Barfin flounder and spotted halibut have been selected as target species for stock enhancement in Japan. Understanding the genetic condition of the wild stock is a principal requirement in any stock enhancement program. The genetic variability of barfin flounder and spotted halibut, and the population structure of spotted halibut were evaluated using microsatellite DNA markers (msDNA) and the control region of the mitocondrial DNA (mtDNA). Barfin flounder and spotted halibut showed high genetic variability at the msDNA level. Barfin flounder A was 16.7 and H e was 0.860; spotted halibut A n ranged from 7.7 to 10.2 and H e ranged from 0.710 to 0.774. At the mtDNA level, high haplotype (h = 0.922) and low nucleotide (π = 0.002) diversities were observed for barfin flounder; however, low haplotype and nucleotide diversities (h = 0.603-0.620 and π = 0.001-0.002), and very low haplotype and nucleotide diversities (h = 0.193 and π = 0.0003) were observed for spotted halibut in the north and south locations, respectively. Slight genetic differentiation among spotted halibut sampling locations was observed from the msDNA. MtDNA analyses showed genetic differentiation between north and south locations, but not within them. The designation of north-specific and south-specific management units in the future stock enhancement activities of spotted halibut is recommended.
Spotted halibut Verasper variegatus hatchery juveniles produced in 2002 were genotyped using three microsatellite DNA markers (msDNA) and then released into natural waters. Subsequently, recaptured individuals were examined using msDNA. In order to evaluate the effectiveness of the stock enhancement program, from the genetic point of view, a pairwise F ST test was implemented to estimate the genetic divergence between the wild captive broodstock, the hatchery offspring and the recaptured samples. The analysis showed significant differentiation between the broodstock and recaptured samples. Pedigree determination using msDNA was used to calculate the effective population size of the recaptured stock, which was found to be very low (N e ≈ 8). Equal family survivability was observed between the two recaptured stocks, but not between the released and recaptured stock. The number of identified families was higher and more equalized in the hatchery offspring compared to the recaptured samples, where the number of families declined. This fact was caused by an unequal family survivability just before or just after release. Separately, the number of contributing parents to the hatchery offspring was lower than the broodstock census number. Consequently, these two facts caused the genetic divergence of the recaptured stock from the broodstock.KEY WORDS: effective population size, hatchery stock, pedigree tracing, recaptured fish, spotted halibut, stock enhancement, survival rate.
The barfin flounder has been recently declared to be rare, as the number of wild individuals in Japan has greatly reduced since 1975. The Japanese National Center for Stock Enhancement started the stocking program for this species on 1987. In the present study, microsatellite DNA loci were applied in order to determine the pedigree of the hatchery-produced juveniles for stock enhancement. Additionally, using six polymorphic microsatellite markers, the accuracy to assign dyads to categories of kinship was estimated using the relatedness estimator (R XY ), similarity indexes (individual genetic identity [GI] and proportion of shared alleles [P S ]), identification of kin groups using unweighted pair group method with arithmetic mean (UPGMA) clustering based on interindividual genetic distances (1-R XY , 1-P S , and 1-GI), a likelihood ratio approach, and partition methods to separate individuals into cohorts. The results were compared with the pedigree relationship previously obtained from parentage analysis. Estimation of the kinship relationship between individuals could be better inferred by means of UPGMA dendrogram clustering based on 1-GI or 1-P S as interindividual genetic distances, or using computer software to perform partitioning of set of individuals.
In relation to the stock enhancement program for barfin flounder, hatchery juveniles produced in 2001 were genotyped using microsatellite DNA markers (msDNA) and then released to natural waters. Subsequently, recaptured individuals, designated as 'tentative recaptured', were examined using msDNA. In order to evaluate the effectiveness of the stock enhancement program, pairwise F ST and genic differentiation tests were used to estimate the genetic divergence between the wild samples, the hatchery broodstock, and the tentative recaptured samples. Analysis showed significant differentiation among these three groups. Pedigree determination by msDNA was used to establish the origin of the tentative recaptured individuals, in order to elucidate whether they were hatchery produced, 'real recaptured', or wild specimens. Wild individuals were not found. The effective population size of the real recaptured stock was very low (N e = 16.6). Equal family survivability was observed between the released and real recaptured stocks, indicating that the genetic variability of the released stock was maintained in the natural environment. Future broodstock management, breeding designs, and family contribution equalization of the offspring to be released will be required in this rare species to avoid unintended genetic differentiation between the wild population and the hatchery broodstock.KEY WORDS: effective population size, hatchery stock, pedigree tracing, rare species, recaptured fish, stock enhancement, survival rate.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.
hi@scite.ai
10624 S. Eastern Ave., Ste. A-614
Henderson, NV 89052, USA
Copyright © 2024 scite LLC. All rights reserved.
Made with 💙 for researchers
Part of the Research Solutions Family.