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Significance of certain scale characters in the recognition of Fraser River sockeye races Hamilton, James Arthur Roy

Abstract

The Fraser River sockeye population is segregated geographically into a number of individual races. The scales of these fish contain several characters which might be used in the identification of these races. They are number of annuli (winter "checks"), number of first season and second season rings, additional "checks", and general appearance of scales. With few exceptions the Fraser River sockeye are of the 4₂ age group. Birkenhead River, Cultus Lake, and Chilko Lake sockeye have varying numbers of 5₃ fish. The Harrison River fish in general migrate immediately to sea as fry. The Pitt River sockeye in general return as 5₂ fish. Any difference that exists in ring counts between the sexes of sockeye is not significant. In general it was found that the younger sockeye (3₂) have greater numbers of first season lacustrine rings than do the 4₂ sockeye and that in turn the 4₂ fish have more rings than do the 5₂ fish. There is considerable variability from year to year in both first season and second season ring counts for each race. The greatest association in first season ring counts occurs on adjacent years. The ring counts between races within years are in many cases statistically different. The yearly variability within races and the overlapping in ring counts makes the separation of the races in a homogeneous population an impossibility. The ring counts of yearling migrant sockeye have fewer rings than do the adult sockeye of the same brood year. Most of the races have additional checks. On the basis of these studies it is impossible to segregate the various Fraser River races by using scale characters alone.

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