Habitat distributions of chinook and coho salmon underyearlings in the Big Qualicum River, Vancouver Island, B.C., under controlled flow conditions indicated that at similar sizes their habitat requirements during the first 3 months of stream life were similar. Just after emergence, fry of both species occupied marginal areas in association with bank cover. With increased size, the young fish moved into habitat of progressively higher velocity. However, differences between the species in time of emergence and size evidently resulted in a high degree of spatial segregation. Chinook fry emerged about a month earlier than coho, were larger upon emergence, and grew at a faster rate. Apparently, because of their larger size at a given time, chinook preferred higher velocity locations than coho.

Natural productivity, the number of natural-origin adult recruits per parent, is an important parameter for assessing population status of steelhead Oncorhynchus mykiss (anadromous Rainbow Trout) and Pacific salmon Oncorhynchus spp. listed under the U.S. Endangered Species Act. Hatchery-origin adults comprise a majority of many salmon and steelhead spawning populations. In such cases, the utility of natural productivity estimates is affected by uncertain reproductive fitness of hatchery spawners and by possible ecological or genetic interactions among hatchery and natural fish. This study examined options for analyzing population census data to assess hatchery spawner effects on natural productivity of mixed steelhead populations including spawners of hatchery and natural origin. It compared productivity in three mixed and reference (natural) population pairs, and estimated productivity as natural recruits per total spawners of natural and hatchery origin (R nat /S tot ) or as natural recruits per natural spawner (R nat /S nat ). Natural productivity estimated as R nat /S tot reflected hatchery program scale, not productive capacity of natal streams. This analytical approach masked natural production dynamics in populations with a major hatchery spawner proportion, and was therefore of limited use for determining hatchery spawner influence. Productivity estimated as R nat /S nat indicated similar productivity of reference and mixed populations, and an absence of hatchery spawner effect, in the case of (1) a large hatchery stray component, and (2) a hatchery supplementation program. In the third pairing, R nat /S nat productivity of the mixed population significantly exceeded that of the reference population, suggesting natural spawner abundance is below carrying capacity. Hatchery spawners contributed to natural productivity in that case, but in the presence of reduced natural spawner density. These findings suggest that hatchery spawners are unlikely to affect natural production of a mixed steelhead population unless natural spawner abundance is below carrying capacity.

Transfers of pink salmon (Oncorhynchus gorbuscha) eggs were made to the Qualicum River in two years, utilizing 5.79 million eggs from Cheakamus River stock in 1963 and 6.85 million eggs from Bear River stock in 1964. Adult returns to the Qualicum River were 100 spawners in 1965, 1967, and 1969; 11,940 in 1966; 3000 in 1968; and 300 in 1970. Differences between the odd- and even-year plants were noted in times of egg-take (equivalent to time of spawning of donor stock), incubation, and fry emigration, lengths of emigrating fry, possibility of losses through predation by herring on estuarine fry, and direction of orientation to the recipient (Qualicum River) stream. Pronounced differences between donor stock in rate of return are thought to be primarily related to differences in spawning times and stream temperature. The decrease in numbers of adults in the even-year generation may have been due to lower freshwater survival during incubation as a result of suspected superimposition of chum salmon on the earlier deposited pink salmon eggs; the loss was estimated to be in the order of 46%.

A comparison was made of the weights, lengths, weight–length relations, and chemical composition in migrating chum and sockeye fry resulting from eggs incubated and hatched in natural and artificial streams. Additionally, growth rates and rates of change in some chemical constituents were investigated in postmigrant channel- and river-hatched chum salmon confined to floating pens in sea water and in postmigrant sockeye salmon captured from their lake nursery area.There were no apparent differences in the lengths, weights, weight–length relations, or chemical composition between river- and channel-hatched chum salmon migrants. Nor was there any difference in the rates of change in length, weight, or chemical composition of these two groups of chums when confined to pens in sea water for 10 weeks after migration.There were differences in the weight–length relations, lipid content, and nitrogen content between channel- and river-hatched sockeye migrants. It is suggested, however, that these differences are due to the fact that the timing of the peaks of migration of these two groups of fish differed and that at any one time channel fry were physiologically different from river fry.Growth of the chum salmon in sea water and the sockeye in the lake was exponential and the slope of the weight–length relation, W = aLb, was approximately 3.25. During this growth period although total weight, moisture, solids, lipid, and nitrogen increased the rate of increase in moisture was less than the rates of increase in total weight or the other constituents.

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