Fish passage remediation generally focusses on restoring connectivity on mainstem infrastructure as river channels are the primary migration pathway for native fish to spawn, disperse and access habitats. Critical off stream migration areas are often overlooked due to limited connection opportunity, although serve as crucial nursery habitat, providing recruitment hotspots by supporting rapid growth and boosting native fish populations.
The Menindee Lakes system is a series of interconnected ephemeral lakes in the Murray Darling Basin and the critical junction connecting the northern and southern basin. Lake Pamamaroo is a highly productive nursery habitat, particularly for Golden perch, located adjacent to the original Darling-Baaka River. Lake Pamamaroo is connected and allows inflows from the northern basin via a 15 steel radial gate weir. Fish passage success is governed by weir operations and suitable inflows and water quality.
This study looks at a how a temporary fishway retrofit in conjunction with weir operations has supported increased movement and dispersal of native fish between Lake Pamamaroo and the northern basin. A low-cost 2 slot baffle fishway was designed and installed in an end gate bay in the Lake Pamamaroo Inlet Regulator, with modelling of internal hydraulics indicating the opportunity for fish to pass head differentials of up to 650mm. Implementation and field validation of biological modelling showed passage rates up to 1344 Golden perch per day and passage success above the modelled conditions. Optimum passage efficiency was at a head differential of 300-400mm, particularly during specific Menindee Lake system operation scenarios.