A juvenile black mudfish is glossy because, like all native galaxiid fish species, it has no scales. It has a distinctive snub nose. Photo: RNZ / Alison Ballance
Stella McQueen checks a fish trap for native fish. Photo: RNZ / Alison Ballance
Wetlands are difficult places to work. They are - not surprisingly- wet, muddy, hard to walk through and too often surrounded by an unwelcoming band of exotic vegetation such as blackberry and crack willows. And the wildlife that makes its home in wetlands is equally challenging: often small, dark and cryptic.
As part of its Arawai Kakariki wetland programme, the Department of Conservation is carrying out research in three major wetland complexes: Whangamarino wetland in the Waikato, Ō Tū Wharekai in Canterbury, and in New Zealand’s largest wetland, the Awarua-Waituna Wetlands in Southland. One objective is to carry out predator trapping to help protect threatened birds, and another objective is to develop ways of monitoring said birds.
This is where Stella McQueen comes in. Stella is a self-described native fish geek. She is the author of A Photographic Guide to Freshwater Fishes of New Zealand (New Holland 2013) and The New Zealand Native Freshwater Aquarium (Wet Sock Publications 2010), a regular correspondent on matters fishy during Nights with Bryan Crump, and also maintains the NZ Native Fish page on Facebook.
During the summer she works on various freshwater contracts, one of which is the spring-time monitoring of cryptic birds in the Whangamarino wetland. DOC wants to know if its predator trapping, which targets rats and mustelids, is benefiting the local populations of fernbird, spotless crake and bittern. The protocol is to spend five-minutes at pre-determined spots along a series of transect lines at different sites in the swamp, listening for fernbird calls. Then she plays spotless crake calls, in an effort to stimulate any nearby birds to reply. Bitterns are detected using recorders that are programmed to record at various times at dawn, dusk and during the night.
Department of Conservation ranger Kaitlyn Morrison holding an automated sound recorder used to monitor bitterns, which make a distinctive booming call. Photo: RNZ / Alison Ballance
I joined Stella for an afternoon listening for fernbirds and spotless crakes - and we did manage to hear one spotless crake churring, and a pair of fernbirds dueting with each other. Stella had also put out small fish traps, called minnow traps, overnight, and these caught a number of small black mudfish, a threatened Galaxid species which is one of five species of mudfish New Zealand.
Stella says that one of the distinguishing features of New Zealand’s native fish is their lack of scales. The mudfish are also able to survive periods out of the water; they are able to gulp air and absorb it through the lining of their mouth.
Black mudfish are found from the Waikato northwards, and have a threat status of ‘at risk – declining’. As well as declining water quality in the wetland due to nutrient and sediment run-off from surrounding farmland, pest fish are a problem, especially Gambusia (also known as mosquito fish) and koi carp.
Wetlands are some of New Zealand’s most threatened habitats. More than 90% of our wetlands have been drained or filled.
Other wetland stories that have featured on Our Changing World include the ecology of Waituna Lagoon, flipping lakes, and monitoring the quality of stream water flowing into Waituna lagoon.
The green trees in the foreground are crack willows lining the Whangamarino wetland, which covers 7000 hectares in the Waikato. Photo: RNZ / Alison Ballance
