Key words: fish migration, mesoscale movement, Murray-Darling Basin, Native Fish Strategy
Understanding the scale and movement requirements of fishes is important for their sustainable management. Information is available on the larger scale movement of adults of larger species in the Murray-Darling Basin (MDB), however prior to this project little was known about the movement of smaller or rarer species or early life history stages of larger species.
Broad aim and specific objectives: This project aimed to investigate mesoscale movement (movement beyond a single river meander or pool riffle sequence, or the movement between the river channel and its floodplain) for MDB fish species and/or life history stages for which there is little existing information. This included an investigation into both longitudinal (up and down the river) and lateral (across the river and floodplain) movements and possible movement triggers.
Methods: Lab-based tag retention trials were conducted to test the efficacy of Visual Implant Elastomer (VIE) tags and Passive Integrated Transponder (PIT) tags in a range of native fish species prior to field application. Field-based sampling took place both during regular and flood conditions, using a combination of conventional tagging, radio-telemetry and standard electrofishing and fyke netting techniques to study the movement of a range of northern MDB fish species. A mark-recapture study was undertaken to determine the movements of known individual fish or (in the case of smaller species or life stages) known batches. Quantitative or semi-quantitative sampling of fish numbers took place at regular intervals over a range of habitats to follow movements of fish populations. Data on environmental parameters that may trigger fish movements were recorded both using data collected by other agencies and project data loggers. Radiotelemetry data of Bony Herring (Nematalosa erebi) and Spangled Perch (Leiopotherapon unicolor) were also used to provide additional information on movements.
Findings: During the study, type of flow (natural or artificial), moon phase and time of year were found to be associated with movements of fish species. Carp Gudgeons (Hypseleotris spp.), Bony Herring, Spangled Perch and Golden Perch (Macquaria ambigua) sub-adults and juveniles were more mobile on natural flows than on flow releases from dams. This indicates that migration of these species may be stimulated by odours in run-off from floodplains. On falling flows there was a tendency for downstream migration by Carp Gudgeons, Bony Herring, and Spangled Perch of all sizes, Golden Perch sub-adults and juveniles, Dwarf Flathead Gudgeon (Philypnodon macrostomus) and juvenile Hyrtl’s Tandan (Neosilurus hyrtlii). This may be to avoid desiccation. Only a small proportion of the Murray-Darling Rainbowfish (Melanotaenia fluviatilis) population appeared to move. Of those that did, most moved upstream. In contrast to other species, Murray-Darling Rainbowfish were most mobile during artificial flow releases. They may prefer clearer water for movements associated with courtship displays and breeding.
In most species of fish, adults had more of a tendency to move upstream and juveniles downstream. This trend was very strong in Hyrtl’s Tandan. Most native species displayed diminished movement behaviour during the winter period, corresponding to periods of lowest flow in the northern MDB. Peak movement occurred in spring for Carp Gudgeons, Spangled Perch, Hyrtl’s Tandan, Olive Perchlet (Ambassis agassizii) and Murray-Darling Rainbowfish. These movements are believed to be associated with their reproductive strategy as many fish collected at this time were reproductively ripe.
Peak movements of juvenile and sub-adult Golden Perch and Bony Herring occurred during autumn. In the northern MDB, such behaviour would be a useful adaptation to enable dispersal to refuges prior to the onset of the winter and early spring dry season.
Carp Gudgeon were recorded moving up to 13 km upstream and more than 5 km downstream. Evidence suggests that Spangled Perch, Bony Herring, Dwarf Flathead Gudgeon, juvenile and sub-adult Golden Perch also make upstream movements in excess of 10 km. Downstream movements up to 2 km were recorded for Spangled Perch and up to 5 km for Bony Herring. Downstream movements of hundreds of metres were recorded for juvenile and sub-adult Golden Perch and Hyrtl’s Tandan.
Lessons learned and future directions: It is very important that managers consider the upstream and downstream movement of small fish when prioritising fish passage investment. In particular, the downstream movement for many species dictates that future fishway design should accommodate small-bodied fish as well as the premier native sport fish and other large-bodied species.
There is a need for improved coordination by fisheries managers and water managers on different methods of delivering water to increase lateral connectivity. The potential benefit of delivering water from dams less frequently or more strategically, and in larger volumes to replicate natural flows, needs to be understood by fisheries and water managers. Increased flow delivery may be achieved by combining environmental flow releases with natural flow events or irrigation releases.
Lateral habitats (e.g. lagoons) may be important for reproduction and long-term survival of some fish species and connectivity to and from the main channel should be an important consideration when determining flow releases.
Stakeholders and Funding bodies: This project was funded through the Murray-Darling Basin Authority’s Native Fish Strategy.
Contacts: Dr Michael Hutchison, Queensland Department of Agriculture Fisheries and Forestry. Tel: + 61 7 3400 2037, Email: Michael.Hutchison@daff.qld.gov.au