DOI: 10.5061/dryad.mpg4f4r2p
title: Reef effect of offshore structures on the occurrence and foraging activity of harbour porpoises

description: With increasing numbers of offshore structures to be decommissioned, a
 better understanding of their effect on marine predators is timely. There
 is some evidence that oil and gas platforms may attract marine mammals
 acting as artificial reefs. However, it is unclear whether different
 man-made structure designs have similar effects. Further, due to the lack
 of baseline data prior to installation, it is unknown whether artificial
 structures modify the diel patterns of occurrence and foraging behaviour
 of marine mammals. Here, we used passive acoustics to investigate the
 occurrence and foraging activity of harbour porpoises (Phocoena phocoena)
 around three artificial structures of different age and complexity. We
 deployed an array of echolocation click detectors (CPODs) in 2021, along a
 gradient of distances to these structures and assessed the extent to which
 porpoises were attracted to them. We also investigated the effect of these
 structures on the diel patterns of occurrence and foraging activity of
 porpoises. The probability of porpoise occurrence and foraging activity
 decreased with distance from offshore structures. A significant increase
 in porpoise occurrence and foraging was detected during night-time
 compared to daytime around all three offshore structures (&lt; 200 m).
 Comparing pre- and post-installation porpoise detections, the daily
 patterns of occurrence and foraging activity shifted from a weak diel
 pattern before the structure was installed, to a strong nocturnal pattern
 when the structure was present. These findings provide evidence that
 marine mammals are attracted to man-made structures and that porpoises
 modify their diel patterns of occurrence and foraging activity around
 them. This research suggests that offshore structures play an important
 role as foraging areas for marine mammals and provides key information for
 the decommissioning process.
description: Echolocation detectors (CPODs;
 Chelonia Ltd) were deployed in August 2021 to study the occurrence and
 foraging activity of harbour porpoises around three redundant artificial
 structures within Scottish shelf waters: Jacky Wellhead O&G
 platform, Beatrice Bravo O&G platform, and Beatrice Demonstrator
 turbines (offshore renewable energy).
description: Data consist of 20 files and include
 the datasets and R code required to repeat all the analyses. A full
 description of the files provided in the OFB_ReefEffect_Readme.txt
 file: 1.     
 OFB_ReefEffect_CPODexe_HP-Clickdetails_Aug2021.csv
 2.     
 OFB_ReefEffect_CPODexe_HP-DPH_perDAY_2021.txt 3.     
 OFB_ReefEffect_CPODexe_HP-PPM_perHOUR_2021.txt
 4.     
 OFB_ReefEffect_CPODexe_MaxClickInfo_perDAY_Aug21.csv 5.      OFB_ReefEffect_TPODexe_HP-ClickTimes_2005.csv 6.      OFB_ReefEffect_TPODexe_HP-PPM_perHOUR_2005.txt 7.      OFB_ReefEffect_HP-DPH-BPH_perDAY.csv 8.      OFB_ReefEffect_HP-DPH-BPH_perDAY_FinalDataset.csv 9.      OFB_ReefEffect_ HP-DPH-BPH_perDAYNIGHT_FinalDataset.csv 10.  OFB_ReefEffect_HP-PPM-BPM_perHOUR_2021.csv 11.  OFB_ReefEffect_HP-PPM-BPM_perHOUR_2005.csv 12.  OFB_ReefEffect_HP-PPM-BPM_Pre-Post-FinalDataset.csv 13.  OFB_ReefEffect_OffshoreStructures_Locations.csv 14.  OFB_ReefEffect_PAMLocations.csv 15.  OFB_ReefEffect - Buzz extraction and summarise perHour and perDay.R 16.  OFB_ReefEffect - Create DPH-BPH perDay - Final dataset.R 17.  OFB_ReefEffect - Create DPH-BPH perDayNight - Final dataset.R 18.  OFB_ReefEffect - Create Pre-Post Structure dataset.R 19.  OFB_ReefEffect - GLM GAM Modeling.R 20.  OFB_ReefEffect - Manuscript Plots