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Racial analysis of Skeena River steelhead trout (Salmo gairdneri) by scale pattern features

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Title: Racial analysis of Skeena River steelhead trout (Salmo gairdneri) by scale pattern features
Author: Cox-Rogers, Steven Frank
Degree Master of Science - MSc
Program Zoology
Copyright Date: 1985
Subject Keywords Scales (Fishes); Fishes - Racial analysis; Steelhead (Fish); Fishes - British Columbia - Skeena River
Abstract: The feasibility of using freshwater and first marine year scale patterns to identify component stocks of steelhead trout (Salmo gairdneri) in the Skeena River was investigated. Scale samples and sex and size data were attained from adult steelhead originating from five Skeena River tributaries (Zymoetz, Kispiox, Morice-Bulkley, Babine, Sustut) over a series of different years. Adult scale samples were also collected from the 1984 incidental steelhead catch in the Area 4 commercial salmon fishery for potential stock classification purposes. Significant differences in scale pattern growth, age composition, and sizes at age were found between the five Skeena River steelhead stocks. Linear discriminant function analysis indicated that the five stocks could be classified to correct river of origin with between 45% and 62% average classification accuracy (range Zymoetz 29%-60%, Kispiox 35%-60%, Morice-Bulkley 44%-76%, Babine 54%-64%, Sustut 56%-72%) depending upon the classification model used. Juvenile morphometric analysis for three of the stocks (Kispiox, Morice-Bulkley, Zymoetz) indicated the presence of significant between stock differences in standardized body form. These results support the notion that Skeena River steelhead exist as quantifiably discrete stocks. Classifying the 1984 mixed stock commercial fishery catches to probable stock of origin indicated that distinct peaks of stock abundance and run-timing occur through the fishery. In general, Morice-Bulkley and Sustut River steelhead were predicted to be most abundant with run-timings during the earlier portions of the fishery. Kispiox, Babine, and Zymoetz River steelhead were predicted to be less abundant with later run-timings through the fishery. Potential commercial fishery impacts to steelhead are briefly discussed. These observations suggest that the technique of scale patterns is a feasible method for stock separation in Skeena River steelhead. Further study is required to clarify yearly variance in the technique and to better establish stock specific differences.
URI: http://hdl.handle.net/2429/24598
Series/Report no. UBC Retrospective Theses Digitization Project [http://www.library.ubc.ca/archives/retro_theses/]
Scholarly Level: Graduate

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