Genetic patchiness among recruits of Girella elevata: spatial and temporal variation in genetic composition

Understanding the magnitude and pattern of connections among populations and the temporal variation in these patterns are essential for the design, implementation and administration of fisheries stock management and... [ view full abstract ]

Understanding the magnitude and pattern of connections among populations and the temporal variation in these patterns are essential for the design, implementation and administration of fisheries stock management and conservation strategies. Investigating the intra and inter year genetic variation of recruitment will increase our understanding of the repercussions of variation in recruitment success and yield important spatial and mechanistic insights into patterns of larval dispersal. To explore this, we examined the spatial and temporal variation in population genetic structure of adult and recently settled juvenile populations (from 3 years) of Girella elevata using microsatellite markers. Girella elevata, is a large (up to 76cm) long-lived species that has a range between 27°S and 39°S on the east coast of Australia which experiences considerable recreational fishing pressure throughout this geographical range and has recently been shown to have high levels of residency. The proportion of the total genetic variation attributable to differences between regions and locations (~800km) for the adults was effectively zero (Fst=0.008). In contrast, the juveniles showed significant heterogeneity in allele frequencies among years and in some cases reduced genetic diversity when compared to the adult populations indicative of sweepstakes recruitment. This result suggests that the adults, with several year-classes, are capable of maintaining a panmictic population over large spatial scales despite the genetic distinctiveness of individual year-classes at fine spatial scales. This result has implications for the management of marine populations as temporal variability in recruitment may act to promote long term stability of populations, it is therefore essential that management strategies account for this variability.