Abstract
This report provides details of environmental monitoring activity at the Shetland Tidal Array from July 2024 to June 2025. It is the latest in a series of reports produced by Nova since monitoring of the operational tidal stream array in Bluemull Sound started in 2016.
The data analysed in this report gathered from turbine-mounted cameras between July 2024 and June 2025 continues to show that the likelihood of collisions between mobile species and turbines in the Shetland Tidal Array is extremely low. Analysis focused on diving birds and marine mammals, as the receptors of greatest nature conservation importance and those at the core of the objectives of the environmental monitoring.
Fish were not included in the analysis within this report. Previous monitoring reports have extensively documented fish presence and occupancy patterns around the turbines. Prioritising the analysis for diving birds and mammals enabled a greater proportion of the full dataset to be analysed (100%) than has been possible in previous reporting years.
No collisions or near misses were observed between diving birds and wildlife and turbines (either when operating or not operating) in any of the footage analysed, comprising fourteen thousand, nine hundred and ninety-eight (14,998) files.
An individual harbour seal (Phoca vitulina) was observed three times in one video file captured from the camera on T5 on 06/02/2025. The animal was observed surfacing past the turbine nacelle, then diving past the camera towards the seabed, before resurfacing again. The turbine blades were stationary and the tidal state based on Nova’s hydrodynamic model for Bluemull Sound was decreasing ebb/low water slack. Possibly the same animal was potentially seen 10 minutes earlier (10:14) on the camera mounted to T6, where an object which may have been a diving seal was seen some distance to the north of the turbine. Again, the turbine blades were stationary, as the tidal state was decreasing ebb, approaching low water slack.
No diving birds were observed in any of the footage.
This report also examines the proportion of good quality data acquired from subsea cameras that has been analysed over the lifetime of the Shetland Tidal Array monitoring programme (i.e. excluding footage in which biofouling compromises the ability to detect nearfield animal interactions). This exercise follows on from a systematic review of historic biofouling on turbine-mounted cameras from 2015 through to 20243. The recalculation of previous data analysis determined that 62% of the good quality footage has been analysed up to and including the current reporting period. Previous estimates that between 20% and 25% of the full dataset have been analysed were therefore a gross underestimate. This further highlights the rarity of nearfield encounters between animals and turbines and the extremely low probability of collisions.
This report further contributes to the growing evidence base that the risk of collisions between marine wildlife and tidal turbines is very low (probably close to zero).