The Coho Salmon of Cultus Lake and Sweltzer Creek

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Abstract
A few hundred to one or two thousand cohoes enter Cultus Lake each year, while the Sweltzer Creek population below it is several times as large. "Jack" (age II) fish usually predominate over older male cohoes at the lake. Spawning in the lake or in tributary streams above yields downstream migrations of some hundreds of fry and, a year later, up to a few thousand yearling smolts. These, on the average, amount to 0.13 per cent of eggs in spawners, or only 3 smolts per female. This does not suffice to maintain the coho run into the lake, which is, therefore, heavily recruited from creek-bred fish each year. There are also a very few age-II seaward migrants, which largely return from the sea the same year. Of yearling smolts marked in 1927, 8 per cent returned to the lake after one and a half year's absence.A large fraction, probably the majority, of yearlings produced in the lake fail to migrate from it and live there into their second or third year of life. They are readily taken by trolling or netting in the autumn of their second year and in the winter and spring of their third. Maturing fish of ages II (males) and III (both sexes) have been taken but they are scarce. For this or other reasons production of young by lake-resident cohoes is negligible, or perhaps altogether lacking.

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