More homes for the Canterbury mudfish

Forest and Bird, Issue 295, 1 February 2000, Page 8

More homes for the Canterbury mudfish

Department of

Conservation.

Janine Gray

conservation covenant is the latest tool in the stategy to protect the endangered Canterbury mudfish. Landowners along Dog Kennel Stream, in South Canterbury near Waimate, have agreed to protect the wet areas to save the fish. The Canterbury mudfish is not as well known as other threatened native species in New Zealand, but lives in slow water, often undetected. One of four New Zealand mudfish species, the Canterbury mudfish is described as a ‘small, cryptic, galaxiid fish’ in the genus Neochanna. It is peculiar to Canterbury. The other New Zealand mudfish are: the brown mudfish which is widespread along the northern West Coast of the South Island and the southern half of the North Island; the black mudfish found further north around Kaitaia, in northern Taranaki, and at Waihi and on the Hauraki Plains; and a fourth species just recently described which is found in the northern North Island. Like the other mudfish species, the Canterbury mudfish has adapted to living in wetlands, swampy creeks and drains that tend to dry up in the summer. Today the fish occur in about 25 small, vulnerable, and separated habitats in the area between the catchments of the Ashley River in North Canterbury and the Waitaki River in South Canterbury. It is classed as a category B species for conservation action under the current Malloy and Davis ranking system, and is also listed by the International Union for the Conservation of Nature in its Red Data Book of endangered species. Ngai Tahu regard it as a taonga (treasured) species. The ability of the Canterbury mudfish to breathe through its skin when out of the water allows it to survive in some

droughts, and makes it rather special. A Department of Conservation freshwater specialist, Martin Rutledge, says the mudfish can dig into the mud and form a burrow-like structure which protects it from drying out for up to two or three months. Mudfish also take refuge under debris such as logs where there is more moisture. Provided they are in a moist place, mudfish are able to breathe oxygen through their skin. But unlike the lungfish species, they do not become dormant (that is they do not show true ‘aestivation mechanisms; such as slowing their metabolism down). Although the mudfish possess the unique quality of surviving with very little water, they do suffer the same problems as other native fish, both in New Zealand and worldwide. According to Martin Rutledge, the loss of the quantity and quality of its original habitat has been the primary cause of population decline. The once-extensive, lowlandkahikatea, swamp forest of Canterbury was probably the main habitat type for Canterbury mudfish. Now its primary swamp-forest habitat has been almost eliminated by drainage, channelling, and changed vegetation. The regular drag-lining of some stream habitats, to control weeds and remove sediments, places additional stress on some populations. Pugging by farm stock also considerably degrades the usefulness of waterside mud as a refuge in drought. The facts that the remaining habitats are small, and occur primarily on privately owned land, also makes protection difficult. Fortunately, the three landholders along Dog Kennel Stream have agreed the area will be managed by the Department of Conservation with several

conservation objectives in mind. The first is to protect and enhance the stream habitat to maintain and increase the mudfish population. The second is to protect and enhance the natural character of the land with particular regard to the natural functioning of ecosystems. The third objective is to protect and improve the water quality. To ensure these objectives are met, the Department of Conservation is responsible for planting native vegetation along the stream edge, removing weeds, and maintaining fences and floodgates. In turn the landholders are expected to allow DoC staff access to the stream. Nearly seven hectares will be covenanted, and six kilometres of fence have been erected to prevent stock-induced

bank erosion and protect riparian vegetation from grazing. This is one of the few areas that formally protects freshwater fish species on private land. Over the years the Department of Conservation has made significant progress in protecting and enhancing some key mudfish habitats in Canterbury: potential habitats have been surveyed, habitat enhanced, new populations found, and others established by translocating fish to suitable places. Other conservation initiatives include a conservation strategy — the Department of Conservation is presently preparing a formal recovery plan, covering Canterbury mudfish, and the other mudfish species found elsewhere.