A new report on New Zealand's freshwater biodiversity shows most species in rivers and lakes are under threat.
The Society for Conservation Biology released the report, which shows 74 percent of native freshwater fish, mussel and crayfish species are threatened with extinction.
Massey University fresh water ecologist Mike Joy, who contributed to the report, said excessive nutrient un-off from intensive agriculture was one of the main factors contributing to the problem.
Dr Joy said commercial exploitation of many threatened species and human and industrial waste discharged to waterways also contributed to freshwater species numbers dwindling fast.
"That means that they're just disappearing from where they've been for tens of thousands of years.
"We've had some really, really rapid changes, if you go back to the early 1990s, not more than 25 years ago, only a quarter of them were threatened species."
The report suggested six priorities to safe-guard biodiversity, including changing legislation to protect native species, and establishing monitoring and recovery plans for threatened invertebrate fauna.
The Government recently identified priorities and objectives to improve freshwater management in the National Policy Statement for Freshwater Management , however Dr Joy said the the problem had largely been ignored.
"There's a bunch of things that we could do immediately, obviously cutting back on land use and some of that intensification.
"The other crazy thing is the lack of legislation to protect native fish. Many of them, bizarrely, like the long fin eel and and four of the five whitebait species, are threatened species and yet they're commercially harvested and sold.
"It's just nuts you can go into a supermarket or restaurant and buy threatened species and eat them."
Dr Joy said urgent changes were needed to clean up the country's lakes and rivers.