Capture and long-distance translocation of cleaner fish to control lice infestations on marine salmonid farms has the potential to influence wild populations via overexploitation in source regions, and introgression in recipient regions. Knowledge of population genetic structure is therefore required. We studied the genetics of ballan wrasse, a phenotypically diverse and extensively used cleaner fish, from 18 locations in Norway and Sweden, and from Galicia, Spain. We detected two very distinct genetic groups in Scandinavia, northwest and southeast. These groups were split by a stretch of sandy beaches in southwest Norway, representing a habitat discontinuity for this rocky shore associated benthic egg laying species. The Galician sample was highly differentiated from all Scandinavian samples, but overall closer to northwestern samples. . Distinct genetic differences were observed between sympatric spotty and plain phenotypes in Galicia, but not in Scandinavia. The mechanisms underlying the geographical patterns between phenotypes are discussed, but not identified. We conclude that extensive aquaculture-mediated translocation of ballan wrasse from Sweden and southern Norway, to western and middle Norway, has the potential to mix genetically distinct populations. These results question the sustainability of the current cleaner fish practice.

Genotype results for Scandinavian and Galician ballan wrasse (Labrus bergylta) genotyped for panel of 82 randomly selected SNPs. 

The dataset was the basis for population structure analysis and subsequent comparison between sampling locations in Scandinavia and Galicia, Spain, as well as between a subset of phenotype sorted samples from some Scandinavian locations and from Galicia. 

Dataset resulting from SNP genotyping on an Agena iPlex Platform, called in TyperAnalyzer