As the eggs hatch, larvae (baby) and juvenile fish often drift with the flow to more suitable nursery habitats where there is abundant food and optimal water quality, as well as refuge from potential predators. Juvenile fish also use water flow for re-colonisation movement cues.
For the past 5 years, researchers from the University of Canberra have been investigating the role of water for the environment in boosting native fish spawning and recruitment in the mid to lower Lachlan, above and below Lake Cargelligo.
Over six weeks from mid-October to mid-December each year, the larval fish research team deploy light traps (cylinders with flow sticks in them to attract the larval fish) and drift nets over night and then sift through samples the next day looking for native larval fish species. These larval fish are often smaller than 6 mm. The live samples are then put into jars of ethanol, enabling these fishes to be preserved for identification, measurements and research later back in the lab.
Highlights to date include eel-tailed catfish from one site upstream of Lake Cargelligo near Kiacatoo late November 2018, which may drift into Sheet of Water and Lake Curlew, with catfish habitat. During the same sampling period, Murray cod were the most abundant species captured at all sites with good numbers of larval flatheaded gudgeon and Australian Smelt, with only a handful of the alien species, gambusia and no larval carp detected!
The larval work is all part of the Commonwealth Environmental Water Office (CEWO) Lachlan Long Term Intervention Monitoring (LTIM) Project, which also undertakes vegetation, productivity (food availability) and waterbird breeding if it occurs. All of the reports from this project are available at www.environment.gov.au/water/cewo/catchment/lachlan/monitoring