Passage survival of European and American eels at Francis and propeller turbines

Abstract

We present the magnitude of losses of European eel Anguilla anguilla and American eel A. rostrata in passage through propeller and Francis turbines at hydroelectric projects. Survival and injury rates and types were turbine type related. Overall, eel survival was higher (mean ± 90% CI = 95.1 ± 5.3%,) and injury rate lower (12.5 ± 10.5) at Francis than propeller turbines (survival = 80.7 ± 6.4%; injury rate = 25.7 ± 7.9%). The common injury type at Francis turbines was bruises and at propeller turbines was severance. Blade shape and thickness of the leading edge of the blades (rounded, thick buckets of Francis turbines v. flatter, sharper edged blades in propeller turbines); eel entry routes into the turbines; their flexible, cylindrical body shape and orientation probably contributed to these differences. Relationship between survival and injury and turbine characteristics was turbine specific. For Francis turbines, one negative correlation (r = −0.986, P < 0.01) between survival and runner speed was found and two positive correlations between injury rates and fish length (r = 0.740, P < 0.10) and number of blades (r = 0.835, P < 0.05) were noted for propeller turbines. Several severely injured eels remained active 48 h after turbine passage suggesting caution is warranted when using telemetric movement for estimating eel survival. We conclude there is a need to (a) better understand travel paths and approach orientation of eels through turbines; (b) determine where only eel passage is of concern at hydropower plants that have both turbine types and therefore preferential operation of Francis turbines may be considered; (c) inform hydropower plant operators where turbine replacement is being considered and downstream eel passage is of concern that replacement by Francis or bulb turbines may prove beneficial for eel passage.

Deep Learning for Automated Detection and Identification of Migrating American Eel Anguilla rostrata from Imaging Sonar Data

“…The dramatic decline of these eel populations is attributed to several factors including the construction and operation of hydroelectric facilities, degradation and pollution of habitats, commercial harvest, and changes in ocean-atmospheric conditions affecting their marine life stages [7]. Hydroelectric facilities affect the species in at least two ways: (1) the dams impede upstream migration of juveniles [8], and (2) adult migrants are exposed to risk of injury and mortality when they pass downstream via hydroelectric turbines [9,10].…”

American eel resilience to simulated fluid shear associated with passage through hydroelectric turbines

“…American eel susceptibility to blade strike has been observed in laboratory testing, where mortality occurred in 35% of American eel when exposed to simulated turbine blade strike over various combinations of blade thicknesses, blade velocities, strike locations, and fish orientations (Saylor et al, 2019). Studies have linked turbine induced injuries and mortality in American eel to strike or pinching and grinding because the observed injuries included lacerations or complete sectioning of the fish (Heisey et al, 2019;Saylor et al, 2019). However, there is potential that injuries can also be caused by exposure to rapid decompression (e.g.…”

In Search of a Cost‐Effective Approach for Estimating Dam Passage Survival

“…Downstream-migrating fish may sustain injury or death while passing in-river structures such as hydroelectric dams and water diversion facilities. At U.S. Atlantic coast hydroelectric dams, migrant Shad Alosa sapidissima (Dadswell et al 2018;Mathur et al 2018)), Atlantic Salmon Salmo salar (Lawrence et al 2016;Nyqvist et al 2017), American Eels Anguilla rostrata (Eyler et al 2016;Heisey et al 2019) and Striped Bass Morone saxatilis (Dubois and Gloss 1993;Amaral et al 2015) among other species may experience mortality during passage. Similarly, a suite of salmonid species and Pacific Lamprey Entosphenus tridentatus can experience deleterious effects of passage at U.S. Pacific coast hydroelectric dams (Moser et al 2002;Skalski et al 2016;Quinn 2018).…”