Population genetic structure of freshwater catfish (Tandanus tandanus) in the Murray-Darling Basin and coastal catchments of New South Wales: Implications for future re-stocking programs.
Rourke M and Gilligan D (2010) Population genetic structure of freshwater catfish (Tandanus tandanus) in the Murray-Darling Basin and coastal catchments of New South Wales: Implications for future re-stocking programs. Final report to the NSW Recreational Freshwater Fishing Trust for Project No. DPI FT48. Industry & Investment – Fisheries Final Report Series No. 123. 73pp.
Freshwater catfish (Tandanus tandanus) is a popular recreational freshwater fish species that was once widespread in eastern Australia. Over the last few decades, catfish have suffered a severe decline in abundance and distribution. This has resulted in very restrictive recreational fishing regulations across most of their distribution, including a zero bag limit for all western flowing NSW waters. These regulations are likely to remain unchanged unless there is a substantial recovery in catfish numbers that may allow a recreational fishery to be re-instated.
One potential method of increasing wild population size is by stocking rivers and impoundments with hatchery-bred fish. However, stocking of hatchery fish can in fact be detrimental to the wild population if considerable care is not taken to ensure the appropriate genetic ‘type’ of fish is released. Negative effects of stocking recorded in other species of fish include loss of genetic diversity, and loss of the original natural population. Nevertheless, stocking is recognised as an important tool for the management of threatened species, provided they are carefully planned and executed.
This project was implemented to clarify the natural population genetic structure of freshwater catfish across their range, which will be used to guide a future stocking program. Results indicated that catfish are not genetically uniform across the Murray-Darling Basin and coastal NSW catchments. As a result, three genetic zones were proposed in the Murray-Darling Basin and in seven in coastal catchments. If a river or dam is to be stocked in the future, broodfish should be collected from the same genetic zone to avoid any negative effects of stocking, and consequently help maximise the survival rate of stocked fish given they will be genetically suited to their release site.