Alosines (shad and river herrings) are an important and highly sensitive group of migratory fish species affected by hydropower and river fragmentation in eastern North America. In September of 2021, Natel evaluated juvenile alewife (Alosa pseudoharengus, a type of river herring) passage survival through a 0.55 m (1.8 ft) Restoration Hydro Turbine (RHT) at Freedom Falls, Maine, with assistance from Kleinschmidt Associates.

We collected locally downstream migrating juveniles, passed them through the turbine in groups, and collected them at the outlet with a specialized trap. We captured turbine passage with high-speed video and compared turbine passage survival rates with control group survival. This work is summarized in our peer-reviewed paper "Juvenile Alewife Passage through a Compact Hydropower Turbine Designed for Fish Safety," published by North American Journal of Fisheries Management in 2023.

The combined immediate and 48-h survival rates for all treatments, corrected for control mortality, were 98.2 and 100.0 %, respectively. The passage of alewife through the runner region of the turbine was also captured with high-speed video. The results of the study demonstrate that the RHT is an effective way to pass juvenile alosines downstream at hydropower facilities.