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Publication Details
AFRICAN RESEARCH NEXUS
SHINING A SPOTLIGHT ON AFRICAN RESEARCH
agricultural and biological sciences
Separating southern blue whale subspecies based on length frequencies of sexually mature females
Marine Mammal Science, Volume 23, No. 4, Year 2007
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Description
When sexually mature, Antarctic (true) blue whales are substantially longer than pygmy blue whales. To estimate the proportions of these two subspecies in various regions, Bayesian mixture models were fitted to catch length frequencies of sexually mature females. The extent of rounding to 5-ft intervals was also estimated. Antarctic blue whales dominated (99.2%) pelagic catches south of 52°S, whereas pygmy blue whales dominated (99.9%) north of 52°S and in 35°-180°E. South of 60°S, only 0.7% (95% credibility interval 0.5%-1.0%) were pygmy blue whales, lower than the 7% upper bound currently assumed. Shore-based catches from SW Africa and those before 1937 from South Georgia and the South Shetlands were estimated to contain 90%-92% Antarctic blue whales. Actual proportions were probably higher, but these data show evidence of rounding (up to 19% of records), poor length-estimation methods, and other problems. The mean length of sexually mature female Chilean blue whales (77.1 ft, 23.5 m) was intermediate between pygmy (68.9 ft, 21.0 m) and Antarctic blue whales (83.4-86.3 ft, 25.4-26.6 m). A good fit to these data was obtained only by assuming that the Chilean whales are a separate subspecies or distinctive population. This finding is also consistent with their discrete distribution, and genetic and call type differences, compared to Antarctic and pygmy blue whales. © 2007 by the Society for Marine Mammalogy.
Authors & Co-Authors
Branch, Trevor A.
South Africa, Cape Town
University of Cape Town
Abubaker, E. M.N.
South Africa, Muizenberg
African Institute for Mathematical Sciences
Sudan, Khartoum
Khartoum University
Mkango, S.
South Africa, Cape Town
University of Cape Town
South Africa, Muizenberg
African Institute for Mathematical Sciences
Butterworth, Douglas S.
South Africa, Cape Town
University of Cape Town
Statistics
Citations: 88
Authors: 4
Affiliations: 3
Identifiers
Doi:
10.1111/j.1748-7692.2007.00137.x
ISSN:
08240469
e-ISSN:
17487692
Research Areas
Genetics And Genomics
Study Design
Cross Sectional Study
Participants Gender
Female