Examination of DNA Profiles Reveals Close Kin Relationships and Provides a Tool for a Genomics Based Fishery Management Approach to Estimate Spawning Stock Biomass in Southern Bluefin Tuna

Estimated spawning stock biomass is a central measure for management of fisheries stocks and setting total allowable catch (TAC) quotas.  For the highly valued and depleted southern bluefin tuna (Thunnus maccoyii), conventional stock assessment methods provided reasonably precise estimates of relative depletion. Absolute abundance estimates however are much more uncertain, and quite sensitive to different assumptions about data inputs. For this species we present a genetic method to estimate absolute abundance of adult numbers (not the unrelated genetic concept of effective population size, Ne). The estimate is fishery independent and not subject to biases and interpretational problems associated with recent SBT assessments that incorporated catch or CPUE data. We explain statistical basis of this approach.  Our results based on analysis of DNA from 14,000 fish profiled using 25 microsatellite loci provide the first fisheries independent estimate of spawning biomass for a highly migratory stock. Furthermore, parent offspring pairs were tested using RAD sequencing and demonstrate this Next Generation Sequencing approach to be equally feasible for close kin analysis.  Our results indicate this genomics based fishery management approach has the potential to revolutionize monitoring of highly migratory species and has wide ranging applications to terrestrial and marine populations.