Movements are essential for native Australian fishes, with their remarkable diversity of migratory strategies - involving upstream and downstream movements by adults and juveniles, and also in response to changing water levels and water quality. More than 44% of listed barriers to migration in NSW are <3m height, but there are many more small and unregistered barriers. Pipe fishways are a novel cost-effective solution that can be retrofitted over these ubiquitous small dams and weirs (Martino et al. 2025).
Our initial experiments demonstrated juvenile (<75 mm length) golden perch, silver perch, Australian bass, barramundi, and the freshwater catfish volitionally negotiated hypobaric pressure gradient in a 3 m-high inclined pipe emulating a siphon. We then tested a complete electric siphon fishway with two 24-volt ball-valves that open and close alternately, to moderate flow velocity to ranges that fish can swim against (~0.25 m/s). Laboratory tests of this siphon fishway showed that silver perch and barramundi ascended 2.4 m into the upstream tank, with notably improved efficacy for silver perch following repeat trials. A 5-day deployment under Audley weir in December 2025 was a successful operational trial but impacted by considerable tidal variation. Other locations are planned for this summer; and test a new fish-counting camera system; and to test various methods for fish attraction into a pipe.