Fishways - novel designs

Eel and elver fishways

In addition to "standard" fishway designs and the novel designs mentioned below that cater to a range of fish species and size classes, elver passes have been developed to provide fish passage for eels in situations where other fishways are inappropriate. Elver passes generally comprise a small-diameter pipe or channel lined with materials such as coarse brushes that provide migrating juvenile eels with a damp, complex surface over which to wriggle and move upstream^1,2.

References

^{1 Mitchell (1990) and Clay (1995) in Thorncraft, G. and Harris, J. (2000). Fish Passage and Fishways in NSW a Status Report. Cooperative Research Centre for Freshwater Ecology Technical Report 1/2000.}

^{2 Jellyman et al (2017). The effect of ramp slope and surface type on the climbing success of shortfin eel (Anguilla australis) elvers. Marine and Freshwater Research.68: 1317–1324.}

Novel designs

As our understanding of fish passage requirements grow, so do the opportunities to develop and test new fishway designs.

Recently several new designs have been developed to overcome obstacles encountered during design and construction of traditional fishway types and to develop fish passage solutions at sites where construction is difficult.

Whilst innovation is encouraged, any new design needs to go through a rigorous design and modelling process before they get to construction stage.

Designing a novel fishway requires close consultation with DPIRD Fisheries and the process will generally include physical and computational fluid dynamic (CFD) modelling to ensure key design criteria are suitable for the swimming abilities and migration preferences of native fish and other river fauna.

Example novel fishway designs presented here are still going through the processes above and are yet to be formally adopted in the field to provide ongoing fish passage.

Jacobs and Fishway Consulting Services (JFCS) Fishway

The Jacobs and Fishway Consulting Services (JSCS) fishway is developing a new innovative fishway design that uses precast concrete baffle units within a concrete channel to simulate a pool and riffle profile.

This design provides for safe upstream and downstream fish passage and maximises the proportion of the river discharge through the fishway.

The design of the baffles incorporates a V-shaped configuration that facilitates the downstream passage of floating debris and reduces hydraulic conditions at the extremities of the baffle. Engineers and researchers are working together to finalise designs to for construction of the first of this design type.

Fishway - Fish Tube/Pump

Tube fishways work by pumping fish at high velocity through a tube running over the obstructing barrier to deliver fish safely on the upstream side. Fish passing through the tube are protected by the cushion of water and have potential to be a low cost and low energy installation.

Engineers and scientists have been working on numerous designs where an attraction chamber provides suitable attraction flow to guide fish into the system. Once fish are within the chamber a series of valves and pumps operate to push the fish from the downstream side of a barrier and elevate them to the upstream side. These designs have proven effective in northern hemisphere, however, they remain in a testing phase in NSW for local species. Watch the video below for more detail on technology being developed by the University of NSW and head to the Menindee Lower Darling-Baaka Temporary Tube Fishway Trial page to find out more on how this technology is being applied in the field.