Comparison of microsatellite variability in wild and cultured tench (Tinca tinca)

The tench is a cyprinid fish species of increasing interest for European pond aquaculture. However, only little is known on the population genetic structure of this species; the few studies conducted so far were based on allozyme polymorphisms. In the present study, tench specific microsatellites were used for a genetic comparison of two wild populations and four cultured strains from Germany and Czech Republic. Seven out of nine loci analysed were polymorphic with a total number of alleles ranging from 2 (locus MTT-2) to 19 (locus MTT-9). Wild populations showed a higher allelic richness than the cultured strains (3.73 vs. 2.43) but this difference was still not significant (P = 0.062). Observed heterozygosity (0.370 vs. 0.366) and gene diversity (0.403 vs. 0.343) were globally similar in wild and cultured tench. In contrast to the variability within populations, genetic differentiation was significant between all of them as estimated by FST values from pairwise comparisons. The differentiation of the two wild populations (FST of 0.024) was lower than the average differentiation of the four cultured strains (mean FST of 0.159) but again this difference was not significant (P = 0.143). The present results indicate a tendency towards a reduction in variability within and an increase in differentiation between cultured strains in comparison to wild populations. To verify this, more populations have to be analysed. However, it is already evident that wild tench populations should be protected since they represent valuable genetic resources.