American eel, 2023

Study Overview
Scientific partner:
Natel only
American eel
Fish length:
100 to 271 mm (3.9 to 10.6 in)
RHT runner:
0.55 m (1.8 ft) diameter
9.37 m (31 ft)
Rotational speed:
980 rpm, 28.2 m/s
Turbine-passed fish:
Control fish:
100% immediate survival, 99.2% 48h survival

The goal of this test was to gather data on how higher tip speeds affect eels passing through an RHT. In this test, we spun the 0.55 m (1.8 ft) diameter test turbine at 980 rpm to produce a tip speed of 63.1 mph.

As established in tests conducted by Alden Lab, there is a direct relationship between the length of a fish that can survive a turbine blade strike and the thickness of the blade that struck the fish. When fish length is similar to blade thickness, fish are slowed (up to 30%), and their bodies conform to the blade shape, pushing them away from the leading edge before impact.

In this test, we used small (106 to 270 mm / 4.2 to 10.6 in) eels with our scale-model test turbine to match the fish length to blade thickness ratio that would be present at a full-scale hydropower site through which full-grown (400-800 mm / 15.7-31.5 in) eel were migrating downstream.