Fish & Game wants the government to resurrect an abandoned national standard for water flows, in response to new research on the effects of extracting water from rivers.
The study, by Nelson's Cawthron Institute, found that the authorities have been drastically underestimating how much water trout and salmon need to grow and thrive.
Fish & Game chief executive Bryce Johnson said the government should rethink its approach to monitoring water flows.
"The government actually did set up a group to set up a national environmental standard for flows some years ago, but it never finished its work.
"I think what this piece of research shold do is convince (Environment Minister) Nick Smith that he needs to resurrect that national environmental standard and get it up on the radar again."