Behavioral Response Study on Seismic Airgun and Vessel Exposures in Narwhals

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DOI

  • Mads Peter Heide-Jørgensen, Greenland Institute of Natural Resources
  • ,
  • Susanna B. Blackwell, Greeneridge Sciences Inc
  • ,
  • Outi M. Tervo, Greenland Institute of Natural Resources
  • ,
  • Adeline L. Samson, Universite Grenoble Alpes
  • ,
  • Eva Garde, Greenland Institute of Natural Resources
  • ,
  • Rikke G. Hansen, Greenland Institute of Natural Resources
  • ,
  • Manh Cu’ò’ng Ngô, Greenland Institute of Natural Resources
  • ,
  • Alexander S. Conrad, Greeneridge Sciences Inc
  • ,
  • Per Trinhammer
  • Hans C. Schmidt, Greenland Institute of Natural Resources
  • ,
  • Mikkel Holger S. Sinding, Trinity College Dublin
  • ,
  • Terrie M. Williams, University of California at Santa Cruz
  • ,
  • Susanne Ditlevsen, Københavns Universitet

One of the last pristine marine soundscapes, the Arctic, is exposed to increasing anthropogenic activities due to climate-induced decrease in sea ice coverage. In this study, we combined movement and behavioral data from animal-borne tags in a controlled sound exposure study to describe the reactions of narwhals, Monodon monoceros, to airgun pulses and ship noise. Sixteen narwhals were live captured and instrumented with satellite tags and Acousonde acoustic-behavioral recorders, and 11 of them were exposed to airgun pulses and vessel sounds. The sound exposure levels (SELs) of pulses from a small airgun (3.4 L) used in 2017 and a larger one (17.0 L) used in 2018 were measured using drifting recorders. The experiment was divided into trials with airgun and ship-noise exposure, intertrials with only ship-noise, and pre- and postexposure periods. Both trials and intertrials lasted ∼4 h on average per individual. Depending on the location of the whales, the number of separate exposures ranged between one and eight trials or intertrials. Received pulse SELs dropped below 130 dB re 1 μPa2 s by 2.5 km for the small airgun and 4–9 km for the larger airgun, and background noise levels were reached at distances of ∼3 and 8–10.5 km, respectively, for the small and big airguns. Avoidance reactions of the whales could be detected at distances >5 km in 2017 and >11 km in 2018 when in line of sight of the seismic vessel. Meanwhile, a ∼30% increase in horizontal travel speed could be detected up to 2 h before the seismic vessel was in line of sight. Applying line of sight as the criterion for exposure thus excludes some potential pre-response effects, and our estimates of effects must therefore be considered conservative. The whales reacted by changing their swimming speed and direction at distances between 5 and 24 km depending on topographical surroundings where the exposure occurred. The propensity of the whales to move towards the shore increased with increasing exposure (i.e., shorter distance to vessels) and was highest with the large airgun used in 2018, where the whales moved towards the shore at distances of 10–15 km. No long-term effects of the response study could be detected.

OriginalsprogEngelsk
Artikelnummer658173
TidsskriftFrontiers in Marine Science
Vol/bind8
ISSN2296-7745
DOI
StatusUdgivet - jun. 2021

Bibliografisk note

Funding Information:
We thank the hunters from Ittoqqortoormiit for their assistance in catching the whales and in deploying and collecting instruments; we are particularly indebted to Inuuta Scoresby Hammeken, who facilitated a major part of the field operations. The crews of r/v Paamiut and HDMS Lauge Koch are acknowledged for their skillful navigation in Scoresby Sound. Mikkel Skovrind, Jeppe M?hl, Mads Fage Christoffersen, Sixten H?llert, Solveig Heide-J?rgensen, Alice H?llert, and Beau Richter are thanked for their help with field logistics, camp maintenance, and capturing operations in Hj?rnedal. Lars Mejlgaard Rasmussen and Andreas Skifter Madsen, Aarhus University, are thanked for their assistance with seismic operations onboard r/v Paamiut and HDMS Lauge Koch. This study is part of the Northeast Greenland Environmental Study Program, which is a collaboration between DCE?Danish Centre for Environment and Energy at Aarhus University, the Greenland Institute of Natural Resources, and the Environmental Agency for Mineral Resource Activities of the Government of Greenland. Oil companies operating in Greenland are obliged to contribute to knowledge regarding environmental matters. Funding. The Mineral Licence and Safety Authority (MLSA) and Environmental Agency for Mineral Resource Activities (EAMRA) of Greenland provided funding as part of the Joint Northeast Greenland Strategic Environmental Study Program. Additional funding was obtained from the Carlsberg Foundation and the Danish Cooperation for the Environment in the Arctic (DANCEA). Permission for capturing, handling, and tagging of narwhals was provided by the Government of Greenland (Case ID 2010 ? 035453, document number 429 926). The project was reviewed and approved by the IACUC of the University of Copenhagen (June 17, 2015). Access and permits to use land facilities in Scoresby Sound were provided by the Government of Greenland. No protected species were sampled.

Publisher Copyright:
© Copyright © 2021 Heide-Jørgensen, Blackwell, Tervo, Samson, Garde, Hansen, Ngô, Conrad, Trinhammer, Schmidt, Sinding, Williams and Ditlevsen.

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