Swimming Stamina Differences Between Genotypically Distinct Forms of Rainbow (Salmo gairdneri) and Steelhead Trout

Abstract

Rainbow trout (Salmo gairdneri) homozygous for liver lactate dehydrogenase alleles ldhHα^A and ldhHα^B were artificially propagated and their swimming stamina compared. The time required to fatigue 50% of the Hα^AHα^A phenotypes in fixed water velocity tests was 2.3 times greater on the average than that of Hα^AHα^B phenotypes.Likewise, LDH phenotypes Hα^AHα^A, Hα^AHα^B, and Hα^AHα^B of steelhead trout from the Thompson River were artifically propagated and their swimming stamina compared. In contrast to the rainbow trout, significant differences in stamina among the three phenotypes of steelhead were not evident in the stocks from this river nor between phenotypes Hα^AHα^B and Hα^BHα^B from another stream, the Vedder River, which has a very low frequency of the ldhHα^A allele. The stamina of young steelhead from the Thompson River was, however, 3.8 times greater than that of those from the Vedder River. Key words: stamina, LDH, rainbow trout, steelhead, phenotype, swimming, fatigue