Life Histories and Distributions of Copper River Fishes (.pdf)

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stocks of chum stay out for 3-4 years, while chum on the southern end of the range usually stayout for 2-3 years (Watson, 1999). Pink salmon may be major competitors for food while at sea.Chum salmon have strong homing abilities and usually return to their natal streams. Spawningtimes for northern stocks are usually earlier than southern stocks. Distinct summer and autumnruns or autumn and winter runs are often present in the same streams (Fig. 10).Figure 10. Chum engaging in spawning behavior (Watson, 1999).For chum salmon native to the southeastern Alaska, the peak of the nearshore abundancewas established, for 1984, as the first two weeks of in August (Clark and Weller, 1986). In theCopper River-Prince William Sound area, chums are available to fishermen during July andAugust.Sockeye SalmonThe sockeye or red salmon, Oncorhynchus nerka, exhibits the most diverse life cycle ofall of the Pacific salmon species. These salmon usually weigh between 4 and 8 pounds as adults.Spawning usually takes place in streams that flow directly into lakes, but also may occur in theoutlets of lakes, and in lakes themselves. In different areas of the Sitkine River drainage, innorthern British Colombia, sockeye have adopted all three different life strategies; some riverspawnedyoung head straight to sea after emerging, others spend almost a year in the river, whilethose with access to a lake use that as their nursery (Watson, 1999). It is estimated that in theCopper river of Alaska about 20% of the run spawns in the Delta (Morrow, 1980). Sockeyeusually spawn in the inflows of what are to be the nursery lake for their young, which drift downon the current into the lake immediately after they emerge (Watson, 1999). This dependence onlarge lakes along rivers systems constrains the sockeye salmon range to northern latitudes, wheresuch habitat is more common.Page 12 of 27
After spending one winter in the gravel, eggs hatch, and the fry migrate to the lakes,where they will spend at least another winter (Fig. 11). Typically, but not universally, juvenileanadromous sockeye utilize lake rearing areas for one to three years after emergence from thegravel; however, some of the population utilize stream areas for rearing and may migrate to seasoon after emergence (Groot and Margolis, 1991). Emergence occurs mainly at night, with peakout migrations during the darkest part of the night. Fry emergence usually coincides with thepeak in plankton blooms in downstream natal lakes in which they will rear. Here, they will growquickly to prepare for smoltification and migration to the ocean.Figure 11. Sockeye smolts (Watson, 1999).In spring, smoltification is triggered, and sockeye migrate in schools out of their natal lakeswithin days of ice-breakup. Some sockeye never leave the lakes, and complete their whole lifecycle in freshwater. These so called “kokanee” are usually reproductively isolated from sockeyeby differences in spawning timing and areas.Sockeye spend one to four years in the ocean before returning in late summer and autumn(Fig. 12). Sockeye salmon are distributed throughout the North Pacific Ocean, the Bering Seaand over to the eastern Sea of Okhotsk. During the winter, there is a general shift of distributionssouthward. Stocks then shift again northward with the approach of spring and the warming ofocean surface waters. Adaptations to lake environments seem to require better homing skills tolocate such restricted spawning areas. The adult sockeye return to their natal streams during thesummer and fall – from July to October in most areas – but as late as December in the southernpart of their range (Morrow, 1980).In Alaska, the largest harvest of sockeye salmon occurs in Bristol Bay, with other largeharvests coming from Cook Inlet and Prince William Sound. Around Cordova, sockeye salmonare the first salmon to return. Good numbers of adults begin to return to Eyak River in late MayPage 13 of 27
Page 1 and 2: Life Histories and Distributions of
Page 4 and 5: spawning areas in this region are t
Page 6 and 7: Figure 4. Chum salmon fry (Groot an
Page 8 and 9: summer, and others, as in the Karlu
Page 10 and 11: sometimes specialize on certain pre
Page 14 and 15: and early June. Alaganik Slough and
Page 16 and 17: depending more on body size than ag
Page 18 and 19: stocks of this species in North Ame
Page 20 and 21: that 10 and 12 years old. The retur
Page 22 and 23: with several bony plates, giving th
Page 24 and 25: tributaries in the upper watershed
Page 26 and 27: Fleming, D. F. 1999. Surveys and st

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