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| Samaran, Flore; Stafford, Kathleen M.; Branch, Trevor A.; Gedamke, Jason; Royer, Jean-yves; Dziak, Robert P.; Guinet, Christophe. |
| Understanding the seasonal movements and distribution patterns of migratory species over ocean basin scales is vital for appropriate conservation and management measures. However, assessing populations over remote regions is challenging, particularly if they are rare. Blue whales (Balaenoptera musculus spp) are an endangered species found in the Southern and Indian Oceans. Here two recognized subspecies of blue whales and, based on passive acoustic monitoring, four "acoustic populations" occur. Three of these are pygmy blue whale (B. m. brevicauda) populations while the fourth is the Antarctic blue whale (B. m. intermedia). Past whaling catches have dramatically reduced their numbers but recent acoustic recordings show that these oceans are still important... |
| Tipo: Text |
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| Ano: 2013 |
URL: https://archimer.ifremer.fr/doc/00274/38490/36960.pdf |
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| Leroy, Emmanuelle C.; Samaran, Flore; Stafford, Kathleen M.; Bonnel, Julien; Royer, Jean-yves. |
| The southern Indian Ocean is believed to be a natural territory for blue and fin whales. However, decades after commercial and illegal whaling decimated these populations, little is known about their current status, seasonal habitat or movements. Recent passive acoustic studies have described the presence of 4 acoustic populations of blue whales (Antarctic and 3 'pygmy' types), but are generally limited temporally and geographically. Here, we examine up to 7 yr of continuous acoustic recordings (2010-2016) from a hydrophone network of 6 widely spaced sites in the southern Indian Ocean, looking for the presence of Antarctic and pygmy blue and fin whales. Power spectral density analyses of characteristic and distinct frequency bands of these species show... |
| Tipo: Text |
Palavras-chave: Pygmy blue whales; Antarctic blue whales; Fin whales; Southern Indian Ocean; Passive acoustic monitoring; Sympatry. |
| Ano: 2018 |
URL: https://archimer.ifremer.fr/doc/00516/62731/67110.pdf |
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| Leroy, Emmanuelle C; Royer, Jean-yves; Bonnel, Julien; Samaran, Flore. |
| In the past decades, in the context of a changing ocean submitted to an increasing human activity, a progressive decrease in the frequencies (pitch) of blue whale vocalizations has been observed worldwide. Its causes, of natural or anthropogenic nature, are still unclear. Based on 7years of continuous acoustic recordings at widespread sites in the southern Indian Ocean, we show that this observation stands for five populations of large whales. The frequency of selected units of vocalizations of fin, Antarctic, and pygmy blue whales has steadily decreased at a rate of a few tenths of hertz per year since 2002. In addition to this interannual frequency decrease, blue whale vocalizations display seasonal frequency shifts. We show that these intra-annual... |
| Tipo: Text |
Palavras-chave: Large baleen whales; Blue whale calls; Frequency shifts; Frequency decrease; Ambient noise; Bioacoustics. |
| Ano: 2018 |
URL: https://archimer.ifremer.fr/doc/00516/62730/67109.pdf |
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| Leroy, Emmanuelle C.; Samaran, Flore; Bonnel, Julien; Royer, Jean-yves. |
| Passive acoustic monitoring is an efficient way to provide insights on the ecology of large whales. This approach allows for long-term and species-specific monitoring over large areas. In this study, we examined six years (2010 to 2015) of continuous acoustic recordings at up to seven different locations in the Central and Southern Indian Basin to assess the peak periods of presence, seasonality and migration movements of Antarctic blue whales (Balaenoptera musculus intermedia). An automated method is used to detect the Antarctic blue whale stereotyped call, known as Z-call. Detection results are analyzed in terms of distribution, seasonal presence and diel pattern of emission at each site. Z-calls are detected year-round at each site, except for one... |
| Tipo: Text |
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| Ano: 2016 |
URL: https://archimer.ifremer.fr/doc/00357/46828/46699.pdf |
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