engleski

Genetic structure of greater amberjack Seriola dumerili (RISSO, 1810) populations in the Mediterranean Sea

Due to its high growth performance and market value, the greater amberjack (Seriola dumerili) is a promising species for aquaculture in the Mediterranean. Although captive breeding started in the 1980s, industrial production in closed rearing facilities is relatively new. Farmed fish are usually produced from relatively few broodstock individuals with limited genetic diversity so that the genetic composition of these populations differs significantly from the natural population. In addition, net-pen farming and escapes can lead to a range of socio-economic and ecological interactions in the coastal zone. In the present study, a total of 479 wild and farmed individuals of Seriola dumerili collected between 2013 and 2021 in the western and central Mediterranean Sea were genotyped with 15 microsatellite loci in two microsatellite multiplexes. Observed and expected heterozygosity varied among populations (0.65-0.76 for Ho ; 0.65- 0.73 for He), with farmed populations having significantly lower allelic richness (4.6 vs. 6.8) than wild populations. The farmed populations had significantly higher observed heterozygosity (0.70 vs. 0.66) and lower inbreeding coefficient (FIS) (-0.14 vs. -0.01), which was due to excessive heterozygosity at several loci. The high FST differentiation index of 0.114 was observed among farmed populations and differed significantly from the low index observed in the wild populations (0.008). Farmed populations were characterized by very low effective population sizes (Ne < 10 individuals), in contrast to the overall estimates of Ne > 1000 individuals for the wild populations. Initial Structure analysis of the dataset revealed K = 2. Examination of the additional structural signal at K = 5 revealed that all farmed populations were assigned to a separate cluster with some degree of admixture. These results are consistent with previous findings for species with a much longer history of farming. To maintain the genetic diversity of a wild population, it is important from an ecological point of view to obtain information on the origin of the farmed populations to avoid the introduction of foreign alleles that could alter the genetic structure of the wild populations. Escaped farmed fish pose a conservation problem because of the risk of erosion of genetic structure, loss of local adaptive genetic variation, or complete replacement of wild populations by farmed populations. It is recommended to use local hatchery stocks wherever possible to minimize the potential disturbance of locally adapted populations by escaped farmed fish.

Seriola dumerili ; aquaculture ; escapes ; Mediterranean Sea

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