High genetic connectivity in the Atlantic sharpnose shark, Rhizoprionodon terraenovae, from the southeast Gulf of Mexico inferred from AFLP fingerprinting

摘要

Elasmobranch species represent valuable fishery resources worldwide. Even though their life-history characteristics make them vulnerable to overfishing, there is insufficient fundamental knowledge about their stock structure in many exploited species. The Atlantic sharpnose shark Rhizoprionodon terraenovae is a small shark representing up to 45.9% of the annual landings from the artisanal elasmobranch fishery in the Gulf of Mexico. There is a need to assess the biological and genetic status of its populations to provide a basis for their proper management and conservation. We examined the genetic diversity and population genetic structure of R. terraenovae landed in three locations in the southeast Gulf of Mexico using amplified fragment length polymorphisms (AFLPs) fingerprinting. A total of 465 loci were detected using 3 primer combinations, 410 of which were polymorphic. The percentage of polymorphic loci was 96.3% and average expected heterozygosity was 0.327 for all localities. AMOVA and Bayesian analyses of genetic structure did not reveal significant genetic differentiation among the three localities. Our results are consistent with the migratory behavior and the lack of significant barriers to dispersal that may cause the high levels of genetic connectivity. We suggest that Atlantic sharpnose shark catches landed in the southeast Gulf of Mexico come from a large and well-mixed population, probably mating offshore; however, determining the spatial extent of this population requires a geographically wider genetic survey