Abstract
Reversing worldwide declines in freshwater fish while making sustainable use of water resources will require effective and economical fishways to restore fish migrations. Mitigation of barrier effects at dams and weirs is too often impeded by poor fishway performance and high costs, so that many fish migrations continue to be obstructed. Improved and less-costly designs are urgently needed. Our innovative pump fishway concept combines fish-behaviour insights, proved fishways techniques and aquaculture’s pumping methods for safe upstream transport of living fish. We ran a series of experimental trials using several scale-model fishway designs with young, hatchery-bred fish. Our horizontal-cylinder design successfully combined volitional-passage functions of existing fishways with non-volitional transport in a conduit carrying pumped water. Several 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 aid passage by reducing delays. Replicated trials finally produced an average of 98% successful passage, within brief cycling periods. The pump fishway concept offers potential for effective upstream fish passage at new and existing sites >~2m high, with low construction and maintenance costs and highly adaptable operation in variable flow regimes. Development beyond the concept-trial phase is now a priority.