Parentage determination of black sea bream(Acanthopagrus schlegelii)for stock enhancement:effectiveness and loss of genetic variation

摘要

The stock enhancement programs for black sea bream Acanthopagrus schlegelii have been conducted in China for a fewyears.However,little information has been reported concerning the effectiveness and genetic effect of black sea bream stock enhancement.In order to detect the contribution of released individuals in Zhujiang River Estuary(ZRE)and Daya Bay(DB),six microsatellite markers were used to identify the hatchery-released individuals.In addition,this pedigree of hatchery populations(broodfish and hatchery-released offspring)was traced to detect the number of effective parents(N_(e)),the inbreeding coefficient and the decrease of genetic variability in the reproduction.The pedigree reconstruction showed that at least 69(out of 93)broodfish had offspring.The estimated N_(e) was 54.8,consequently the inbreeding coefficient was 0.91%.The genetic diversity of hatchery-released offspring was lower than that in that of broodfish(heterozygosity alleles,0.727-0.774),some alleles(number of alleles,61-69)and genetic variance were lost during reproduction.It was observed that wild samples had higher levels of genetic diversity compared with hatchery populations as well as recaptured samples in releasing area.A total of 128 hatchery-released black sea bream were identified among 487 recaptured samples in ZRE,while a total of 15 samples were identified among 96 samples in DB.In summary,there was a high survival of released fish.N_(e)vertheless,the results provided evidence to consider a loss of genetic variation in hatcheryreleased stock and a negative genetic effect of the stock enhancement.