UBC Theses and Dissertations

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UBC Theses and Dissertations

Pt. 1. Criteria and techniques of scale reading. Pt. 2. Life history of the steelhead Salmo gairdneri gairdneri Richardson as interpreted from the scales Maher, Frank P.

Abstract

Criteria for interpretation of scales of steelhead (Salmo gairdneri gairdneri) and for their use in back calculation of early life history were established. With these criteria, features of the life history of 784 steelhead from the anglers' catches of the Chilliwack River, B. C. were studied. Age composition of adult steelhead runs from 1948 to 1953 was uniform except for the suggestion of a slightly dominant year class, represented as 4 year old fish in 1950, 5 year old fish in 1951 and 6 year old fish in 1952. There was no suggestion that fish of any particular age, life history, sex or length tend to return as adults at any particular season of the year. The age and size of smolts at migration is variable, with the majority however in the 2 and 3 year age groups and ranging in size from 15 to 20 cms. Smolt migration usually occurs in March, with a small proportion of late migrants in August. Spawning frequency of adults was reviewed. Females generally spawn at an earlier age and more frequently than males. It is concluded that the variability in the life history of the steelhead acts as a safeguard in its conservation.

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