Population Genetic Structure of the Night Shark (Carcharhinus signatus) in the Western Atlantic Assessed Using Nuclear Microsatellite Markers and Mitochondrial Control Region Sequences

The night shark is a deepwater, coastal and semi-oceanic shark found in the Western Atlantic and along the west coast of Africa. It prefers tropical and warm temperate waters near outer continental shelves in depths of 300-400m during the day and around 200m at night. The night shark is of conservation concern because it is an important component of artisanal fisheries and is heavily fished off Cuba and Brazil. The night shark was assessed as Vulnerable by the IUCN Redlist in 2006, and is prohibited from landings in US waters. No information on stock structure for the night shark exists to assist in its stock assessments and guide its overall management. We report on the population structure of the night shark utilizing the complete mitochondrial control region sequence (1066 bp) and 11 microsatellite loci from 72 individuals sampled from part of its western Atlantic range. Analysis of the night shark mitochondrial sequence data set collected thus far reveals strong geographic subdivision with two genetically distinct populations (NW Atlantic and SW Atlantic), and overall high levels of genetic diversity. We are expanding these analyses with larger sample sizes and will also report on comparative inferences made from the nuclear markers.