Response of Eurasian otters (Lutra lutra) to underwater acoustic harassment device sounds

Emilie Nicoline Stepien*, Anders Galatius, Kirstin Anderson Hansen, Jacob Nabe-Nielsen, Jonas Teilmann, Magnus Wahlberg

*Corresponding author for this work

Research output: Contribution to journalJournal articleResearchpeer-review

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Abstract

Seal scarers (or acoustic harassment devices, AHDs) are designed to deter seals from fishing gear and aquaculture operations, as well as to prevent seals from entering rivers to avoid predation on valuable fish. Our study investigated the potential effects of AHDs on non-target species, specifically the Eurasian otters (Lutra lutra), by testing the reaction of two rehabilitated otters to simulated AHDs sounds at 1 and 14 kHz, with a received sound intensity of 105–145 dB re 1 µPa rms. The 1 kHz sounds were used to investigate alternative frequencies for scaring seals without scaring otters. The otters reacted to both 1 and 14 kHz tonal signals when retrieving fish from a feeding station 0.8 m below the surface. Their diving behaviour and time to extract food progressively increased as sound intensity increased for all tested sound levels. Notably, the sound levels used in our tests were significantly lower (40–80 dB) than the source levels from commercial AHDs. These findings highlight the importance of caution when using AHDs in river and sea habitats inhabited by otters, as AHDs can change their behaviour and potentially result in habitat exclusion.

Original languageEnglish
Article number4988
JournalScientific Reports
Volume14
Issue number1
Number of pages11
ISSN2045-2322
DOIs
Publication statusPublished - Dec 2024

Keywords

  • AHD
  • Behavioural response
  • Feeding disruption
  • Fish farm
  • Fishery
  • Habitat exclusion
  • Seal scarer

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