The population structure of olive flounder Paralichthys olivaceus was estimated using nine polymorphic microsatellite (MS) loci in 459 individuals collected from eight populations, including five wild and three hatchery populations in Korea. Genetic variation in hatchery (mean number of alleles per locus, A = 10.2-12.1; allelic richness, A(R) = 9.3-10.1; observed heterozygosity, H(O) = 0.766-0.805) and wild (mean number of alleles per locus, A = 11.8-19.6; allelic richness, A(R) = 10.9-16.1; observed heterozygosity, H(O) = 0.820-0.888) samples did not differ significantly, suggesting a sufficient level of genetic variation in these well-managed hatchery populations, which have not lost a substantial amount of genetic diversity. Neighbour-joining tree and principal component analyses showed that genetic separation between eastern and pooled western and southern wild populations in Korea was probably influenced by restricted gene flow between regional populations due to the barrier effects of sea currents. The pooled western and southern populations are genetically close, perhaps because larval dispersal may depend on warm currents. One wild population (sample from Wando) was genetically divergent from the main distribution, but it was genetically close to hatchery populations, indicating that the genetic composition of the studied populations may be affected by hydrographic conditions and the release of fish stocks. The estimated genetic population structure and potential applications of MS markers may aid in the proper management of P. olivaceus populations.

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The present study was conducted to evaluate the effects of dietary protein levels on growth, biometrics, hematology and body composition in juvenile parrot fish Oplegnathus fasciatus. Fish averaging 7.1 ± 0.06 g (mean ± SD) was randomly distributed into 15 net cages (each size: 60 9 40 9 90 cm, W 9 L 9 H) as groups of 20 fish. Five isocaloric diets (16.7 kJ/g energy) were formulated to contain crude protein levels (CP) as 35 (CP 35), 40 (CP 40), 45 (CP 45), 50 (CP 50) and 60 % (CP 60) in the diets. Fish were fed one of the experimental diets at apparent satiation twice a day in triplicate groups. At the end of 8-week feeding trial, weight gain (WG) of fish fed with CP 50 and CP 60 diets were significantly higher than those of fish fed with CP 35 , CP 40 and CP 45 diets. Fish fed with CP 45 , CP 50 and CP 60 diets had higher feed efficiency (FE) and specific growth rate (SGR) than those of fish fed with CP 35 and CP 40 diets. Protein retention efficiency (PRE) decreased with increase of dietary protein levels among fish fed with the experimental diets. Wholebody crude protein and lipid contents increased with the dietary protein level up to CP 50 diet. In conclusion, analysis of variance (ANOVA) revealed that the optimum dietary protein level could be 50 % for maximum growth of juvenile parrot fish, while the broken-line analysis of WG suggested that the level could be 48.5 %, in a diet containing 16.7 kJ/g energy.

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Genetic differentiationin Pseudocaranx dentex caught in Tosa Bay was studied by an eleetrophoretic survey of 28 isozyme and protein loci. Genetic dimorphism was found among samples and the allele substitution was observed at two loci (SP-4* and SDH*). The genetic distance between them was 0,095, falling within a range of differentiation at the species level. The number of vertebrae showed a clear difference between the two types, 25 vs. 24. These data suggest that an undescribed species might be included in P. dentex in Japan, and emphasize the need for a taxonomical review of this species.

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