A concept for improving Atlantic salmon Salmo salar smolt migration past hydro power intakes

Abstract

In this study, cost effective (in terms of reducing loss of power production) measures for increasing bypass migration of Atlantic salmon Salmo salar were developed and tested by establishing statistical models for timing of smolt migration and favourable diversion of water to the bypass. Initial tracking of radio-tagged smolts showed very low bypass migration under normal hydropower operations. Bypass migration increased when bypass discharge was experimentally increased and a model was developed that described relationships between total river discharge, bypass diversion and smolt migration route. Further improvements were obtained by installing two strobe lights at the power-production tunnel entrance that increased bypass migration during the night, but not during daytime. According to the behaviour of radio-tagged fish, the implemented measures contributed to increasing the annual percentage of bypass migration from 11 to 64%, and according to model predictions to 60-74% when the hydropower facilities were operated according to the developed models. To ensure correct timing of discharge diversion a smolt migration model was developed based on environmental variables that could successfully predict the general pattern of migration timing. The concept presented for improving smolt migration past hydropower intakes should be applicable in many systems where migration past hydropower installations cannot easily be solved by screening systems.

The future of fish passage science, engineering, and practice

“…Increased discharge over spillways or through special surface bypasses can provide safe routes for downstream migrating salmon (Adams, Plumb, Perry, & Rondorf, ; Fjeldstad et al., ). Redesigning traditional spillways or parts of them from vertical to angled orientations may offer improved downstream passage of European eel and possibly other fish species (Silva, Katopodis, Tachie, Santos, & Ferreira, ).…”

Modelling Tools to Analyze and Assess the Ecological Impact of Hydropower Dams

“…Ecological models can support decision making in environmental and conservation management [16] and have already been applied to assess the impact of dams on fish [17][18][19][20][21][22], macroinvertebrates [23][24][25], amphibians [26] and vegetation [27][28][29]. Models are being increasingly used in environmental assessment, planning and management [30].…”

Economic and policy considerations regarding hydropower and migratory fish

“…Where screening systems are not a viable option, downstream migration efficiency can be improved by increasing bypass discharge (Aarestrup and Koed ; Fjeldstad et al . ) and installing strobe lights at the entrance (Fjeldstad et al . ), although some studies suggest that guidance with light, noise or electricity may be inefficient (Larinier ).…”