Mr Pahe said the awa was once filled with eel and was deep and clean. Now, there is a build up of algae in the swimming hole, a lack of eel and a water level that comes just above the ankles.
"It's worrying, especially seeing some of our tamariki in the awa. The food source of the awa is low, namely tuna. The river was full of eel and now there are very few," he said.
Mr Pahe said hapu members had some theories about why the health of the awa was declining but said they were researching to discover exact causes.
"Irrigation, the taking of water from the awa, farming and the development of the forestry industry have all had effects on the water. There was an issue with [one farmer] disposing cattle carcasses and farming effluent into the awa."
Mr Pahe said the hapu had formed a monitoring group to go up and down the awa and raise awareness.
"They are monitoring the awa completely legally. We are not physically stopping anyone but we are raising awareness and campaigning," he said.
Mr Pahe said the hapu are looking at holding public meetings that farmers and neighbours can attend, and will be talking to the Far North District Council about the issue.
Mr Pahe said Ngati Tautahi would also be holding hui with other hapu in the area to look at the possibility of placing the rahui on the entire awa.