PNNL

Abstract

American eel (Anguilla rostrata) populations have declined within their native range along the eastern coast of North America due to factors such as commercial fishing, habitat alteration, and dams. Efforts are underway to restore these populations. American eel are catadromous fish species, and high mortality rates (>40%) have been observed for the adult, freshwater life stage passing downstream through hydropower turbines. Lacerations and sectioning of fish have been observed downstream of turbines and these injuries are commonly associated with direct contact with the turbine runner, whether through blade strike or pinching and grinding. There is also potential that exposure to fluid shear may be a source of injury, however, little is known about American eel susceptibility to this physical stressor. Eels are considerably flexible when compared to other fish species, and lack other morphological characteristics that would make them susceptible to fluid shear, such as protruding eyes, large scales, and large operculum. European eel, which have previously been tested for susceptibility to fluid shear, were found to be resilient. To determine if American eel are also resilient to fluid shear, twenty yellow-phase American eel were exposed to a water jet, simulating severe fluid shear (strain rate > 800 s-1) that fish may experience when passing downstream through hydropower turbines. American eel showed no immediate or delayed (48 h) signs of injury after exposure to severe fluid shear. Based on this study, and a previous study conducted on American eel susceptibility to barotrauma, the source of injury and mortality of American eel passing through turbines is likely attributed to blade strike or pinching and grinding within moving parts of the structure.