Life returns to a stream

00:26, Jan 24 2014

A South Canterbury stream once written off as a trout fishery because of dairy farming is again attracting anglers, thanks to the efforts of farmers and the community to keep stock out and replant the stream banks.

Before intensive irrigated dairy farming arrived, the Waikakahi Stream was something of a local anglers' secret, far less known than the nearby Waitaki, but renowned for the quality of its trout.

"They were reported to be 'the best fish in the country' and they had a particularly dark orange flesh supposedly because of the freshwater crayfish (koura) that they preyed upon," said Fish and Game officer Graeme Hughes.

But that changed, Hughes said, about a decade ago when suddenly the koura disappeared and trout numbers plummeted.

"What brought it to our attention was a farmer wintered his cows in there without fences and they just crossed backwards and forwards and it was unrecognisable as a stream.

"We took it to ECan (Environment Canterbury) and said, 'look what's going on here'.


"The farmer was soundly reprimanded and we began a rehabilitation planting scheme for that particular area that was completely devastated with cows and runoff and there wasn't a plant round it - it was like a stream running through a muddy football field."

With stock now excluded and the riparian strip planted in native trees and shrubs, the Waikakahi has been transformed from a muddy, weed infested creek into a far healthier waterway.

"Within a short time he had up to about 90 per cent of the farmers co- operating which was pretty exceptional really and probably eight to nine years after this work started, the results were quite astounding," said Hughes.

The stream bed had deteriorated to the point where there was more than 30 centimetres of mud and silt but it's now much more like it used to be.

"Today you can walk up there and you're crunching along on gravel, the dense macrophyte (aquatic plant) beds are not as extensive as they were and the fish numbers and condition have increased," said Hughes.

"The water's clear, you can see the bottom and you can actually see fish in it.

"The planting has encouraged water fowl, we've got pukekos and mallard ducks and it all looks very nice and possibly as it should have been for the last decade."

A recent study by Cawthron Institute scientist Robin Holmes confirmed the Waikakahi is returning to health. The project concentrated on structural habitat of the stream rather than water quality.

"Basically it shows that habitat in the creek has gone from what was described as a ground zero farm ditch to now it's actually supporting a good fishery through the efforts of farmers," Holmes said.

"It definitely goes against the current tide ongoing in the media about dairy farmers and it's a nice example of Fish and Game and dairy farmers working together and coming up with a solution that everyone's happy with. The creek's gone from an A class fishery, down to a D class fishery and now it gets a C+."

Fencing and planting has stopped phosphate-loaded sediment getting into the stream but there are still water quality issues in the Waikakahi, because of nitrates derived from dairy farming.

"Aspects of water quality there have improved," said Holmes. "They've reduced the suspended sediment load of the stream which is having an effect on the physical habitat quality because all the fine silts haven't been deposited on the bed, and also they've reduced their E coli count.

"There is an issue with nitrate in that stream but the fish that can survive through that and get to an adult stage where they're not vulnerable to nitrate are doing really well."

Morven Glenavy Ikawai Irrigation company (MGI) chairman Robin Murphy said farmer shareholders now wanted to take the restoration to the next level and that it was important to keep monitoring the Waikakahi Stream.

"People are getting very efficient with the irrigation and also the nutrient loadings and how they put their fertiliser on. There's a whole big effort going in there and it's crucial to monitor that change to see what actually does happen.

"If we can save ourselves costs of putting nitrogen on or minimising nitrate loss and utilising it, that's got to be a very good option for the farming community."

Hughes said anglers were once again asking him where the good fishing spots are on the stream.

"I've probably been quoted somewhere as saying the stream is absolutely ruined and it's lost forever so I was quite surprised. Nine or 10 years may sound a long time but if you'd seen it prior and then in the middle and now, I think most people would be surprised. With some co-operation and direction, you can bring a stream back."

The Press