Population structure of a deep-water squaloid shark, the Portuguese dogfish (Centroscymnus coelolepis)

The genetic population structure of the deep-water squaloid Centroscymnus coelolepis (the Portuguese dogfish) in the eastern Atlantic was investigated using eight polymorphic nuclear microsatellite markers and a 496-bp fragment of the mitochondrial DNA control region (mtDNA CR). Samples (20– 50 individuals per location) were collected off Ireland, Portugal, Madeira, Mauritania, South Africa, and the Azores (Mid-Atlantic Ridge). High levels of genetic diversity were found at the nuclear microsatellite loci (mean A ¼ 17.3; overall Ho ¼ 0.77), although there was low diversity at the mtDNA CR (h ¼ 0.65, p ¼ 0.0018). Genetic diversity for the Portuguese dogfish was homogeneously distributed among sampling locations, resulting in low and non-significant indices of genetic differentiation (e.g. FST ¼ 20.0013 to 0.0096, FST ¼ 20.017 to 0.033; p . 0.5), consistent with the absence of population structure within the area sampled. The results indicate that C. coelolepis has a high dispersal potential within the eastern Atlantic, and its apparent spatial segregation by size and maturity stage suggest large-scale migration associated with the reproductive cycle.