Genetic Stock Identification of the Flathead Grey Mullet (Mugil cephalus) in Lake Tiberias Based on ParentOffspring Relationship

Abstract

The Lake Tiberias (Sea of Galilee) grey mullet (Mugil cephalus) population originates from translocated wild-caught, or hatchery-reared, fish. The aim of the study was to identify the taxonomic status and stock origin of a sample of 32 mullet individuals caught in the Sea of Galilee, based on the mitochondrial Cytochrome Oxidase I (COI) sequence analysis and nuclear microsatellite markers. A total of 13 microsatellite markers were selected from nine different linkage groups with a number of alleles ranging from 5-23, with an average of 9.85 alleles/locus. By using COI sequences and the Barcode of Life Data (BOLD) identification system, seven individuals were taxonomically classified as Thinlip grey mullet (Liza ramda) and the remaining 25 as M. cephalus. Of 663 nucleotides, 122 (18.4%) differed between the COI sequences of the two distinct mullet species. A preliminary parentage analysis of the hatchery-reared stocking batch, based on 13 markers, assigned them as progeny of three mating pairs. These three mating pairs only were tested as potential parents of the 25 M. cephalus individuals captured from the lake. Marker-based comparison showed that a parent-offspring relationship was rejected for 17 M. cephalus individuals by at least four genetic markers. Eight of 25 M. cephalus individuals (32%), were identified as progeny of the three parental pairs with the overall probability of 3.88 x 10-7 for correspondence by chance to any of these three parental pairs. The 13 markers used has high statistical power to reject a putative parent-offspring relationship obtained by chance thus resulting in familial identification. This approach represents an accurate method of genetic stock identification and should also be applicable to populations of other species. The results confirm that the mullet hatcheryreared fingerlings survived in the Sea of Galilee when released alongside wildcaught fingerlings.