Browsing by Subject "Balaenoptera musculus brevicauda"

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    Past and present distribution, densities and movements of blue whales Balaenoptera musculus in the Southern Hemisphere and northern Indian Ocean
    (Wiley, 2007) Branch, Trevor A; Stafford, K M; Palacios, D M; Allison, C; Bannister, J L; Burton, C L K; Cabrera, E; Carlson, C A; Galletti Vernazzani, B; Gill, P C; Hucke-Gaete, R; Jenner, K C S; Jenner, M N M; Matsuoka, K; Mikhalev, Y A; Miyashita, T; Morrice, M G; Nishiwaki, S; Sturrock, V J; Tormosov, D; Anderson, R C; Baker, A N; Best, P D; Borsa, P; Brownell Jr, R I; Childerhouse, S; Findlay, K P; Gerrodette, T; Ilangakoon, A D; Joergensen, M; Kahn, B; Ljungblad, D K; Maughan, B; Mccauley, R D; Mckay, S; Norris, T F; Oman Whale and Dolphin Research Group; Rankin, S; Samaran, F; Thiele, D; van Waerebeek, K; Warneke, R M
    1. Blue whale locations in the Southern Hemisphere and northern Indian Ocean were obtained from catches (303 239), sightings (4383 records of 8058 whales), strandings (103), Discovery marks (2191) and recoveries (95), and acoustic recordings. 2. Sighting surveys included 7 480 450 km of effort plus 14 676 days with unmeasured effort. Groups usually consisted of solitary whales (65.2%) or pairs (24.6%); larger feeding aggregations of unassociated individuals were only rarely observed. Sighting rates (groups per 1000 km from many platform types) varied by four orders of magnitude and were lowest in the waters of Brazil, South Africa, the eastern tropical Pacific, Antarctica and South Georgia; higher in the Subantarctic and Peru; and highest around Indonesia, Sri Lanka, Chile, southern Australia and south of Madagascar. 3. Blue whales avoid the oligotrophic central gyres of the Indian, Pacific and Atlantic Oceans, but are more common where phytoplankton densities are high, and where there are dynamic oceanographic processes like upwelling and frontal meandering. 4. Compared with historical catches, the Antarctic (‘true’) subspecies is exceedingly rare and usually concentrated closer to the summer pack ice. In summer they are found throughout the Antarctic; in winter they migrate to southern Africa (although recent sightings there are rare) and to other northerly locations (based on acoustics), although some overwinter in the Antarctic. 5. Pygmy blue whales are found around the Indian Ocean and from southern Australia to New Zealand. At least four groupings are evident: northern Indian Ocean, from Madagascar to the Subantarctic, Indonesia to western and southern Australia, and from New Zealand northwards to the equator. Sighting rates are typically much higher than for Antarctic blue whales.
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    Regional differences in length at sexual maturity for female blue whales based on recovered Soviet whaling data
    (Society for Marine Mammalogy, 2008) Branch, Trevor A; Mikhalev, Y A
    New blue whale ovarian corpora data from illegal Soviet catches in the Southern Hemisphere and northern Indian Ocean were recovered from the original logbooks. Catches north of 52°S were assumed to be pygmy blue whales (Balaenoptera musculus brevicauda, n= 1,272); those south of 56°S were assumed to be Antarctic (true) blue whales (B. m. intermedia, n= 153). Three probable Antarctic blue whales north of 52°S were excluded. Lengths at which 50% and 95% of females become sexually mature (L50 and L95) were estimated from a Bayesian logistic model. These estimates are more precise than previous Japanese estimates because Soviet catches below the legal minimum of 70 ft (21.3 m) were 32 times greater. For pygmy blue whales L50 was 19.2 m (95% interval 19.1–19.3 m) and L95 was 20.5 m (95% interval 20.4–20.7 m). Antarctic L50 (23.4 m, 95% interval 22.9–23.9 m) was much longer than L50 for pygmy blue whale regions (18.4–19.9 m). The median L50 for the northern Indian Ocean was 0.5–0.6 m shorter than for pygmy blue whales from other regions; although statistically significant, these small length differences provide little support for northern Indian Ocean blue whales being a separate subspecies, B. m. indica.