Fishway - Cone

Cone fishways consist of a series of pre-fabricated (precast) cone shaped concrete baffles installed laterally within a concrete channel. These designs are similar to precast rock ramp fishways, but instead of having individual ridge elements precast off site, the whole ridge is formed as one piece.

Cone fishways are generally used on low weirs and, depending on the length of the fishway, resting pools are incorporated to allow fish to rest as they move upstream. Cone fishways are appropriate for remote sites where transport costs are high, and rock is unavailable for the construction of a natural rock ramp fishway.

The design for these fishways is suited for low head differential to pass both small and large fish sizes. The designs can include low flow and high flow baffles to cater for all species across differing flow ranges.

To date no cone fishways have been installed in NSW, however the upcoming refurbishment of Stroud Weir fishway from natural rock to a cone design will be the first.

Case study

Stroud Weir on the Karuah River, was identified as a priority for remediation because it was a significant barrier to fish moving both upstream and downstream. This site was remediated with a natural rock ramp fishway in 2007 and reopened approximately 34 km of upstream habitat, a significant improvement for fish access in the river.

In 2021 the fishway was reassessed where it was noted that due to some movement in rock within the fishway, the hydraulics within the fishway were likely limiting fish passage. To meet current contemporary design standards for rock ramp fishways it was agreed to upgrade the site with a prefabricated cone fishway components to address the functionality issues.

Further reading

• Cone Fishways Reach Significant Stage of Development (Australasian Fish Passage Services)