Effectiveness of High-Velocity Inclined Profile-Bar Fish Screens Measured by Exclusion and Survival of Early Life Stages of Fathead Minnow

Abstract We estimated exclusion and survival rates of fathead minnow Pimephales promelas exposed to four configurations of a high-velocity inclined profile-bar screen. These screens are functionally different from conventional positive-barrier designs because fish behavior and swimming ability are not design considerations. We tested screens inclined at 45° or 60° that had 1.0-mm or 0.5-mm slot widths and used 5–45-mm total length fathead minnow released high or low in the water column. The exclusion rate for 45.0-mm and 22.5-mm fathead minnow was 100%. Survival of 45.0-mm fish was 88%; latent mortalities were attributable to nonscreen causes. Survival of 22.5-mm fish was 100%. Exclusion rates for high- and low-release 12.5-mm fathead minnow were nearly 100%. Survival rates for high-release 12.5-mm fathead minnow were 62– 86% and were similar to or higher than those for low-release fish (15–71%). Exclusion rates of 7.5-mm and 5.0-mm fathead minnow in tests with the 0.5-mm screen were 88–95% regardless of release position. Exclusion rates for 7.5-mm and 5.0-mm fish tested with 1.0-mm screens were mostly lower (2–90%), especially for low-release fish. Survival rates for 7.5-mm fathead minnow in high releases were 26–62%, but survival rates for low-release 7.5-mm fish (0–9%) and 5.0-mm fish (28%) were low. The screen angles we tested had little consistent effect on exclusion or survival rates. The successful exclusion and survival we documented for various life history stages of fathead minnow, coupled with the high hydraulic efficiency and self-cleaning properties of high-velocity inclined profile-bar fish screens, indicates that this is a potentially effective tool for managers seeking to reduce entrainment loss of fish in aquatic ecosystems.