A trap-and-haul fishway for upstream transfers of migrating fish at a challenging dam site

Abstract

Abstract Australia’s first trap-and-haul fishway was built to overcome site-related and biological challenges of providing upstream fish transfer at a 62 m dam. Challenges included multiple barriers, major flow alterations, infrequent spillway flows, a reservoir distant from tailwater, differing migration strategies and the presence of undesirable fish species. Planning assessments concluded upstream fish transfer would create environmental and fisheries benefits, but providing for downstream passage, other than protecting fish emigrating during spillway flows, was not justified. The trap-and-haul fishway collected upstream-migrating fish for transfer to multiple release sites. It provided flexibility to accommodate diverse species, sizes, abundance and behaviour while operating at flows ≤1:20 Annual Exceedance Probability. The fishway facilitated operational monitoring and removal of invasive and non-indigenous species, with features to limit predation. A barrier weir guided fish and minimized bypassing in spilling flows. Over four years’ operation approximately 43,700 fish, representing all the river’s 23 large and small-bodied migrating species, were transferred. Fish belonging to three unwanted species were removed. Stable, restricted flow releases through the fishway inhibited attraction, causing fish aggregations and reduced performance. Opportunities for improvement are recommended. The system’s design, operations and results have shown potential value for application at comparable sites elsewhere.