Euro carp are a real problem in Aus waterways..I was so happy to see this Pacific heron spear right through the baaastard!
Sorry old mate..Carp by their sucking/feeding actions have been proven to be detrimental to the root system of OUR trees in the inland river systems. Namely the Murray/Darling and their tributaries.Muddy coloured water is doing no harm to the river, as for undercutting banks, carp don't eat tree roots.
Australia as a whole may hate carp, but they didn't arrive naturally so you can only blame yourselves.
All you need to do to thin them out is find a predator that loves eating them, and I"m pretty sure your
not short of suitable predators.