www.environment.sa.gov.au/soe2003/biodiversity.pdf
Not worth downloading the whole PDF, so here you go !!
There are a number of introduced freshwater fishes
that are having a significant impact on freshwater
ecosystems in South Australia. These species compete
with native fish for food and habitat and can adversely
affect water quality. There is limited comprehensive
information on the distribution and extent of these
species and so it is difficult to predict trends.
Those of primary concern are the European Carp,
Eastern Gambusia (or Mosquitofish), Redfin (or
European) Perch, Rainbow Trout, Brown Trout and
Tench.
Release of any of these species following
capture
is illegal under the Fisheries Act 1982.
At the end of the day, they are basically just another carp ! Eat it, use it for bait, fertiliser what ever ever you want, just DONT put it back in the water or you may well get a heafty fine slapped on you. People have mobile with video camera now and all they need to do is supply this to fisheries wih your number plate and you're gone.