DOI: 10.5061/dryad.34tmpg4hs
title: Balancing risks of injury and disturbance to marine mammals when pile driving at offshore windfarms

description: 1. Offshore windfarms require construction procedures that minimise
 impacts on protected marine mammals. Uncertainty over the efficacy of
 existing guidelines for mitigating near-field injury when pile-driving
 recently resulted in the development of alternative measures, which
 integrated the routine deployment of acoustic deterrent devices (ADD) into
 engineering installation procedures without prior monitoring by Marine
 Mammal Observers. 2. We conducted research around the installation of
 jacket foundations at the UK’s first deep-water offshore windfarm to
 address data gaps identified by regulators when consenting this new
 approach. Specifically, we aimed to a) measure the relationship between
 noise levels and hammer energy to inform assessments of near-field injury
 zones, b) assess the efficacy of ADDs to disperse harbour porpoises from
 these zones. 3. Distance from source had the biggest influence on received
 noise levels but, unexpectedly, received levels at any given distance were
 highest at low hammer energies. Modelling highlighted that this was
 because noise from pin pile installations was dominated by the strong
 negative relationship with pile penetration depth with only a weak
 positive relationship with hammer energy. 4. Acoustic detections of
 porpoises along a gradient of ADD exposure decreased in the 3-hours
 following a 15-minute ADD playback, with a 50% probability of response
 within 21.7 km. The minimum time to the first porpoise detection after
 playbacks was &gt; 2 hours for sites within 1 km of the playback. 5.
 Our data suggest that the current regulatory focus on maximum hammer
 energies needs review, and future assessments of noise exposure should
 also consider foundation type. Despite higher piling noise levels than
 predicted, responses to ADD playback suggest mitigation was sufficiently
 conservative. Conversely, strong responses of porpoises to ADDs resulted
 in far-field disturbance beyond that required to mitigate injury. We
 recommend that risks to marine mammals can be further minimised by: 1)
 optimising ADD source signals and/or deployment schedules to minimise
 broad-scale disturbance; 2) minimising initial hammer energies when
 received noise levels were highest; 3) extending the initial phase of soft
 start with minimum hammer energies and low blow rates.Minhyuk Seo
description: Piling noise and Acoustic Deterrent device signals were measured
 using calibrated broadband noise recorders (Soundtrap ST300HF, Ocean
 Instruments) moored 2 m above the seabed. An array of moored echolocation detectors (V.0 and V.1 CPODs (www.chelonia.co.uk)) was used to assess variation in harbour porpoise detections in relation to experimental ADD exposure.   Data on the timing of piling operations, pile-hammer energies used, and pile penetration depths were provided by the wind farm developer (Beatrice Offshore Wind Ltd).
description: Data
 consist of the following 16 files/file packages. A full description of data identifiers, R code and the data files required to repeat  each analysis is provided in the text file: Thompson_BOWL_cMMMP_Data_Packages_Readme.txt   Raw data for analyses of echolocation detections are available at: https://doi.org/10.5061/dryad.5qg30sd 1_Thompson_BOWL_cMMMP_noise_wav_files_data_2020-10-12.zip 2_Thompson_BOWL_cMMMP_piling_pulse_data_2020-10-12.txt 3_Thompson _BOWL_cMMMP_R_code_to_analyse_piling_noise_variation_2020-10-12.R 4_Thompson_BOWL_cMMMP_piling_times_data_2020-10-12.txt 5_Thompson_BOWL_cMMMP_ADD_wav_files_data_2020-10-12.zip 6_Thompson_BOWL_cMMMP_R_code_to_prepare_porpoise_response_data-2020-10-12.R 7_Thompson_BOWL_cMMMP_ADD_experiment_data_2020-10-12 8_Thompson_BOWL_cMMMP_Distances_between_ADD_tests_&_CPODs_data_2020-10-12.txt 9_Thompson_BOWL_cMMMP_CPOD_porpoise_ClickCounts_data_2020-10-12 10_Thompson_BOWL_cMMMP_R_code_to_analyse_porpoise_responses_to_ADD_2020-10-12.R 11_Thompson_BOWL_cMMMP_Porpoise_responses_to_ADD_experiments_data_2020-10-12.txt 12_Thompson_BOWL_cMMMP_R_code_to_prepare_porpoise_return_times_data_2020-10-12.R 13_Thompson_BOWL_cMMMP_CPOD_porpoise_ClickDetails_data_2020-10-12.zip 14_Thompson_BOWL_cMMMP_expt_return_times_CPOD_data_2020-10-12.txt 15_Thompson_BOWL_cMMMP_baseline_return_times_CPOD_data_2020-10-12.txt 16_Thompson_BOWL_cMMMP_R_code_to_analyse_porpoise_return_times_after_ADD_playbacks_2020-10-12.R