Anglers becoming endangered species on some Canterbury rivers

Rising nitrate levels in drinking water have dominated Canterbury's water quality debate, but anglers, conservationists and scientists are also worried about the environmental effects, with many rivers and streams testing well above the national bottom line. In the third of a three-part series, Keiller MacDuff reports on the people fighting for the health of the region's waterways, which they say are being degraded by a toxic combination of water being taken for irrigation and nitrates in the service of intensive dairying.

Retired Canterbury fish veterinarian Peter Trolove has been a keen angler since he was a boy but these days he is more likely to be dipping a sample jar into the water than a fishing line.

The Federation of Freshwater Anglers past president regularly traces a loop from his Rangitata Huts home to the Halswell River, stopping to take samples from more than a dozen rivers, streams and drains to record nitrate levels.

A walk along the banks of the Selwyn River ahead of his routine testing reveals the depressing reality of a once thriving river.

Photo: RNZ / Nate McKinnon

"I probably walked about two or three kilometres upstream, there are some good pools and the sun is such that you can see under the banks, and I didn't see a fish," he said.

"This river was considered one of the best trout fishing rivers in the Dominion prior World War Two. Up until the 1970s, about 40,000 trout would go through the traps and now they'd be on the numbers of one hand."

Trolove trained as a veterinarian then worked for the dairy industry before heading overseas to retrain as a specialist fish vet, earning a masters in aquatic veterinary pathology.

He blames intensive dairy farming and a lack of central and local government leadership for declining Canterbury fish stocks.

"I was a dairy vet, I come off a farm, if there was a solution, I'd tell you. The hard truth of it is, you've got to farm less intensively," he said.

Photo: RNZ

A moss-covered sign at the Chamberlain's Ford entrance to the Selwyn River warns of high levels of toxic algal bloom, a neurotoxin that can be harmful to people and lethal for dogs.

The sign is barely visible, hidden by foliage as tall as the sign itself, an