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Blue and fin whale acoustics and ecology off Antarctic Peninsula

  • Author(s): Širović, Ana
  • et al.
Abstract

Blue (Balaenoptera musculus) and fin whales (B. physalus) in the Southern Ocean were subjects of extensive whaling industry during the twentieth century. Their current population numbers remain low, making population monitoring using traditional visual surveys difficult. Both blue and fin whales produce low frequency, regularly repeated calls and are suitable for acoustic monitoring. Eight, continuously recording acoustic recorders were deployed off the Western Antarctic Peninsula (WAP) between March 2001 and February 2003. Ranges to calling blue and fin whales were calculated using hyperbolic localization and multipath arrivals up to the distances of 200 and 56km, respectively. Calls of both species had high intensity, blue whales calls had the average source level 189±3dB re: 1[mu]Pa at 1m and the average fin whale call source level was 189±4dB re: 1[mu]Pa at 1m. Automatic call detection methods were used for analysis of calling blue and fin whale seasonal presence and habitat preferences. Blue whale calls were detected year round, on average 177 days/ year, with peak calling in March and April, and a secondary peak in October and November. Fin whale calling rates were seasonal with calls detected between February and June (on average 51 days/year), and a peak in May. During the entire deployment period, detected calls from both species showed negative correlation with sea ice concentrations. Also, baleen whale sounds were recorded during multiple cruises off the Antarctic Peninsula using sonobuoys. Recordings from two fall cruises off the WAP were used for analyses of habitat preferences of calling blue and fin whales. The presence of calling blue whales was positively correlated with bottom depth and sea surface temperature, and negatively correlated with krill biomass in the top 100m and abundance of the rest of the zooplankton at depth (101-300m). Locations of fin whale calls were associated with a deep trough area and high Chl -a concentrations. Distribution of baleen whale calls recorded in the Scotia Sea (east of the Antarctic Peninsula) indicated that fin whales occur in open water, and blue, southern right (Eubalaena australis), minke (B. bonaerensis), and humpback whales (Megaptera novaeangliae) occur near islands or close to the ice edge

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