UC San Diego

The leopard shark (Triakis semifasciata) is a common nearshore benthic elasmobranch endemic to the Pacific coast of North America, from Samish Bay, Washington, USA to Mazatlan, Mexico. Leopard sharks aggregate at specific coastal locations in the spring and summer, but little is known about leopard shark movement patterns once aggregations disperse. As a result, the extent of potential gene flow remains to be fully elucidated. Five microsatellite markers were used to analyze the genetic population structure of T. semifasciata throughout much of its range. Fin clips were collected from six locations in California and one location in Mexico (total n= 382). Analyses of the genetic data show a significant pattern of isolation by distance and structuring among several locations. Overall, pairwise differentiation tests showed a general pattern of northern California populations being significantly different than southern California populations. We conclude that T. semifasciata does not form one panmictic population and significant population structure is present. While T. semifasciata is not currently a threatened species, understanding gene flow throughout the species' range may provide insight into the population structure of similar species