A lot of the wildlife in Australia is part of fragile ecosystems. Koi are big, tough and efficient eating machines that destroy ecosystems, eat all there is to eat, and then may even destroy the waters they inhabit (no kidding- koi often find food in the wild by eating away the mud banks of lakes and rivers to find worms and things to eat, incidentally this also makes the waters they inhabit shallower and eventually dry up over time, killing everything).
I strongly disagree. Whilst the European Carp disturbs the sediment, they would not be the sole cause of the shallowing of river beds which then dry.
There are many other factors involved with the degridation of Australias water courses, hence the statement made about them causing the drying of river beds due to their feeding habits is in-accurate.
They do increase sediment suspended in water, reducing available sunlight for aquatc plants and uproot them, hence a reduction in habitat for many native species. They also eat eggs, small fry, fish and insects native to the water course or catchment.
They can tolerate a wide variety of environmental conditions, from high and low salinity, extreme temperature conditions, low oxygen levels etc and they are tough as boots,. resulting in there proliferation.
They can reproduce in massive quantities several times a year. Their total fish biomass is said to represent 80% of all fish in Australias water courses, being found in every state of Australia, except for the NT (Northern Territory). The carps biomass can sometimes reach 95% of all fish species found in a river course or catchment.
It is illegal to return any carp back into the water after youve caught them. This guys didnt make it....
cheers
PESTS!!!!!!! they not pests!!! the koooooool!!! lol
got sum mirror carp in our pond ... i wish our carp wud eat anyfink .. der ded fussy eaters and only eat the dearest stuff 
