Physical-Chemical Structures, Primary Production and Distribution of Zooplankton and Planktivorous Fish on the Gulf of Alaska Shelf: A GLOBEC Monitoring Proposal. (Weingartner, T. J., Haldorson, L., Paul, A. J., Coyle, K. [all at Univ. of Alaska, Fairbanks], T. Royer [Old Dominion Univ.], T. E. Whitledge [Univ. Texas]) The Gulf of Alaska (GOA) shelf sustains a number of commercially significant fisheries. Despite dramatic changes in many of these fisheries in the late 1970s, little is known of the factors linking fish populations to the physical and climatic environment. Nevertheless. the existing oceanographic and fisheries data indicate variability on the same time scales as climatic changes. We propose to initiate a monitoring program, which in conjunction with GLOBEC process studies will aid in elucidating the links between the various physical, biological and climatic factors.

The basic water properties and circulation pattern of the GOA are coupled closely to the Aleutian Low pressure system; the atmospheric wind stress and precipitation drive a cyclonic, coastally downwelling system and produce the Alaska Stream and the narrow, freshwater Alaska Coastal Current over the shelf. Most of the zooplankton biomass on the GOA shelf in the spring and early summer is composed of oceanic species, thus implicating cross-shelf transport in the interannual variability in zooplankton densities. However, there is little data on primary production and nutrient concentration on the shelf, additional factors which could strongly influence zooplankton densities. Since zooplankton are critical to the growth and survival of planktivorous fish, factors impacting their abundance, distribution and species composition will ultimately impact populations of salmon, pollock and other commercially important stocks.

Specifically, we propose to document seasonal and interannual variability in the cross-shelf distribution of physical properties; the concentrations of nutrients, dissolved oxygen and chlorophyll; primary production rates; and the density and species composition of zooplankton. We will occupy a cross-shelf transect from the mouth of Resurrection Bay to the outer edge of the shelf break during each of six cruises per year, timed to coincide with key periods in the seasonal cycles of physical and biological events. Acoustic data will be used to document fish populations, and the species composition and condition of fish will be determined during the summer and fall cruises using samples collected by trawler. Sampling will be optimized during each cruise by real-time data analysis.

We also propose to identify the significant elements required for effective long-term monitoring beyond the time period of this study, to aid in the design of cost-efficient monitoring programs in the future. The effective duration of our data set will be greatly enhanced by existing data from previous hydrographic sections along our transect line, using a 26-year time series at one of the transect stations, and by a number of other oceanographic and climatic data sets. Retrospective studies using this enhanced data set, climatic records and a hydrological model will examine the historical relationship between the various physical and biological variables, thus aiding in the identification and validation of links between climate and the biological and physical environment.

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