Fish passage assessment in stepped fishways: Passage success and transit time as standardized metrics

Abstract Fishways are used worldwide to restore fish migration routes. However, there are few standardized metrics that allow the comparison of their performance in a consistence manner. This paper aims to assess fishway internal passage using two standardized metrics: passage success and transit time. Data from selected 20 field stepped fishways evaluation were gathered from a systematic review and own field experiments, considering potamodromous species as target fish. The influence of main biological and hydraulic parameters on these metrics was analyzed and modeled by logistic regression and survival analysis techniques. Passage success and transit time described reliably fishway performance. Both metrics were significantly influenced by fishway type, volumetric power dissipation, height drop between pools, slope, obstacle height, pool depth, species and fork length in fishway passage. This work may serve as a guide for all engineers and managers working in fishway assessment, design and management to assess and compare other fishways, select proper design parameters and open the discussion and future research on these topics.