used to create a hindcast model relating phase-specific growth and environmental variates to survival and year-class strength.

Scales from juvenile coho salmon captured in the marine environment by the Auke Bay Laboratory's Southeast Alaska Coastal Monitoring (SECM) program will also be digitized and analyzed. Scales are available from archived samples since 1997, and sampling will continue through 2005. These scales will provide information to estimate circuli growth at the time of migration from inside waters into the coastal gyre and the Gulf of Alaska. Scale growth data from the juvenile collections will be used to test the hindcast model for forecasting accuracy, and size, condition, and relative abundance data from the SECM will be evaluated as auxiliary variables for explaining interannual variation in year-class strength and stock-specific marine survival.

This page was last updated on October 2, 2000.

Maintained by:
Hal Batchelder [hbatchelder@coas.oregonstate.edu
College of Oceanic & Atmospheric Sciences
Oregon State University
Corvallis, OR 97331-5503
phone: 541-737-4500; FAX 541-737-2064