Analysis of mtDNA indicates weak temporal genetic heterogeneity in pink salmon spawning runs in two rivers on Sakhalin Island

Both odd- and even-year pink salmon populations were sampled during the spa wning runs in Firsovka and Bakhura rivers on Sakhalin Island. Four collecti ons of 30 fish spaced at 2-week intervals were taken from each river in 2 c onsecutive years. Four restriction endonucleases were used to examine 2.15% of the mitochondrial genome. Eighteen variable sites and three types of in sertion defined 37 haplotypes among 449 fish. Heterogeneity tests showed hi ghly significant differences among temporal collections taken in the odd ye ar from Bakhura River, and no significant differences among temporal collec tions from the other three spawning runs. However, probabilities of homogen eity among temporal collections were low in all tests, and an integral esti mate of the probability of homogeneity for the total set of tests was less than 0.001, indicating highly significant overall temporal heterogeneity. A nalysis of molecular variance (AMOVA), revealed that a small portion of the Variance was distributed among temporal collections, and small Phi(ST) val ues that differed significantly from zero only in the odd-year population i n Bakhura River. Temporal differences in spawning are probably adapative, a nd allow greater productivity in areas of high spawning densities. (C) 1999 The Fisheries Society of the British Isles.