| Rainbow trout (Oncorhychus mykiss) of mixed origin have been present in the Great Lakes since the 1870s. The objective of this study was to determine if Lake Ontario rainbow trout are segregating into separate genetic units. Variation in the mitochondrial genome was used as a marker for hierarchical analysis of population structure. It demonstrated that: (1) naturalized rainbow trout are characterized by high genetic diversity, (2) sibling juveniles do not school exclusively together, (3) some regional heterogeneity may be developing, and (4) Ontario populations differ from those in New York both in haplotype frequency distribution and nucleon diversity.;A comparison of naturalized populations with current stocking strains revealed similarity between most New York "wild" and some cultured fish. Together with an historical review, results suggest that ecological conditions were more influential in shaping the development of Ontario populations established from early introductions. Recent massive stocking, however, likely had greater impact on the present character of New York populations than did ecological factors, although this stocking may have altered earlier genetic structure. |
