Interaction uncertainties between tidal energy devices and marine animals have the potential to disrupt the tidal energy industry as it advances. Best-practices for environmental impact assessments (EIAs) must be explored that are able to provide conclusive recommendations for mitigating environmental impact concerns of tidal energy developments. As the tidal energy industry is moving closer to commercial-scale array installations, the development of standardised EIAs would allow for potential impact concerns for the marine environment to be identified and minimised early in the site-development process. In an effort to help formulate a standardised EIA framework that addresses knowledge gaps in fish-current interactions at tidal energy candidate sites, this study investigated changes in fish aggregations in response to tidal currents at a tidal energy candidate site in Australia prior to turbine installation. Here, we present the dataset collected for this study that includes tidal current information from Acoustic Doppler Current Profiler (ADCP) measurements, volume backscattering strength from a four-frequency biological echosounder (Acoustic Zooplankton and Fish Profiler – AZFP) as an indicator for fish biomass, and fish aggregation metrics calculated from volume backscatter in post-processing. ADCP and AZFP were installed on a bottom-mounted mooring and engaged in a concurrent sampling plan for ~2.5 months from December 2018 to February 2019. The mooring was deployed in the Banks Strait, a tidal energy candidate site located in the northeast of Tasmania, Australia, at a location favourable for tidal turbine installations considering current speed, depth, substrate, sediment type and proximity to shore. The ADCP dataset includes current velocity and direction measurements at a 1 m vertical and 1-sec time intervals. The raw AZFP dataset includes volume backscattering strength collected at 4-sec time intervals with a vertical resolution of 0.072 m in raw, and 0.1 m in pre-processed form. Fish aggregation metrics were derived in post-processing and are presented by the minute along with corresponding environmental conditions for current speed, shear, temperature, diel stage, and tidal stage compiled from both AZFP and ADCP datasets.
The dataset presented was collected as part of the field campaign of the Australian Tidal Energy (AUSTEn) project, a collaborative research project looking to assess the tidal energy potential of Australia and conduct site-specific characterisation studies of high-potential candidate sites.
This study applied hydroacoustics to investigate interactions between fish and hydrodynamic features (e.g. tidal currents). A bottom-mounted mooring was deployed that housed a biological echosounder in form of an Acoustic Zooplankton and Fish Profiler (AZFP) from ASL Environmental Sciences to measure volume backscattering strength over four frequencies (38-67-125-200 kHz), and a Nortek Signature 500 AD2CP to measure current speed and direction. AZFP and ADCP were setup in a concurrent sampling plan with the four AZFP transducers ~1 m above sea floor and the Signature 500 AD2CP ~1.5 m above the sea floor.
Several post-processing steps were implemented to mitigate changes in background noise due to current speed and wind stress, and isolate acoustic fish returns remaining scattering sources. Once isolated, volume backscatter measurements containing fish underwent further post-processing to determine fish aggregation metrics including density, abundance, centre of mass, dispersion, % water column occupied, evenness, and index for aggregation. Each aggregation metric was then binned by minute along with corresponding environmental conditions for current speed, shear, temperature, diel stage, and tidal stage. Detailed processing steps are presented in the accompanying manuscript publications (In press).