Publication Date:
2022-05-25
Description:
© The Author(s), 2018. This article is distributed under the terms of the Creative Commons Attribution License. The definitive version was published in Broad-scale study of the seasonal and geographic occurrence of blue and fin whales in the Southern Indian Ocean. Endang Species Res 37 (2018):289-300, doi:10.3354/esr00927.
Description:
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 seasonal and geographic differences among the different populations, and the overall patterns for each display interannual consistencies in timing and occurrence. Antarctic blue and fin whales are recorded across the hydrophone network, mainly from austral autumn to spring, with peak intensity in winter. Pygmy blue whales show spatial variation: Madagascan
pygmy blue whales are mainly present in the west of the network, while the Australian call type is heard at the eastern sites. Both populations share a common seasonality, with a presence from January to June. Finally, the Sri Lankan call type is recorded only on a single site in the northeast. These results confirm the importance of the southern Indian Ocean for several populations of
endangered large whales and present the first long-term assessment of fin whales in the southern Indian Ocean.
Description:
The authors thank the captains and crew of RV ‘Marion Dufresne’ for the successful deployments and recoveries of the hydrophones of the OHASISBIO 298 Leroy et al.: Distribution of blue and fin whales experiment (http://dx.doi.org/10.18142/229). French cruises were funded by the French Polar Institute (IPEV), with additional support from INSU-CNRS. E.C.L. was supported by a PhD fellowship from the University of Brest and from the Regional Council of Brittany (Conseil Régional de Bretagne). K.M.S. contributed to this paper while staying at the University of Brest as Invited Professor. J.B. acknowledges funding from the Independent Research and Development Program at WHOI. The contribution of Mickael Beauverger at LGO to the logistics and deployment cruises is greatly appreciated.
Keywords:
Pygmy blue whale
;
Antarctic blue whales
;
Fin whales
;
Southern Indian Ocean
;
Passive acoustic monitoring
;
Sympatry
Repository Name:
Woods Hole Open Access Server
Type:
Article
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