16 Jun 2017

Canaries of the Waterways

From Country Life, 9:20 pm on 16 June 2017

When caddisflies, mayflies and stoneflies thrive in waterways it's a sign water quality is good. Recently, farmers visiting NIWA's site at the National Agricultural Fieldays were shown how to spot the bugs.

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Photo: supplied NIWA

NIWA set up an eye-level stream at Fieldays complete with flowing water, fish, insects, leaves, twigs, stones and rocks.

Freshwater ecologist Brian Smith had been out catching the bugs for the exhibit - a selection of stoneflies, caddisflies and mayflies.

The insects are considered to be the 'canaries of the waterways' as they are the first to disappear in a polluted environment.

Brian hoped farmers would go home, turn over rocks in their streams and look at them with different eyes.

"I think people would be very surprised in a nice clean, cool water stream, at the diversity. A diverse stream is a good stream. That's what we strive for in our restoration projects."

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Photo: RNZ/Carol Stiles

He says caddisflies have remarkable attributes like being able to spin silk that hardens underwater. The silk's being investigated to see if it could be used for medicinal purposes.

"We have caddisflies that spin nets, so they have a net like a fishing line...we have other ones that build amazing cases made of small sand grains or one that cuts up a bit of grass and makes a..beautiful case made of grass fragments."

Brian says New Zealand has 250 species of caddisflies, 50 species of mayflies and 110 species of stoneflies.

"They don't occur anywhere else in the world so they're unique to New Zealand and we want to preserve that and where they don't occur, with our habitat restoration, we want to encourage them into these new habitats."