Marine Mammals and Tidal Energy: Annual Report to Scottish Government

Palmer, L.; Gillespie, D.; Macaulay, J.; Onoufriou, J.; Sparling, C.; Thomson, D.; Hastie, G. (2019). Marine Mammals and Tidal Energy: Annual Report to Scottish Government (Report No. MMSS/002/15). Report by SMRU Consulting. Report for Scottish Government.

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Abstract

The work presented under the Marine Renewable Energy (MRE) theme falls in to three tasks;

MRE 1.1 – Fine scale marine mammal behaviour around tidal energy devices.
MRE 1.2 – Harbour seal movement modelling.
MRE 1.3 – Estimating collision risk using available information.

This annual report only considers MRE 1.1 as MRE 1.2 and 1.3 have been completed and are available here: http://www.smru.st-andrews.ac.uk/reports/.

MRE 1.1

This task aims to monitor the behaviour of marine mammals in the vicinity of an operational tidal turbine. A monitoring system utilising a combination of Passive Acoustic Monitoring (PAM), Active Acoustic Monitoring (AAM) and video cameras was deployed on a MeyGen turbine in the Pentland Firth to identify marine mammal species using the areas around the turbine and to construct 3D tracks of their movements.
After initial deployment on 24th October 2016, power to the turbine did not become available until 18th October 2017 when initial communications tests established that the PAM system was fully functional. However, no communications could be established with the video cameras or the Gemini multibeam sonars.
The sonar platform was recovered by SIMEC Atlantis Energy on 23rd July 2018 during planned operations to recover two other turbines. Subsequent inspection and fault diagnosis was undertaken by SMRU personnel at Nigg Energy Park on 7th August 2018. A number of possible failure points were identified including minor damage to the umbilical cable from the TSS, severe corrosion of the Hydrobond connectors used to attach the umbilical cable to the junction box, and water ingress in the junction box.
Since commissioning in October 2017, the PAM system has been operating stably for 95.3% of the time. The turbine was removed for maintenance from 22nd September 2018 to 18th December 2018, with PAM data collection resuming on the 19th December 2018.
The PAM system remains operational with routine checks and data archiving continuing. As agreed in the Steering Group meeting on 19th September 2018, monthly reporting was discontinued following the September 2018 report. Data collected following 31st January 2019 will not be manually processed for detections.
From the start of data collection up to the end of 31st January 2019 (~ 13 months monitoring), a total of 27 dolphin and 571 harbour porpoise encounters (≥ 30 clicks) were made. This equates to a mean of 1.6 (SD = 1.0) porpoise encounters and 0.1 (SD = 0.2) dolphin encounters per day.
A key output from the PAM data analyses will be the 3D locations of echolocation clicks in relation to the position and operational status of the turbine. Field trials to calibrate 3D localisation algorithms were conducted on 6th August 2018. This involved pinging the PAM array with a sound source from a vessel at known locations and depths. Data collected in these trials have been useful with the ongoing refinement of the PAMGuard localisation algorithms.
24 harbour seals had previously been tagged in the Inner Sound to quantify the movements of seals in a wider spatial context. A further 16 harbour seals were tagged between 16th and 24th April 2018. Of these, 12 transmitted location data and 12 transmitted high resolution dive data.
Of the tags deployed in 2018, 504 days of data were collected which included 53,484 GPS locations. Tagged seals spent ~12% of their time within the Inner Sound and ~0.001% within the MeyGen lease area. A total of 3 GPS locations were recorded within 50m of a turbine and the closest GPS location was 37m from a turbine.