Saving the mudfish

GORDONTON ecologist David Riddell has been out fishing this week – and getting some big hauls of a fish most people have never seen.

He and fellow Kessels Ecology ecologists Dr Jennifer Blair and Gerry Kessels are rescuing a population of rare black mudfish which lie in the path of the new Waikato Expressway section between Rangiriri and Te Kauwhata.

David found the population back in 2009 while carrying out a preliminary ecological survey in the early days of the expressway project.

“They’re found in just a very small area, along about 120 metres of drain at the head of a gully,” he says. “Below that section there’s a broken culvert where the water falls from an overhanging pipe, and that stops eels and mosquitofish from invading their habitat and eating the mudfish. And unfortunately it’s right in the path of the new expressway.”

David and Jennifer set 13 minnow traps and two fine-meshed Fyke nets along the drain on Monday, and have been out every day this week to collect and measure the fish they’ve caught. The catch rates have been among the highest recorded for the species, with 231 caught over the first three days, of which 107 were caught on Thursday alone.

“We were hoping the numbers would drop off as the week went on, but it looks like there are still plenty left,” he says.

The fish are being taken to Waikato University where they are housed in a series of concrete water troughs planted with native wetland vegetation and through which water is circulated. The troughs had been set up for an earlier study on mudfish, but were currently unoccupied. The fish will be held there until new wetland areas adjacent to their lost habitat can be constructed. Ultimately, the mudfish should end up with more habitat than they started with.

Black mudfish belong to the same family as whitebait, and are one of five mudfish species unique to New Zealand. They are able to survive in places where the water dries up in summer, by burrowing down into the mud and waiting for the water to return. This means they can survive in places where no other fish can.

They used to be found in wetlands over much of the northern North Island, but with the draining of wetlands their range has been reduced by about 95 percent. Their strongholds are now in the large Waikato wetlands such as Whangamarino and Piako, but David says it’s important to protect these small isolated populations.

“They’re a special part of the New Zealand fauna, with a unique way of life . These gully heads used to be an important habitat for them but with land use changes they’ve all but disappeared from most of the places they used to be.”

The Waikato Times came out to do a story on the transfer, click here to read it.

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