Summary

Fishways are commonly constructed on dams and weirs to assist the upstream migrations of freshwater fish. In Australia, a total of 76 fishways were constructed between 1912 and 1985. Unfortunately, most of these structures were based on designs for trout and salmon, and provided little, if any, passage for native fish. It could be possible to remodel or modify existing fishways to enhance fish passage by replacing them with more appropriate fishway designs. However, prior to this study, no such works have ever been attempted in Australia.

A fishway was constructed at Euston Weir on the Murray River in 1937. The fishway was among the first of its kind in Australia, but subsequent assessments have identified that it is largely unsuitable for Australian fish due to high flows and turbulence. To determine if the fishway could be rehabilitated, an 8-m long experimental fishway was installed within the existing channel. The new fishway was trialed trialled at three different slopes [8.3% (1:12), 14.3% (1:7) and 20% (1:5)] to examine its potential to improve fish passage at the site.

The improved configuration passed substantially greater numbers and size classes of fish than the original design. Fish between 45 and 630 mm ascended the fishway and manipulating the design parameters such as slope, length and width enabled the experimental fishway to pass a greater number of fish. In general, reducing fishway slope enabled the passage of more fish, which provided new information to aid the construction of future fishways in Australian systems.

This paper discusses and explores the application of this technology to new and existing fishways, to enhance migration pathways for a wide range of Australian fish.