hey matt, are there any smaller fish or other food source in the dam? how deep is it? you could stock silver perch, golden perch (murray darling strain), bass and saratoga (very expensive). You can buy all of those from Sunshine Coast Crayfish producers at yandina which is probably the closest fish hatchery to you.
contact info link:
http://www.sd.qld.gov.au/dsdweb/v3/g...count_id=35749
cheers,
Tim.