The New Relatives of Whitebait

Forest and Bird, Issue 310, 1 November 2003, Page 8

The New Relatives of Whitebait

RMMcDOWALL

R.M. MCDOWALL

Scientist

reports on the discovery

of ‘new’ freshwater fish.

Shaded, bush stréam,'a prime habitat for native fish.

ll whitebait tend to look alike. Even when they grow into small adult ish they can look quite similar. These native fish, which include common whitebait and their relatives such as kokopu, kaoro and mudfish, all belong to a group called galaxiids. They live in freshwater streams, though many migrate to the marine environment to breed, hence the run of various whitebait in our rivers. Science is presently proving New Zealand has many more species of these galaxiids than formerly thought. When I finished my university training in the 1960s, writing a thesis on the taxonomy of New Zealand’s galaxiid fauna, I recognised only 14 species. Subsequent studies, soon afterwards, reduced that number to only 13. Personally, I thought every thing was ‘neat and tidy and that it was time to move on to the galaxiids of other lands — Patagonian South America, Australia, southern Africa, and so on. What a different perspective we have now! I got it wrong, and have spent nearly the last decade reconsidering and revisiting the situation. As of May 2003, we recognised no less than 22 galaxiid species, an increase of around three quarters, and from time to time I ask myself how I was so wrong. I can imagine that conservationists and naturalists also are wondering what is

going on. Some might ask: "Does it really matter?’ but in my view, it matters a great deal — a good understanding of biodiversity is really crucial to effective conservation. If we do not know what species are out there, and where they are distributed, it is impossible to plan to protect our biodiversity and our natural heritage. In some ways the process of scientific discovery is as interesting as the product. This discovery of ‘new species stems from when Colin Townsend arrived as Professor of Zoology at the University of Otago in the late 1980s. He established a Long Term Ecological Research Project on the Taieri River, where his group began to see differences in the ecology of the so-called ‘Galaxias vulgaris. There seemed to be two different ecological forms in the Taieri which also looked different. Specimens were given to Graham Wallis, a geneticist at Otago University, and he found them to be genetically different. Moreover, in one small stream the two forms were present together, indicating that they were looking at two distinct species (there was minimal hybridisation going on). One of these species turned out to be Stokell’s G. anomalus, which we now call ‘roundhead galaxias, and the other an undescribed species that was named

G. depressiceps, or ‘flathead galaxias’ At the time, we thought that these two forms were widespread across Otago and Southland. On the basis of the separation of these two forms, I returned to a peculiar population I knew of from the Waipori River that was also quite distinctive and ended up describing two more species, G. pullus, which we call ‘dusky galaxias, and G. eldoni referred to as ‘Eldon’s galaxias. Another oddity turned up in Stewart Island, a ‘dark little fellow with big round eyes who sometimes frequents a swamp, and so we called it G. gollumoides. Meanwhile, the geneticists pressed on with broad-scale sampling across the eastern South Island of the Galaxias vulgaris ‘complex’, as this group of fishes has become known. The genetic diversity seemed to explode. Part of this work showed our view — that flathead and roundhead galaxias were widespread across Otago and Southland — was wrong. Instead, another five galaxiids were identified. How many of these will eventually be recognised as distinct species has yet to be decided. All these changes demonstrate the value of a multi-disciplinary approach to questions about biodiversity — with taxonomists, geneticists, ecologists, biogeographers and geologists all playing a

The Variety of New Zealand Galaxtiids

role in clarifying understandings. What this collaboration is showing for freshwater fishes is paralleled by what others are finding in albatrosses and lizards, and various other groups. Taxonomic change has not ended there, however. Charles Mitchell found a rather odd-looking, undescribed galaxiid on the Chatham Islands, which he named G. rekohua, though ongoing studies indicate that it is really a form of Neochanna mudfish. Nick Ling and Dianne Gleeson were looking at mudfish genetics and came across a new lineage in the Kerikeri area, ‘smack-bang’ in the middle of the range of black mudfish, N. diversus. They named the new form N. heleios, which I call ‘burgundy mudfish’ owing to its deep reddish lower surfaces. There is yet more! We knew for more than 25 years about a population of longjaw galaxias in the Kauru River (a Kakanui River tributary) inland from Oamaru. We thought it belonged with Galaxias prognathus, but we never really looked at the fish carefully — as one longjaw looks rather like another longjaw, we never suspected anything odd. But geneticist Jon Waters at Otago University

found that these were actually a different kind of longjaw which is greatly different genetically. This drove us to look more carefully, and prove its difference — and now the Kauru fish is known as the lowland longjaw, G. cobitinis. The fish turns out to also be quite widespread through the mid and lower Waitaki River. Soon afterwards Simon Elkington of the Department of Conservation in Twizel phoned and said ‘I have this peculiarlooking alpine galaxias — you'll probably say it is just an alpine!’ but by this time I’'d become somewhat ‘sensitised’ to the likelihood that it really might be something odd, and it’s just as well. As a result, yet another new species is being added to our galaxiid fauna. This one we refer to as ‘bignose galaxias’ for reasons that are obvious to anyone who knows galaxiids. Were it not for Simon’s knowledge and alertness, we would probably just have gone on calling the fish alpine galaxias, and thought no more of it, missing a really fascinating bit of biodiversity. This species is proving to be quite widespread in the Mackenzie Basin. This story of species discovery had an interesting beginning. A farmer had a small wetland and became sick of getting bogged

in it, so he drained it. Having done so, he found that there was not enough moisture to get his grass to grow, and so then sought a resource consent to pump water from a pond and stream, back onto his pasture. To get a resource consent, he needed to get DoC approval, and it was in the process of checking out the fish fauna in the stream that Simon Elkington first noticed the bignose galaxias. It is hard not to think: ‘Wouldn't have been better if the wetland had never been drained, in the first place?’ — except that we might not have discovered the species. For those interested in New Zealand’s natural history and conservation it is impossible to emphasise how important these discoveries are. These additional

species are not just names on a list, but the evidence for the evolutionary processes that created our country’s animal and plant species. The interplay between taxonomists, geneticists, geologists and conservationists, allows us to, in part, unravel this history. For DoC, there is a real challenge in ensuring this biodiversity is protected. For me personally, this is what makes natural history so fascinating — exploring the distributions of the various life forms, and seeing how these match events in our geological history.

can be contacted at the National

Institute of Water and Atmospheric Research, P.O. Box 8602, Christchurch