An examination of the post-planting success of hatchery brook charr possessing different mitochondrial DNA haplotypes

Previous mtDNA and allozyme studies of brook charr Salvelinus fontinalis fr om northern Ontario lakes that had been extensively stocked with a governme nt hatchery strain, yielded results that were incongruous with a neutral th eory of selection in the mtDNA genome. A single haplotype (haplotype 1) pre dominated in all the fish sampled from these lakes, which is consistent wit h the observed distribution of this haplotype in northern portions of the s pecies range. However, haplotype I does not occur in a high frequency withi n the hatchery strain., In a direct survivorship experiment, of 1500 fish s tocked into an Ontario lake in the spring of 1994 containing a native popul ation of brook charr, no significant differences between stocking and recap ture mtDNA distributions were observed in the summer of 1994. However, a su rvey of young of the year in the following spring did not reveal the presen ce of any 'private' hatchery haplotypes. Significant differences in the dis tribution of mtDNA haplotypes were observed in two stocked lakes,compared t o those in the putative source hatchery strain. Haplotype I predominated in both these stocked lakes, suggesting that fish with this haplotype possess ed increased survivorship. (C) 2001 The Fisheries Society of the British Is les.