Guiding migrating salmonid smolts: Experimentally assessing the performance of angled and inclined screens with varying gap widths

The loss of longitudinal connectivity in regulated rivers, both up- and downstream, has been detrimental for biodiversity worldwide. While progress made regarding upstream fish passage solutions, many questions remain unanswered downstream alternatives. To address these knowledge gaps, we used Atlantic salmon (S. salar) smolts to experimentally assess the guidance efficiency rates produced by several common screen-and-bypass systems. Vertical screens with horizontally oriented bars extending across a turbine intake channel at shallow angle (angled screens), combined single, full-depth bypass entrance their end, were on average 20% more effective that 10 times higher than which extended perpendicularly vertically rose gradually towards surface (inclined screens) surface, either side screen. Among inclined screens, gap width was negatively associated efficiencies smallest (15 mm) exhibited 41% greater largest (30 mm). angled performance closely linked construction material as metal racks over three faster flexible Kevlar netting. Overall, through therefore into tentative area, positively twice prevalent among relative screens. Ultimately, an screen 30 mm highest (a 30% improvement next best screen), while lowest rates. These results have implications suitability solutions large- small-scale hydropower plants where are currently lacking or inadequate.