IMEF - Fish Monitoring 1999-2000
The Integrated Monitoring of Environmental Flows (IMEF) project was established by DLWC to assess the environmental responses to improved flows after the introduction in 1998 of the flow rules for the major regulated rivers and the Barwon-Darling River. This pamphlet provides an update on the fish component of IMEF.
Freshwater fish were selected as one of the environmental indicators to be examined as part of the monitoring program. The NSW Fisheries Office of Conservation is conducting the fish component of the IMEF program for the Department of Land and Water Conservation. This fish component of the program is designed to test the following potential environmental benefits of releases from dams and limits on extraction:
- The breeding of native fish could be promoted by ensuring more natural temperatures and keeping spawning habitats wet at critical times.
- Silt in the river bed is likely to be flushed out by more frequent flow events. This would increase the opportunities for egg-laying by fish spawning on gravel
- Natural wetting of river channels flood plains, temporary streams and billabongs could maintain habitat for feeding and resting.
- Wetting low-lying floodplain wetlands more frequently means that the exchange of fish between these wetlands and the river is likely to occur more often.
- That floods will stimulate recruitment by native species.
Fish were sampled by electrofishing from a boat. This technique temporarily stuns the fish so they can be caught and later released. Captured fish were identified, examined for disease, damage or abnormalities and measured. Fish observed but not caught and which could be readily identified were also recorded. Sixty river sites were sampled during the 1999-2000 summer. Ten of these were also sampled during the NSW Rivers Survey between 1994 and 1999. A total of 6280 fish was recorded during 1999/2000, of which 80% were native and 20% non-native fish.
In the inland rivers, the native fish caught were mostly Australian smelt and bony herring, with medium numbers of golden perch and Murray cod. Only small numbers of the threatened species, silver perch and trout cod, were caught. In the Hunter River the most abundant fish were striped mullet and freshwater herring. The non-native fish caught were mostly carp, gambusia and goldfish. The riverine sites will be sampled again during 2000-01 summer period as part of the ongoing monitoring program.
A total of 2284 fish were recorded during the three wetland sampling runs. Of these, 26% were native and 74% alien fish. Seven native species were recorded from the ten wetlands with number of species per wetland ranging from 1 to 7. Three alien fish species (carp, goldfish and gambusia) were recorded at 8 wetland sites and two species were recorded at the remaining two wetland sites.