MEPS 292:225-232 (2005)  -  doi:10.3354/meps292225

ABSTRACT: Samples of Todaropsis eblanae from throughout the species range in east Atlantic and Mediterranean waters were screened for genetic variability at 1 minisatellite and 4 microsatellite loci. Extremely high levels of variability were observed within samples at all loci, with the mean observed heterozygosity per locus ranging from 0.82 to 0.91. Tests of allele frequency heterogeneity and measures of F_ST (Wright’s fixation index) suggest that significant genetic differentiation occurs between samples taken in African waters and those taken in European waters (overall F_ST = 0.014, p < 0.001). Furthermore, significant differentiation was evident between the samples taken from South African waters and those taken from off Mauritania (between sample F_ST = 0.012, p < 0.001). More subtle structuring was suggested within the European samples, largely attributable to differences between the Mediterranean sample and Atlantic samples (within Europe F_ST = 0.002, p < 0.03). However, the high levels of heterozygosity associated with the examined loci means that biological implications of marginally significant statistical results must be considered. One consistent aspect of the observed variation is that the Mauritanian sample is more genetically differentiated from European samples than from the more geographically isolated South African sample. Homoplasy and historical events such as climatic cycles and post-glacial recolonisation are considered as possible explanations for the observed patterns of variation. In terms of stock structure, the findings suggest the presence of at least 3 genetically isolated populations in the east Atlantic, which has important implications for management and sustainability of this resource.

KEY WORDS: Todaropsis eblanae · Squid · Microsatellites · Minisatellites · Population genetics · Fisheries · Stocks