Crossing Methodology and Genotypic Diversity in a Hatchery Strain of Rainbow Trout (Oncorhynchus mykiss)

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Abstract
Genotype frequencies and heterozygosity at nine polymorphic enzyme loci were determined in 720 rainbow trout (Oncorhynchus mykiss) produced by three types of crosses: full-sib family, diallel, and pooled gamete. Five pairs of parental fish were crossed by each method within each of three experiments. Offspring produced by pooled crosses deviated significantly from equal parental genetic contributions while those from the diallels did not. Significant deviation in full-sib family offspring is attributable to only a single locus in one experiment. The deviations in the pooled cross may be the result of unequal male contributions. Cross types also differed significantly in genotype frequencies. Crossing methodology has potentially important effects on the genetic variation of cultured fishes.