MEPS prepress abstract  -  DOI:

First in-situ passive acoustic monitoring for marine mammals during operation of a tidal turbine in Ramsey Sound, Wales

Chloe E Malinka*, Douglas M Gillespie, Jamie DJ Macaulay, Ruth Joy, Carol E Sparling


ABSTRACT: The development of marine renewables has raised concerns regarding impacts on wildlife, and due to laws applying to many marine mammal species, environmental monitoring is often required. Here, we examine three months of continuous passive acoustic monitoring (PAM) data collected at Tidal Energy Ltd.’s DeltaStream turbine deployment, in Ramsey Sound, UK. This study aimed to: 1) assess the viability and performance of a PAM system at an operational turbine, 2) describe the 3D movements and behaviours of small cetaceans in the vicinity of the turbine, and 3) examine patterns in small cetacean presence at the site by modelling changes in detection rates against temporal and environmental variables. The PAM system, comprising 12 time-synced hydrophones arranged in four clusters, was designed to acoustically detect, classify and track porpoises and dolphins via their vocalisations within an ~100 m radius around the tidal turbine. A total of 247 small cetacean encounters were identified from click detections, which were also used to reconstruct the spatial movements of porpoises and dolphins, including close approaches to the turbine, even whilst it was emitting loud mechanical clanging sounds. Not all hydrophones were functional, and this, combined with high electrical noise levels, limited the ability to localise porpoise clicks, with the probability of being able to detect and localise a click reduced by 50% at a range of ~20 m. It is possible that mechanical clanging sounds on the turbine alerted marine mammals of its presence. GAM-GEE models examined patterns in porpoise acoustic detection, with tidal state, time of day, low frequency noise levels and moon phase best explaining the acoustic presence of porpoise. The limited duration of turbine operation meant that there was insufficient data to understand the effect of turbine rotation on animal presence and movement close to the turbine. This is the first description of how small cetaceans behave and move around a tidal turbine, and we present recommendations regarding how PAM can be used to improve environmental monitoring at future tidal energy sites.