Sustainability Report 2006/07Case study: Tiny fish a large prize
Two days of netting and electro-fishing around Lancefield in February yielded the prize researchers were after – 157 of the nationally and state-threatened Yarra pygmy perch.
The survey, at six sites along Deep Creek, was commissioned by Melbourne Water freshwater ecologist Rhys Coleman.
“When Melbourne Water’s operating area was extended in 2005, it included the upper Maribyrnong River system,” he says. “Since then, we have been looking very carefully at the condition of the streams, learning about their values and threats to their health.”
It was known that Yarra pygmy perch, Nannoperca obscura, had been found in the Lancefield reaches of Deep Creek, an eastern tributary of the Maribyrnong.
Scientists found healthy populations at all six sites. The tiny native fish – usually four to six centimetres long – preferred shallow, calm pools with dense aquatic plants.
Reaches that had been fenced off from cattle contained more fish than those with direct stock access.
Rhys says threats to the species included loss of instream habitat diversity, stock access, vegetation clearing, the predatory habits of mosquitofish and redfin, and prolonged drought.
“Now that we have more information, we can think about our priorities to improve conditions and extend its habitat,” he says. “It’s an opportunity for us to work with the Deep Creek Landcare Group.”
The study recommends improving the quality and diversity of instream plants and habitat, fencing off the streamside banks, removing willows and other weeds, specific plantings on banks and a drought management plan.
Construction of a special offstream billabong would act as a haven and could help reintroduce the species into areas where it was historically found.
During 2007/08 we undertook a range of investigations including geomorphology studies of waterways in our extended operating area; Yarra River environmental flows; Dights Falls fish migration study; frog studies in the Bass River, French Island and Phillip Island; and surveyed platypus populations in the Bass River, Little River, Upper Maribyrnong River and Werribee River catchments.
We carried out pollution tracking surveys in the Stony Creek (Yarraville) and Elster Creek catchments, studied fish populations in the French Island, Mullum Mullum Creek, Tarago River and Bunyip River catchments, and developed an Upper Yarra riparian vegetation management plan.
Using helicopters and GPS-linked cameras, we recorded aerial survey details of about 740 kilometres of waterways within the Bunyip, Lang Lang, Dandenong and Koo Wee Rup catchments. Similar footage captured from previous projects was used to assist in weed mapping, identify erosion sites and fish barriers, for works planning and to locate important drought refuge areas.