What are the relative risks of mortality and injury for fish during downstream passage at hydroelectric dams in temperate regions? A systematic review

Abstract

Background: Fish injury and mortality resulting from entrainment and/or impingement during downstream passage over/through hydropower infrastructure has the potential to cause negative effects on fish populations. The primary goal of this systematic review was to address two research questions: (1) What are the consequences of hydroelectric dam fish entrainment and impingement on freshwater fish productivity in temperate regions?; (2) To what extent do various factors like site type, intervention type, and life history characteristics influence the consequences of fish entrainment and impingement? Methods: The review was conducted using guidelines provided by the Collaboration for Environmental Evidence and examined commercially published and grey literature. All articles found using a systematic search were screened using a priori eligibility criteria at two stages (title and abstract, and full-text, respectively), with consistency checks being performed at each stage. The validity of studies was appraised and data were extracted using tools explicitly designed for this review. A narrative synthesis encompassed all relevant studies and a quantitative synthesis (metaanalysis) was conducted where appropriate. Review findings: A total of 264 studies from 87 articles were included for critical appraisal and narrative synthesis. Studies were primarily conducted in the United States (93%) on genera in the Salmonidae family (86%). The evidence base did not allow for an evaluation of the consequences of entrainment/impingement on fish productivity per se; therefore, we evaluated the risk of freshwater fish injury and mortality owing to downstream passage through common hydropower infrastructure. Our quantitative synthesis suggested an overall increased risk of injury and immediate mortality from passage through/over hydropower infrastructure. Injury and immediate mortality risk varied among infrastructure types. Bypasses resulted in decreased injury risk relative to controls, whereas turbines and spillways were associated with the highest injury risks relative to controls. Within turbine studies, those conducted in a lab setting were associated with higher injury risk than field-based studies, and studies with longer assessment time

Stranded Kokanee Salvaged from Turbine Intake Infrastructure Are at Low Risk for Reentrainment: A Telemetry Study in a Hydropower Facility Forebay

“…Although fish entering the intake towers are avoiding the turbines and thus the associated direct mortality attributed to turbine passage (Pracheil et al 2016; Algera et al 2020), stranding in the surge towers is also potentially hazardous. Anecdotally, during the study dead fish (of various species including Rainbow Trout and Lake Whitefish) were observed and a considerable number of free‐swimming fish had fungal infections (see the Supplementary Material).…”

“…There are multiple downstream passage routes for fish at hydropower facilities, including turbines, spillways, and a variety of bypasses (OTA 1995; Katopodis and Williams 2012;). In facilities lacking passage infrastructure, fish passage through turbines is common and can result in mortality and/or injury (Coutant and Whitney 2000; Pracheil et al 2016; Algera et al 2020). Turbine intake towers, designed to retain water for safety and maintenance purposes, provide no purpose‐built fish passage (aside from being flushed through turbines) and can strand entrained fish for considerable periods of time.…”

“…Turbine intake towers, designed to retain water for safety and maintenance purposes, provide no purpose‐built fish passage (aside from being flushed through turbines) and can strand entrained fish for considerable periods of time. Fish entering and remaining in the intake towers via the surge tower avoid turbine passage, which is one of the most hazardous fish passage routes in terms of mortality and injury (Algera et al 2020). However, it is unknown if fish can navigate out of the intake towers and return to the reservoir.…”

Hydropower Development and the Loss of Fisheries in the Mekong River Basin

“…Downstream movement is impaired because drifting larvae, and even adult fish, are unable to find their way through the standing water of the impoundment to locate the outlet (Pelicice et al, 2015). Moreover, adult and juvenile fish which attempt to pass through hydropower infrastructure experience severe mortality from shear forces, physical strikes from turbine blades, and barotrauma or changes in barometric pressure (Algera et al, 2020).…”

Conservation behaviour in action: using fish behaviour to understand and mitigate the impacts of hydropower development

“…There are multiple downstream passage routes for fish at hydropower facilities including turbines, spillways, and a variety of bypasses (OTA 1995;Katopodis and Williams 2012). In facilities lacking passage infrastructure, fish passage through turbines is common and can result in mortality and/or injury (Coutant and Whitney 2000;Pracheil et al 2016;Algera et al 2020). Turbine intake towers, designed to retain water for safety and maintenance purposes, provide no purpose-built fish passage (aside from being flushed through turbines) and can strand entrained fish for considerable periods of time.…”