ABSTRACT
This study used 11 polymorphic nuclear microsatellite loci to determine the population connectivity of five geographically isolated populations of tope shark Galeorhinus galeus (Africa, Australia, North America, South America and western Europe). Genetic analyses revealed significant structure among all populations indicating a lack of population connectivity. These findings indicate that globally distributed populations of G. galeus are isolated and should be managed as distinct, independent stocks.
Subject(s)
Genetics, Population , Microsatellite Repeats , Sharks/genetics , Animals , Gene Flow , Genetic Variation , Sequence Analysis, DNAABSTRACT
In order to properly manage and conserve exploited shark species, detailed analyses of their population structure is needed. Global populations of Galeorhinus galeus are in decline due to the exploitation of the fishery over the past 80 years. Currently, the genetic structure of eastern Pacific populations of G. galeus is not known and recent observations in the northeastern Pacific suggest an increase in numbers. To evaluate gene flow among populations of G. galeus, 116 samples were collected and analysed from six geographically dispersed locations: Australia, North America, South Africa, South America (Argentina and Peru), and the UK. Analysis of 968 to 1006 bp of the 1068-bp mitochondrial control region revealed 38 unique haplotypes that were largely restricted to their collecting locality. Significant genetic structure was detected among populations (Phi(ST) = 0.84; P < 0.000001) and migration estimates were low (Nm = 0.05-0.97). Due to an apparent lack of migration, populations of G. galeus appear to be isolated from each other with little to no gene flow occurring among them. As a consequence of this isolation, increasing numbers of G. galeus in the northeastern Pacific can be best explained by local recruitment and not by input from geographically distant populations.
