ARE CULTURED STOCKS OF BROWN TROUT (SALMO-TRUTTA) AND RAINBOW-TROUT (ONCORHYNCHUS-MYKISS) GENETICALLY SIMILAR TO THEIR SOURCE POPULATIONS

The Ontario Ministry of Natural Resources (OMNR) implemented a controlled breeding program in the early 1980's with the objective of culturing fish that are genetically representative of the source populations. We describe the OMNR brookstock management plan for brown trout (Salmo trutta) and rainbow trout (Oncorhynchus mykiss) and test its effectiveness by comparing the allozyme variation of the source fish collected from the Ganaraska River, Ontario to several descendant hatchery lines. Ancestral and descendant rainbow trout do not show significantly different allele frequencies. However, significant differences were detected in brown trout. The absence of several rare alleles in hatchery fish can be explained by sampling error rather than inappropriate propagation methods. Hatchery stocks of either species do not show reduced enzyme heterozygosity compared to wild fish suggesting that the OMNR hatchery system has been successful in retaining allelic variation during broodstock founding and propagation.