Non‐salmonids in a salmonid fishway: what do 50 years of data tell us about past and future fish passage?

Salmonid fishways have been used in many countries for non‐salmonid fishes, including Australia, but generally with poor results. Trapping the entrance and exit of a 1:9 gradient salmonid fishway on the Murray River confirmed very poor passage of native fish, with <1% of the most abundant species ascending. Fifty years of fish passage monitoring showed the numbers of three native species declining by 95–100% and non‐native fish becoming dominant. Fishways are now being designed for native fish and being quantitatively assessed, but daily flow management also needs to be addressed. The ecological model for passage of potamodromous fishes has changed from passing adults of a few species to one that incorporates the whole fish community, specifically: immature fish of large‐bodied species that dominate numbers migrating upstream; a diverse range of movement strategies; and small‐bodied species, crustaceans and low numbers of less‐mobile species.