Broad scale population connectivity of the Eastern Rock Lobster, Sagmariasus verreauxi

The commercially important Eastern Rock Lobster, Sagmariasus verreauxi, has a disjunct distribution along the coastal areas of NZ and NSW, and is also occasionally found in the waters off Tasmania. A long planktonic larval... [ view full abstract ]

The commercially important Eastern Rock Lobster, Sagmariasus verreauxi, has a disjunct distribution along the coastal areas of NZ and NSW, and is also occasionally found in the waters off Tasmania. A long planktonic larval phase, which in S. verreauxi spans 8-12 months, has traditionally been thought to facilitate long-range dispersal via ocean currents creating a high level of gene flow and connectivity across the geographic range of the species. However several recent studies on rock lobster species with similar pelagic larval phases have been found to exhibit fine scale genetic structure and self-recruitment illustrating that population structure cannot always be predicted based on pelagic larval durations. Population structure and the connectivity of S. verreauxi throughout its range is yet to be clearly understood, however there is preliminary evidence that suggests a genetic break could occur between NSW and NZ populations. As such the S. verreauxi fishery is currently managed as two single, genetically independent stocks in NSW and NZ. This study used single nucleotide polymorphisms (SNPs) to investigate the genetic structure and population connectivity of 90 S. verreauxi individuals collected throughout its range (NSW, NZ and Tasmania). DNA was sequenced with the reduced representation genomic approach of double digest Restriction Associated DNA Sequencing (ddRAD-seq). 417 million reads were obtained from 2 lanes of a HiSeq run with an average of 4 million reads per individual. SNP data was obtained using a maximum likelihood statistical model through the program STACKS. Outlier loci were identified with Lositan and removed from the dataset. The resulting SNP data was analysed for population subdivision with both a Bayesian clustering method (Structure) and a Discriminant Analysis of Principal Components (DAPC), with genetic connectivity being assessed via assignment testing. Levels of population connectivity determined for S. verreauxi between NSW, NZ and Tasmania will be presented and placed in the context of our current understanding of hydrodynamics within the study area.