Integrating Hydroacoustic Approaches to Predict Fish Interactions with In-stream Tidal Turbines

The effects of in-stream tidal energy turbines on fish are of high concern to regulators, project developers, fishers, and other members of the public. While we are building our understanding of fish use of high-flow tidal areas, there is still much to be understood in terms of the biology, biophysical linkages, and the methods we are developing to study them. In Nova Scotia, this uncertainty has led to added monitoring requirements at the FORCE tidal test site, but there are limited existing best practices for predicting or detecting in-stream tidal turbine effects on fish and no standard approaches to environmental monitoring.

FORCE has been monitoring fish presence and distribution at the test site in Minas Passage using two different hydroacoustic approaches. One is a vessel-based mobile survey, which utilizes a down-facing echosounder to sample fish densities across the test site area. The other is a platform-based, stationary survey, which deploys an echosounder on a bottom-mounted platform for long periods of time. Integrating these two approaches in this study, researchers sought to answer: 

  1. What is the spatial representative range of hydroacoustic data collected at one location in the FORCE test site?
  2. What is the temporal representative range of hydroacoustic data collected over a short period of time at the FORCE test site?
  3. Are concurrent results from the mobile and stationary datasets comparable to each other, and how did challenges differ across methods?

Answering these questions will allow for a better understanding of fish use of the site, which will inform probability of encounter models in future. The information gained through this integrated approach and evaluation of the strengths and weaknesses of each survey method will additionally inform recommendations of best practices for monitoring turbine effects.