Science Response 2012/005

Project to install underwater generators in the St. Lawrence River – Impact of turbines on fish passage

Context

A technology demonstration pilot project using underwater generators is currently under development in the St. Lawrence River near the port of Montreal at the Concorde Bridge. This project represents the first phase of a larger project that will include the installation of twenty underwater generators in Phase II, with an additional 200 underwater generators installed in the same area in subsequent phases. Fish Habitat Management Branch (FHMB) conducted an analysis of the monitoring program proposed by the proponent and, on January 17, 2012, requested the collaboration of scientists from the Regional Science Branch to provide advice on hydroacoustic monitoring techniques. The concerns of the FHMB deal primarily with the assessment of fish passage through the turbines, in particular the passive downstream migration of eels and larvae and the movement of fish in this area given their life cycle requirements. (e.g.: reproduction). This aspect of the monitoring program is considered a necessary component for evaluating the need to develop specific management measures to avoid or minimize fish mortality as a result of their passage in the area (e.g.: turbine stoppage during critical downstream migration periods). Given the short notice (advice required by February 17, 2012), a Science Special Response Process (SSRP) was introduced to provide scientific advice to FHMB.

This Science Response report stems from the analysis conducted between February 13 and 17, 2012 under the SSRP on the review of turbine impacts on fish passage as part of an underwater generator installation project in the St. Lawrence River by Fisheries and Oceans Canada, Canadian Science Advisory Secretariat. An underwater acoustics expert participated in the analysis.

The proposed monitoring plan for the project to install a collection of underwater generators in the St. Lawrence River requires special measures, in view of the environment in which the turbines will be installed. The physical environment throughout the study area will be undoubtedly very energetic, leading to high variability in both the spatial and temporal dynamics in the fish community. Spatial patchiness and temporal variability in movements will be important variables to consider. Multiple surveys must be performed, both before and after installation, to estimate this natural variability if one is to detect an effect of the turbine installation in fish densities, species composition and behaviour. Stationary, horizontal acoustic surveying is a well-tried approach for monitoring fish movements in riverine environments. However, one must be aware of the constraints and limitations of the method to ensure a successful deployment.

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