1 August 1999
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GROWTH AND GENETIC VARIATION IN HATCHERY-REARED LARVAL AND JUVENILE DOVER SOLE, SOLEA SOLEA (L.)
A. Exadactylos, A.J. Geffen, J.P. Thorpe-1999
Aquaculture, 176(3-4): 209-226 (from Current Contents)
Abstract:
The variation in multiple-locus and single-locus heterozygosity, and its correlation with growth rate, were examined in laboratory-reared juvenile Dover sole from two populations. The genetic structure of the populations was examined to test for genotype differences among individuals surviving past metamorphosis (70 days after hatching). Using enzyme electrophoresis, specimens were examined for 14 scorable loci, seven of them polymorphic. Larval growth rate was significantly affected by rearing treatment, but differences between treatments declined with age. Larvae from broodstock originating from the Irish Sea sole were larger at hatching, grew faster, and initiated metamorphosis earlier than larvae from broodstock originating from the Skagerrak-Kattegat Norwegian sole. The groups were indistinguishable on the basis of multilocus or single-locus heterozygosity and allele or genotype frequencies, after metamorphosis. Three measures of genetic diversity (percentage of loci polymorphic, number of alleles per locus and heterozygosity) were considerably lower than those of wild populations; batches from these sole hatcheries clearly demonstrated loss of genetic diversity, and marked changes in gene frequencies of cultured batches relative to the wild populations from which the parents were derived. Only two loci in the Norwegian sample were deficient in heterozygotes, whereas others exhibited heterozygote excess. These heterozygote excesses did not seem to be related to a particular allele or alleles. There was little evidence in this data set that the degree of multilocus or single-locus heterozygosity correlates with growth rate in S. solea. This conclusion agrees with the general observation that the correlation is not expected in populations where there is no heterozygote deficiency.
(Univ Liverpool, Port Erin Marine Lab, Port Erin IM9 6JA, Man, England, UK, e-mail of A.J. Geffen: geffen@liverpool.ac.uk)
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