Genetic diversity and differentiation of velvet belly lanternshark (Etmopterus spinax) in the Northeast Atlantic

Abstract

Deep-sea sharks are little resilient to targeted harvesting and bycatch fisheries due to their life history strategy characterized by slow growth, late sexual maturity, low fecundity, and few offspring. The Northeast Atlantic component of Etmopterus spinax is an example of a species where substantial population changes in terms of abundances have occurred due to intensive fisheries induced mortality. This has led to the IUCN categorization of E. spinax as Vulnerable with a negative population trend. To reverse the trend, management and conservation criteria are needed. To give management advice, knowledge about the connectivity between potential populations need to be improved, together with an understanding of their habitat and life history. In this study, the potential populations and differences between the locations sampled in the NE Atlantic, and particularly Norway, are studied by analyzing the mitochondrial NADH2 gene. Overall, at all locations the haplotype diversity is moderate to high, and the nucleotide diversity low. This can indicate relatively recent population expansion. The results also show significant population structure between the Norwegian locations and the rest of NE Atlantic. On a smaller scale, there was weak population structure within Norway and none for the rest. Against expectations, no genetic difference was found between a fjord and coastal population off Trondheim, NO. The lack of identifying genetic differences and population structure can be due to migration, or that NADH2 is not a suitable marker to identify this on a relatively small scale.