E. Vázquez

Allozyme variation in natural populations of Atlantic salmon in Asturias (northern Spain)

Abstract This study describes the genetic variation (based on analysis of 24 protein-coding genes) within and between two natural salmon populations of Asturian rivers. Information on the genetic structure of populations at the southern distribution limit of Salmo salar in Europe is provided. In the natural populations, five of 24 protein-coding loci were polymorphic ( Aat-2 , Idh-3 , Mdh-3,4 , Sdh-1 and Sdh-2 ). Non-significant allele frequency differences were found between populations. At the Mdh-3,4 locus the frequency of the 87 allele is much higher than the values given for other European populations. The mean heterozygosity in these samples (based on 24 loci investigated) was 2.18%. Nevertheless, the amount of variability in Asturian natural populations is somewhat lower than the average estimated in the Atlantic salmon population.

Superior developmental stability of heterozygotes at enzyme loci in Salmo salar L.

Abstract The degree of heterozygosity of five enzymatic loci is related to the degree of fluctuating asymmetry of three bilateral traits in two farm stocks and in two natural populations of Salmo salar . In all cases we verified the existence of an inverse correlation of the degree of heterozygosity with the number of asymmetrical traits per individual as well as with the total magnitude of asymmetry that the individuals present. We also detected the association at the populational levels: a higher average populational heterozygosity implies a lower total magnitude of asymmetry. The phenomenon is general and the possibility that the correlation is due to the direct effect of a particular locus is excluded. The use of fluctuating asymmetry is proposed as an indicator of the loss of heterozygosity in salmon populations.

Heterozygosity-fitness correlations in the gilthead sea bream Sparus aurata using microsatellite loci from unknown and gene-rich genomic locations

Heterozygosity-fitness correlations (HFC) were assessed for a sample of a gilthead sea bream Sparus aurata population. Two hundred and seventy-one fish were genotyped at 22 known and novel microsatellite loci, from which correlations between the multilocus heterozygosity index (I(MLH) ) and various fitness traits (fork length, mass and specific growth rates) were calculated. Significant global HFCs were found in this sample (0·02 ≤r(2) ≤ 0·08). In addition, all the significant correlations found in this work were negative, indicating that heterozygotes had lower fitness than their homozygote counterparts. Marker location could not explain the observed HFCs. Evidence of inbreeding, outbreeding or population and family structuring was not found in this work. The presence of undetected general effects that may lead to the appearance of HFCs, however, cannot be ruled out. These results seem to be best explained by the occurrence of local effects (due to linkage) or even by possible direct locus advantages.

Microsatellites-based genetic analysis of the Lophiidae fish in Europe

The anglerfish species Lophius piscatorius and Lophius budegassa are among the most valuable fishes sought after by bottom fisheries in western and southern European waters. It is currently believed that there are two stocks for each of the two species, north and south, which determine their assessment and management. A genetic analysis using eight polymorphic microsatellite markers was carried out on samples collected from western European waters and the south-western Mediterranean Sea. The results strongly suggest that the boundary between northern and southern stocks is not genetically supported. However, populations were not genetically homogeneous. Besides a pattern of genetic differentiation between Mediterranean and the rest of the samples, the L. budegassa samples taken from the Spain Atlantic zone and from the Portugal Atlantic zone were genetically distinct, whereas the samples taken in the French Atlantic zone for the L. piscatorius species seem to be different from the rest of the samples under study. This can be indicative of a more subtle genetic structure that deserves more study for guaranteeing adequate fishery management of these species.

Genetic Status of Atlantic Salmon (Salmo salar) in Asturian Rivers (Northern Spain)

The Atlantic salmon (Salmo salar) is a species which occurs in rivers on both sides of the North Atlantic. In the last 40–50 years, man’s impact has resulted in a drastic decrease of this species throughout its native distribution and in some rivers it has disappeared. In order to choose an appropriate strategy for its conservation and management, a detailed knowledge both of the population structure and the amount and distribution of genetic variation throughout the geographical distribution range of the species is necessary (Stahl, 1983,1987; Ryman, 1983). In the last decade, several studies, using electrophoretical techniques, were carried out to provide information about the genetic diversity and structure of Atlantic salmon populations (Cross and Ward, 1980; Stahl, 1981, 1983, 1987; Vourinen, 1982; Ryman, 1983; Cross and King, 1983; Guyomard, 1987; Verspoor, 1988; Vourinen and Berg, 1989; Koljonen, 1989; Sanchez et al., 1991). However, few data on natural populations limited to southern Europe are available (Guyomard, 1987; Sanchez et al., 1991).