Lake Pamamaroo Inlet Regulator - Temporary fishway
Introduction
The Menindee Lakes are a mosaic of highly productive natural water bodies that fill and dry with the flow of the Baaka to sustain life. In the 1960s, the lakes were regulated to support human needs, but Country, communities, culture and native fish, like Golden Perch, still depend on the lakes to survive.
When rains in the northern catchments bring fresh flows to the Baaka the river booms and the fish follow the flow. Adult Golden Perch move hundreds of kilometres upstream to find birthing places. Once the adults spawning movements end, the Golden Perch larvae drift downstream by the Baaka’s flow, where they settle into the Menindee Lakes nursery.
The lakes provide ideal habitat and food for fish to grow, improve their condition and be ready for further movement opportunities on warmer waters. The Menindee Lakes nursery is so productive that these Golden Perch can grow much quicker than their river-cousins. When flows begin to connect the lakes again, the fish follow its path and return to the main-stem Baaka to continue their cycle of life and disperse across the Murray-Darling Basin.
Fishway design
Natural flows experienced in the Northern Basin during 2025 provided optimal conditions for fish movement opportunities along the Baaka and between the Menindee Lakes system. The main issue in taking advantage of these conditions is that flows entering the Menindee Lakes need to have near equal lake levels upstream and downstream of the regulators to provide suitable flow velocities that provide opportunities for upstream passage.
These conditions are generally not met until later in the flow event, which results in many fish accumulating downstream of the regulators, making them susceptible to birds and fishers. Providing opportunities to move through the regulators helps reduce this risk whilst allowing the native fish to complete their natural life cycle.
To help maximise potential fish and flow outcomes, a temporary two-slot fishway solution has been designed in consultation with Jacobs Consulting for placement in the Lake Pamamaroo Inlet Regulator gates. The simple design creates low velocity areas that enable fish to approach the gates and pass upstream through the slots, which cater for different size classes of fish and a range of species.
Fishway modelling undertaken by Jacobs has shown that the baffles provide opportunity for fish passage over a difference of up to 650mm between upstream to downstream lake levels, with a difference of around 390mm providing optimal conditions.
DPIRD Fisheries trapping the temporary fishway, September 2025
NSW Department of Primary Industries and Regional Development (DPIRD) Fisheries have been working closely with partner agencies at WaterNSW, NSW DCCEEW Water and the Murray-Darling Basin Authority (MDBA) to allow for temporary fish passage between Lake Pamamaroo and Lake Wetherell using the temporary vertical slot baffles.
The baffles were installed on 15 September 2025 at the Lake Pamamaroo inlet regulator, when the difference between the lakes were within operational range of the fishway. NSW DPIRD Fisheries and NSW DCCEEW staff were onsite to conduct monitoring of fish passage the week of 15 September 2025, with four 3-hour trapping events undertaken.
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