Cooperative artificial propagation programs for salmon and steelhead, 1995-1996

Fifteen cooperative fish rearing and planting programs for salmon and steelhead were active from July 1, 1995 through June 30, 1996. For all programs, 134,213 steelhead trout,(Oncorhynchus mykiss), 7,742,577 chinook salmon,(~ tshawytscha),and 25,075 coho salmon(~ kisutch) were planted. (PDF contains 26 pages.

Seasonal changes in growth of coho salmon (Oncorhynchus kisutch) off Oregon and Washington and concurrent changes in the spacing of scale circuli

In this study we present new information on seasonal variation in absolute growth rate in length of coho salmon (Oncorhynchus kisutch) in the ocean off Oregon and Washington, and relate these changes in growth rate to concurrent changes in the spacing of scale circuli. Average spacing of scale circuli and average rate of circulus formation were significantly and positively correlated with average growth rate among groups of juvenile and maturing coho salmon and thus could provide estimates of growth between age groups and seasons. Regression analyses indicated that the spacing of circuli was proportional to the scale growth rate raised to the 0.4−0.6 power. Seasonal changes in the spacing of scale circuli reflected seasonal changes in apparent growth rates of fish. Spacing of circuli at the scale margin was greatest during the spring and early summer, decreased during the summer, and was lowest in winter or early spring. Changes over time in length of fish caught during research cruises indicated that the average growth rate of juvenile coho salmon between June and September was about 1.3 mm/d and then decreased during the fall and winter to about 0.6 mm/d. Average growth rate of maturing fish was about 2 mm/d between May and June, then decreased to about 1 mm/d between June and September. Average apparent growth rates of groups of maturing coded-wire−tagged coho salmon caught in the ocean hook-and-line fisheries also decreased between June and September. Our results indicate that seasonal change in the spacing of scale circuli is a useful indicator of seasonal change in growth rate of coho salmon in the ocean

Feeding ecology of juvenile Pacific salmon (Oncorhynchus spp.) in a northeast Pacific fjord: diet, availability of zooplankton, selectivity for prey, and potential competition for prey resources

We investigated the feeding ecology of juvenile salmon during the critical early life-history stage of transition from shallow to deep marine waters by sampling two stations (190 m and 60 m deep) in a northeast Pacific fjord (Dabob Bay, WA) between May 1985 and October 1987. Four species of Pacific salmon—Oncorhynchus keta (chum) , O. tshawytscha (Chinook), O. gorbuscha (pink), and O. kisutch (coho)—were examined for stomach contents. Diets of these fishes varied temporally, spatially, and between species, but were dominated by insects, euphausiids, and decapod larvae. Zooplankton assemblages and dry weights differed between stations, and less so between years. Salmon often demonstrated strongly positive or negative selection for specific prey types: copepods were far more abundant in the zooplankton than in the diet, whereas Insecta, Araneae, Cephalapoda, Teleostei, and Ctenophora were more abundant in the diet than in the plankton. Overall diet overlap was highest for Chinook and coho salmon (mean=77.9%)—species that seldom were found together. Chum and Chinook salmon were found together the most frequently, but diet overlap was lower (38.8%) and zooplankton biomass was not correlated with their gut fullness (%body weight). Thus, despite occasional occurrences of significant diet overlap between salmon species, our results indicate that interspecific competition among juvenile salmon does not occur in Dabob Bay

Gravel galore: Impacts of clear-cut logging on salmon and their habitats

Timber harvest may have both direct and indirect effects on salmon, and with a few exceptions those effects result in lowered survival of salmon in their stream habitats compared with unlogged forest (Hicks et al. 1991b). Some impacts may be seen immediately or shortly after logging, whereas others can take decades to be expressed. Central to analyzing these effects is the context of the freshwater environment in which salmon are spawned and reared, and the life histories of the salmon species. This chapter will examine the effects of timber harvest on the freshwater habitat and life stages of salmon. It will also investigate the hypothesis that the salmon species least affected by timber harvest are those with the least reliance on stream habitats

Contribution of muskeg channel habitats to juvenile coho salmon production in the Situk River, Alaska

Thesis (M.S.) University of Alaska Fairbanks, 2006This study examines seasonal patters of habitat use by juvenile coho salmon in the Situk River and the importance of muskeg channels. To determine seasonal patterns I trapped fish from a range of habitats every two weeks during the summer of 2005. Analysis of the length-frequency data these samples provided showed most fry emerged in gravel bedded channels and that a substantial number of these fish then moved into muskeg channels during their first summer, rearing there until smolting at age 1 + or 2+. To estimate the number of coho salmon using muskeg channels, I established a relationship between channel width and fish density and scaled this up to the entire drainage using GIS analysis. This demonstrated that muskeg channels provide important rearing habitat. Comparison with published data suggests that muskegs are responsible for between 14% and 80% of total coho salmon smolt production in the Situk River