Giant trevally (Caranx ignobilis) and bigeye trevally (Caranx sexfasciatus) are being considered as potential new species to enhance fisheries in lowland impoundments currently dominated by stocked barramundi. These species have the potential to create new fisheries that benefit regional economies in northern Australia. As part of a research project to evaluate the suitability of giant and bigeye trevally, a desk top study was conducted to determine the suitability and potential risks of stocking these species. The following were considered.
Both species of trevally were found to occur in Australian tropical freshwaters, and to be of low potential disease risk and unlikely to encounter temperatures outside their tolerance range in most large lowland impoundments. Genetic risks were considered manageable with appropriate hatchery protocols. If stocked at conservative densities it was thought that these species could provide viable fisheries without impacting negatively on existing prey species and fisheries in the dam, but this would require field-based trials to confirm this. Trevallies are unlikely to impact on threated species unless they run up tributary streams. This could be evaluated in a low-risk manner by acoustic tracking of sub-adult and small adult fish. As trevally cannot breed in freshwater any negative impacts can be reversed by ceasing stocking at the end of any stocking trial.