A new study has found New Zealand's freshwater fish numbers are in decline.

About 75 percent of our freshwater fish are listed as threatened or at risk - compared to the global average of 37 percent.

Intensive agriculture is believed to be having the greatest toll on numbers.

Lead study author and ecologist Mike Joy told Mike Hosking our native fish have no protection at all.

"A lot of these fish are migratory fish and they just can't get to the habitat because of dams and weir the most recent thing is to put out some guidelines, well nobody takes any notice of guidelines, we need to start getting tougher on these things."

LISTEN ABOVE AS MIKE JOY SPEAKS WITH MIKE HOSKING