Team gets to know tiny fish

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by Claire Allison

Scientists have just spent four days getting to know a tiny fish that lives only in the Mackenzie Basin.

One of New Zealand’s rarest native fish – the bignose galaxiid – was the subject of a four-day field study by Environment Canterbury science and biodiversity team members in the Mackenzie Basin this month, in order to better protect the tiny creatures.

The team was kept busy capturing, counting and measuring the small fish, as well as assessing its habitat at 11 sites in one catchment.

The field work is part of a five-year research project into how fencing stock away from waterways and riparian planting impacts the habitat of the species and is run in partnership with the owners of Gray’s Hill Station.

“We are looking into how bignose galaxiids respond to habitat change when stock and sediment inputs are excluded from its spring-fed habitat.” – Environment Canterbury biodiversity officer Rob Carson Iles

Environment Canterbury biodiversity officer Rob Carson Iles said the tiny fish, usually between 40mm and 80mm in length, were part of the same family of fish as native whitebait and mudfish.

“The bignose galaxiid lives only in the Mackenzie Basin and very little is known about them.

“Unlike inanga (whitebait) they don’t have to travel out to sea to complete their life cycle, so their whole world is in this local area. They are classified as nationally vulnerable so it’s important we understand what affects them.

“We are looking into how bignose galaxiids respond to habitat change when stock and sediment inputs are excluded from its spring-fed habitat.

“Aquatic and riparian plant growth is likely to increase as a result of the fencing, so it will be interesting to see how this affects the number, size or species of fish we are catching.

“The study is still in its first year, so although we have few results we are certainly gathering a lot of useful information.”

Other recent initiatives to help protect native galaxiids in the Waitaki River catchment include the placement of fish gates to keep out introduced predatory species, such as trout.

These projects have been supported by the Upper Waitaki water zone committee through Environment Canterbury’s Immediate Steps Programme, the Department of Conservation and the New Zealand Defence Force.