Fish need to be able to move freely among habitats to successfully complete all stages of their life-history. Fish move upstream and downstream (often up to many hundreds of kilometres), as well as into and out of connected wetlands and floodplains. Fish undertake these movements for various reasons including spawning, feeding and dispersal.

Connectivity of waterways is a key characteristic of a healthy aquatic ecosystem as it enables fish movements to be unrestricted. Aquatic habitats and waterways have been modified by the construction of dams, weirs and culverts to provide hydropower, irrigation and navigation. This provides important community benefits, but it has also changed how rivers flow, altered water quality, and reduced river connectivity.  These changes have led to reductions in population sizes and distribution of many fish species. To help alleviate some of these impacts there are a number of solutions that can improve river connectivity.

ARI has a long history in creating ways for fish to move past barriers, including the design of structures known as fishways. Fishways are complex to design and install, and vary from multiple rows of rocks, to series of connected concrete chambers. Designs are based on the ability of fish to swim and manoeuvre against a current, which varies depending on size and species. Numerous attributes contribute to the design of a fishway including water velocity, turbulence and light levels, and they can vary in success due to factors such as the size of fish using them. For example, fishways are often effective for large individuals, but it is more challenging for fish less than 40 mm in length to pass upstream. ARI works closely with Catchment Management Authorities, water authorities and the community to reconnect rivers across Victoria with the aim of helping to improve native fish populations.

A vertical slot fishway, made up of a series of concrete chambers

A rock ramp fishway on the Tarwin River near Leongatha

For more information contact: justin.o'connor@delwp.vic.gov.au or matthew.jones@delwp.vic.gov.au

The report below provides a framework for developing site-specific guidelines for fishways, while the journal article details how tracking fish movement provided insights into fish passage requirements:

ARI has been involved in other projects regarding fish passage: