We developed four microsatellite DNA loci to test for multiple paternity of black rockfish, Sebastes inermis, from the Seto Inland Sea of Japan. All loci showed a high degree of polymorphism (number of alleles per locus = 10-14, expected heterozygosity = 0.80) and discriminating power (probability of identity index = 3.71 9 10 -6 , exclusion probability = 0.999) in unrelated wild specimens (n = 32). Genotypic assignment of five dams (109-220 mm in total length) and 50 embryos from each dam (n = 50) indicated that four dams were mated with a single sire. Only for one dam and three of her embryos we could not exclude multiple paternity.
To enhance the stock of black rockˆsh, Sebastes inermis, 2 cm-, 3 cm-and 5 cm-size groups of hatchery-reared sh were released in a Zostera belt around Ikuno Island after marking with ALC andˆn cut. The larger the size, the farther from the release point they were recaptured and the better the survival rate. Especially, most of the 2 cm-sizeˆsh had disappeared about one month later. A predation test in a terrestrial tank conˆrmed that the redˆn velvetˆsh Hypodytes rubripinnis was a dominant species as a predator at the release point, and signiˆcantly preyed on the 2 cm-size group more than the 3 cm-size group. According to changes of triglycerides in the muscle of 2 cmand 5 cm-size groups after release, it took about one month for releasedˆsh to acclimate to the natural conditions.
This study is the first to report on the high occurrence of agglutinated pelvic fin membrane deformities in hatchery-reared black rockfish Sebastes inermis . For 5 years, this symptom was marked in hatchery-reared fish, with 58.7% of fish deformed on average (varying between 46.7 and 72.0%). The deformity was a peculiarity in hatchery-reared fish, but is negated in wild fish, and was not related to whether the fish broodstock originated from the wild or from a hatchery. Markrelease experiments showed that deformed fish were almost the same as normal hatchery-reared fish in growth and survival rates, and, theoretically, the recapture numbers of hatchery-stocked fish, estimated by deformity, almost coincided with actual recapture numbers, confirmed by otolith tagging. The results of the present study indicate that deformity in hatchery-reared black rockfish is useful as a stock separation tool.
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