Field Performance of Two Commercial Strains of Rainbow Trout (Oncorhynchus mykiss) in Four Small Put-and-Take Alberta Fisheries
Both the Lyndon and Silver commercial strains of rainbow trout performed relatively well under field conditions characteristic of many small put-and-take fisheries in Alberta. There was no strong evidence of differential survival between the two strains; angler harvest alone could account for 100% of rainbow trout mortality at most ponds. Although condition of both strains declined significantly post stocking, the strains maintained acceptable condition as evidenced by reported high angler harvest and satisfaction with their catch. The most noteworthy difference between the two strains was the rate of tag reporting by anglers. Half of all Silver strain tag reports occurred within the first two weeks after stocking, but it took nearly twice as long for the Lyndon strain to achieve a comparable reporting rate. Gillnet catch of the Silver strain was also two to four times that of the Lyndon strain even when stocking densities were comparable. Different rainbow trout genotypes can vary greatly in their vulnerability to fishing gear (Biro and Post 2008), which could explain the apparent discrepancy between Lyndon and Silver strain capture rates observed in this study. If correct, such pronounced differences in vulnerability to fishing gear exhibited by these two commercial strains of rainbow trout have the potential to greatly impact fisheries as a result of their stocking. Given the relatively small size of the fisheries studied, unusual behaviour by just a handful of individuals could bias estimates based on samples aggregated across multiple ponds. Future assessments based on tag-returns should strive to obtain pond-specific rates of angler tag reporting and removal. Millions of rainbow trout of various strains are cultured in Alberta every year, differences in field performance among commercial strains, like those observed in this study have potentially large implications for the quality and efficiency of Alberta’s trout stocking program.