Angling advocates are vocal about the need to maintain water quality, but I don't think they acknowledge the negative impact sport has on our native fish.
New Zealanders value biodiversity, but we're struggling with a plethora of issues affecting our waterway flora and fauna.
In many cases we're trying to work out how we can undo more than 100 years of land use change, town sewage discharges and impacts from introduced sports, pest fish and wildfowl.
A recent international book on trout has a chapter by Niwa scientists documenting the impact brown trout have on our native fish. They're our most common exotic freshwater fish, and according to the authors the science shows brown trout can eat their way through native fish, such as whitebait, koaro and glaxias at an amazing rate, and have significant deleterious effects on native biodiversity.
They've been called the stoat of our waterways. Native galaxias were plentiful in streams without brown trout, but in neighbouring waterways with brown trout they had been decimated, irrespective of the land use around the waterways.