Stock Identification of Columbia River Chinook Salmon and Steelhead Trout, 1984-1985 Annual Report.

Abstract

Fish were collected from 60 stocks of chinook salmon and 62 stocks of steelhead trout. Electrophoretic analyses were completed on 43 stocks of chinook salmon and 41 stocks of steelhead trout and meristic counts were completed on 43 stocks of chinook and 41 stocks of steelhead. Statistical comparisons between year classes of our electrophoretic data indicate that most enzyme systems are stable over time but some may be dynamic and should be used with caution in our analyses. We also compared neighboring stocks of both spring chinook and steelhead trout. These comparisons were between stocks of the same race from adjacent stream systems and/or hatcheries. Differences in isozyme gene frequencies can be used to estimate genetic segregation between pairs of stocks. Analysis of the chinook data suggests that, as expected, the number of statistically significant differences in isozyme gene frequencies increases as the geographic distance between stocks increases. The results from comparisons between adjacent steelhead stocks were inconclusive and must await final analysis with more data. Cluster analyses using either isozyme gene frequencies or meristic characters both tended to group the chinook and steelhead stocks by geographic areas and by race and both methods resulted in generally similar grouping patterns. However, cluster analyses using isozyme gene frequencies produced more clusters than the analyses using meristic characters probably because of the greater number of electrophoretic characters compared to the number of meristic characters. Heterozygosity values for each stock were computed using the isozyme gene frequencies. The highest heterozygosity values for chinook were observed in summer chinook and the hatchery stocks while the lowest values were observed in the spring chinook and wild stocks. The results of comparisons of heterozygosity values among areas were inconclusive. The steelhead heterozygosity values were higher in the winter stocks than in the summer stocks and similar between hatchery and wild stocks. Heterozygosity values among the areas were very similar for the steelhead stocks. Analysis of variance tests indicate that significant differences exist among the stocks for scales in the lateral series, scale rows above the lateral line, anal rays, dorsal rays, vertebrae and paired fin rays for both steelhead and chinook. Tests on gill raker and branchiostegal counts will be conducted when those counts are completed. Morphometric characters were compared between fed and starved groups of steelhead trout to determine which characters may be affected by condition factor or fatness of the fish. The results show that the linear characters, some head measurements and the truss-type characters in the caudal peduncle are most likely to be unaffected by condition factor. The measurements in the gut area of the fish appear to be unsuitable for discriminating among the stocks since they are highly affected by condition factor.