Population genetic structure of New Zealand blue cod (Parapercis colias) based on mitochondrial and microsatellite DNA markers
Parapercis colias (blue cod) is an endemic temperate reef fish that supports an important commercial and recreational fishery in New Zealand. However, concerns have been raised about localized stock depletion, and multiple lines of evidence have suggested P. colias may form several biologically distinct populations within the New Zealand Exclusive Economic Zone. Mark and recapture studies along with otolith and stable isotope studies have indicated that individuals are sedentary with very limited movement beyond the scale of 10-20km. The primary goal of this research was to advance the current knowledge of P. colias population genetic structure. This information can be incorporated into stock assessment models with the aim of improving the management of the P. colias fishery. This study made use of 454 pyrosequencing technology to isolate and develop the first set of microsatellite DNA markers for P. colias. These seven microsatellite loci, along with mitochondrial control region sequences, were used to determine the levels of genetic variation and differentiation between sites around the New Zealand coastline, including the Chatham Islands. Significant differentiation was observed between the Chatham Islands and mainland New Zealand sample sites, indicating that these two regions form distinct populations. Interpretation of the results for the mainland sites was more complex. Mitochondrial sequence data detected no significant pairwise differentiation between mainland sites, although a pattern of isolation-by-distance was observed. However, evidence for genetic differentiation among mainland sites was weak based on the microsatellite DNA analysis. Although pairwise Gѕт levels were significant in some sites, this was not reflected in principal component analysis or Bayesian structure analysis. It is likely that through long range dispersal, migration is at or above the threshold for genetic connectivity, but below a level necessary for demographic connectivity. This is indicated by both the genetic structure reported here, along with previous studies showing limited dispersal of P. colias.