Microsatellite-based pedigree tracing in a Japanese flounder Paralichthys olivaceus hatchery strain: implications for hatchery management related to stock enhancement program

Abstract

Effective population size in captive populations is affected by several factors such as the number of contributing broodstock to the next generation, sex ratio of parents, and variations in family size, which can be accurately evaluated by examination of the pedigree structure in the populations of interest. Here we present an example of microsatellite-based pedigree tracing in a hatchery strain of Japanese flounder Paralichthys olivaceus to be stocked into natural sea areas. We also detail the potential effect of selective operations (size selection) on the pedigree structure. The hatchery strain we screened was founded by using 18 wild captives (6 males and 12 females) through the use of the mesocosm spawning method, and the pedigree of the offspring including 113 individual larvae collected within 24 h after hatching, 216 individuals of 1 month old, and 407 individuals of 4 month old was unambiguously identified. The contribution of candidate broodstock to the next generation was highly skewed as the contribution to almost all of the offspring was monopolized by a single male, and a half of the females did not produce any offspring. The contribution of one family to the released fish selected for larger size (total length) was significantly high, while those of other two families were low (P<0.008).