Population genetic structure of freshwater catfish.
Rourke M (2010) Population genetic structure of freshwater catfish. Presentation given at the 2010 Australian Society for Fish Biology Conference and Climate Change Symposium, 12 – 14 July 2010, Melbourne Museum, Victoria, Australia.
The freshwater catfish (Tandanus tandanus) is a popular recreational freshwater fish that was once widespread in eastern Australia. Stocking of rivers and impoundments has been raised as a possible solution to re-establish populations in the Murray-Darling Basin (MDB), though this can have negative genetic consequences for the wild population including loss of genetic diversity, and disruption of local adaptations. Careful planning and execution of stocking programs can increase numbers in the wild and minimise potentially negative genetic impacts. The genetic structure of freshwater catfish throughout the MDB and coastal populations of New South Wales (NSW) was assessed to inform a future stocking program. Fin-clips were collected from 821 freshwater catfish and were screened across eight microsatellite loci specifically developed for freshwater catfish. The mitochondrial control region was also sequenced in a subset of these samples. Results provided additional support for the presence of an undescribed cryptic species in the Bellinger, Macleay, Hastings and Manning catchments on the mid-north coast of NSW, and also suggested an additional undescribed cryptic species or subspecies in the Tweed, Brunswick, Richmond and Clarence catchments. Most coastal NSW catchments had substantial genetic differentiation from one another, owing to the lack of connection among most coastal rivers. In contrast, there was limited genetic differentiation among most MDB populations, which is most likely due to the high degree of river connectivity among MDB catchments. The only exceptions were a small number of genetically divergent populations naturally isolated above waterfalls, or populations established from translocated fish. Results of this study have helped identify broodstock genetic zones within NSW. These zones require stocked fish to be released into the same parental broodfish genetic location. This will ensure stocked fish are genetically similar to populations at the release site. This approach will minimise the negative effects of stocking and maximise the survival rate of stocked fish by ensuring they possess any local adaptations that may be present in the wild population.