The influence of high-amplitude acoustic deterrents on the distribution, abundance, and behaviour of baleen whales

Nordeen, Carrie Louise (2002) The influence of high-amplitude acoustic deterrents on the distribution, abundance, and behaviour of baleen whales. Masters thesis, Memorial University of Newfoundland.

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Abstract

The influence of high-amplitude acoustic deterrents (HAADs) on mysticetes, including humpback whales (Megaptera novaeangliae), fin whales (Balaenoptera physalus), and minke whales (B. acutorostrata), was investigated at Cape Saint Francis, Newfoundland, Canada during the summers of 1995 and 1996. The influence of HAADs on baleen whale distribution, abundance, and behaviour was evaluated by shore-based monitoring of a study site. A HAADs system was moored inshore at a water depth of 10m and the average sound pressure level of these pulses was 194 dB re luPa at 1 m with energy concentrated around 10 kHz and a single harmonic at 20 kHz. The acoustic device was randomly operated on a 24 hour basis (either 'on' or 'off). Observers stationed on a 60m cliff documented species, number of individuals, behaviour and presence/absence of vessels in the area with each whale sighting throughout the day. Whale movements were tracked with a theodolite and observers were unaware of the operating condition of HAADs. The distance between whale sightings and HAADs was quantified to determine whale distribution, sighting rate was calculated as a measure of abundance, and the proportion of behaviours were compared between operating condition of HAADS. Results indicated that operation of HAADs was significantly related to the distribution and abundance of baleen whales and may relate to transient and residential species differently. Despite considerable variation in the number of whale sightings between years, overall distance and sighting trends suggest that humpback and fin whales demonstrated an avoidance of operating HAADs while minke whales exhibited no influence and/or an attraction to operating HAADs. This result suggests that transient whale species are displaced from areas with operating HAADs, while resident species remain in areas with operating HAADs. To mitigate any possible influences on baleen whales from HAADs, deterrent usage could be seasonally adjusted to avoid biologically important habitats and high concentrations of whales.

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