Freshwater fish species under threat

New Zealand streams and rivers are under strain and there might be no more freshwater fish species left in 40 years, warns a visiting expert.

Massey University freshwater fish ecologist Dr Mike Joy was in Nelson on Wednesday to give a talk about what he says is a crisis facing New Zealand rivers.

Dr Joy said there were "two completely different worlds" in New Zealand's rivers.

"There's the one world that I read about in Ministry of Environment and State of Environment reports telling me that everything's good and I don't need to worry and it's all rosy. But every time I go out to rivers I see [algal growth] as a result of too much nutrient in the river," he said.

"I see more and more signs saying, `You can't swim here, take shellfish or fish here'. Then I have all these really keen young students coming up through the system who want to go and study native fish, and I can't find them."

Half of New Zealand's native fish are currently on the threatened species list. Dr Joy said his research showed that in the past 10 years there had been a steep decline of native fish species, particularly in streams in urban and pastoral areas. "By 2050, we won't have any native fish left, if this trend keeps going."

He said government state-of-the-environment reporting "would be laughable if it wasn't so sad". Sampling was pointless in a flowing river, and studying individual elements such as phosphorus, clarity, temperature and oxygen levels was a waste of time.

"The other, much easier way to do it is to look at the animals that live in the river.

"You could measure all the stuff in this room to see if we could survive in it, or you could just look in here and see whether we're alive or not."

A 2005 Tasman District Council state of the environment report said all larger rivers in the region had "good water quality" during times of drier weather. However, the report said that when river flows were high as a result of rain, some rivers, and occasionally marine beaches, were not safe to swim in because of pollutants from farms and houses.

District council resource scientist Trevor James told the meeting that he concurred with a lot of what Dr Joy said about degradation of habitats, issues with small streams and the amount of disturbance.

"We're not monitoring the change in that habitat adequately," he said.

"Part of that is because we don't have any national monitoring protocols. They've only just been released and so we'll be getting on to that."

He said the Tasman district was lucky because half the land area was covered in native forest. "We're getting a lot of clean water coming down, diluting the contamination, so we don't have to worry so much about water quality. In some catchments, sediment discharges are a problem in parts of the region, but in general it's not so bad."

He said after 15 years, dairy-farm effluent had been turned around, but there was "a raft of other issues", such as loss of stream habitat.

Nelson City Council environmental monitoring co-ordinator Paul Sheldon said Dr Joy's belief that sampling was pointless was "probably overstating the case".

He said the city council was aware of a gap and was rectifying that. "Up until the last three years, we haven't been doing much on freshwater fish," he said.

"The national profile on freshwater fish was increasing and we were aware our programme really didn't adequately cover that. It covered the habitat, but that's only one thing."

The Tasman District Council is currently consulting on part of its waterways resource management plan. Submissions close on August 21 and forms are downloadable at tasman.govt.nz.

- © Fairfax NZ News