Fish & Game is planning a ban on winter sports fishing in some areas due to deteriorating water quality, which has some fisheries on the verge of collapse.

In what it called a "desperate measure", the group's North Canterbury branch said members supported a ban on sport fishing in some lowland waterways, as the fisheries were significantly depleted.

The proposed ban would involve closing the winter season, which runs from May to September, for lowland waterways east of State Highway One throughout North Canterbury.

It would affect fishing in parts of the Waimakariri River,  which Fish & Game says is the busiest recreational river in the South Island,  and the Selwyn River.

North Canterbury Fish & Game council chair Trevor Isitt said the fishery had suffered years of environmental degradation.

"We need to preserve what's left – the remaining spawning that still occurs in these waters – if we are to protect the fishery from complete collapse. 

"Sadly we are now seeing the end result of years of over allocation of water resources and deteriorating water quality from agricultural runoff and other forms of pollution."

A recent public meeting on the issue had attracted about 100 anglers, who unanimously agreed it was a necessary step to protect the fishery.

Canterbury's rivers have undergone years of declining water quality, particularly in areas close to Christchurch. The number of rivers suitable for swimming has reduced from 74 per cent five years ago to 64 per cent last year.

Dairy intensification in North Canterbury and Selwyn, combined with low river flows, are frequently cited as contributors to poor water quality.

Isitt said he did not believe a dramatic reduction in fish including trout was due to over-fishing, but instead directly attributable to poor water quality.

"It's quite clear that by any reasonable environmental standards, Environment Canterbury (ECan) has failed local people and anglers, by allowing inappropriate land uses such as continued intensified dairying which could not survive without irrigation.

"Water quality and freshwater habitats have been permitted to deteriorate far past the point where species like trout can comfortably breed and maintain their life cycles and populations."

It was just one regulatory measure from Fish & Game which needed to be followed up by ECan, he said.

Green Party water spokeswoman Catherine Delahunty commended Fish & Game for sending a strong message.

"It's really sad that Fish & Game have had to make this statement and that these rivers are no longer suitable for fishing," she said.

"In the last decade we've really trashed our rivers, and now the chickens are coming home to roost."

She said such stands were becoming necessary to fight declining water quality.

"They have to take a strong stand - we all do. Are we just a country where you can wade in rivers but you can't swim or fish, or are we a country which looks after its rivers properly?"

ECan director of science Tim Davie said there was widespread agreement that water quality had declined due to agricultural intensification.

ECan was trying to reverse the decline while providing for viable farming, which would take a long time, he said.

"This is not a quick fix. Degradation of lowland streams has taken decades to build up and will take many years to remedy."

He said ECan had created rules around nutrient discharge, introduced rules for farmers around meeting environmental standards, and endeavoured to restore ecosystems, which would all have an affect on freshwater quality.

It would continue to work with groups such as Fish & Game to improve water quality, he said.

"Fish and Game have been a supporter of the Canterbury Water Management Strategy and we want to continue working with them to achieve the community's aims of including improving the health of our lowland waterways."

 - Stuff