Laboratory testing of an innovative tube fishway concept

Abstract

Effective fishways are required for restoring fish migrations and reversing worldwide declines in freshwater fish while making sustainable use of water resources. Mitigation of barrier effects at high-head dams and weirs is often impeded by poor fishway performance and high costs. Improved and less-costly designs are urgently needed. Our innovative tube fishway concept combines established fishways techniques with aquaculture’s pumping methods and fish-behaviour insights for safe upstream fish passage. We experimented with scaled-down fishway designs using juvenile Australian bass (Percalates novemaculeata). An experimental horizontal-cylinder design successfully combined volitional-passage functions of existing fishways with non-volitional transfer using pumped water. Three key principles of fish behaviour in fishways led to design improvements: disturbed fish often seek refuge at depth; fishes’ escape reactions strongly motivate swimming into flows; and curved structures can reduce delays. In nine trials of the best fishway design, 44 of 45 Australian bass passed within 50 min. cycles. The tube fishway concept offers potential for effective upstream fish passage at new and existing barriers >∼2 m high, with low construction and operation costs and capacity to operate in variable flow regimes. Further development is proceeding with larger-scale laboratory trials, an innovative pumping system and more species.