Data from: Evidence for interannual variation in genetic structure of Dungeness crab (Cancer magister) along the California Current System

Using a combination of population- and individual-based analytical approaches, we provide a comprehensive examination of genetic connectivity of Dungeness crab (Cancer magister) along ~1,200 km of the California Current System (CCS). We sampled individuals at 33 sites in 2012 to establish a baseline of genetic diversity and hierarchal population genetic structure, and then assessed inter-annual variability in our estimates by sampling again in 2014. Genetic diversity showed little variation among sites or across years. In 2012, we observed weak genetic differentiation among sites (FST range = -0.005 – 0.014) following a pattern of isolation by distance (IBD), and significantly high relatedness among individuals within nine sampling sites. In 2014, pairwise FST estimates were lower (FST range = -0.014 – 0.007), there was no spatial autocorrelation, and fewer sights had significant evidence of relatedness. Based on these findings, we propose that inter-annual variation in the physical oceanographic conditions of the CCS influence larval recruitment and thus gene flow, contributing to inter-annual variation in population genetic structure. Estimates of effective population size (Ne) were large in both 2012 and 2014. Together, our results suggest that Dungeness crab in the CCS may constitute a single evolutionary population, though geographically limited dispersal results in an ephemeral signal of isolation by distance. Furthermore, our findings demonstrate that populations of marine organisms may be susceptible to temporal changes in population genetic structure over short time periods, thus inter-annual variability in population genetic measures should be considered