Updated estimates of demographic parameters for Southern right whales off South Africa

dc.contributor.authorBest, Peter B
dc.contributor.authorBrandão, Anabela
dc.contributor.authorButterworth, Doug S
dc.date.accessioned2016-03-08T14:00:58Z
dc.date.available2016-03-08T14:00:58Z
dc.date.issued2005
dc.date.updated2016-02-25T10:41:47Z
dc.description.abstractAerial counts of right whale cow-calf pairs on the south coast of South Africa between 1971 and 2003 indicate an annual instantaneous population increase rate of 0.069 a year (SE 0.003) over this period. Annual photographic surveys since 1979 have resulted in 1,504 resightings of 793 individual cows with calves. Observed calving intervals ranged from 2 to 23 years, with a principal mode at 3 years and secondary modes at 6 and 9 years, but these made no allowance for missed calvings. Using the model of Payne et al. (1990), a maximum calving interval of 5 years produces the most appropriate fit to the data, giving a mean calving interval of 3.15 years with a 95 % confidence interval of (3.11, 3.18). The same model produces an estimate for adult female survival rate of 0.990 with a 95% confidence interval of (0.983, 0.997). The Payne et al. (1990) model is extended to incorporate information on the observed ages of first reproduction of greyblazed calves, which are known to be female. This allows the estimation of first parturition (median 7.69 years with 95% confidence interval (7.06, 8.32)). First year survival rate was estimated as 0.734 (0.518, 0.95) and the instantaneous population increase rate 0.073 (0.066, 0.079). The current population is estimated as some 3,400 animals, or about 17% of initial population size: the latter parameter needs re-consideration.
dc.identifier.apacitationBest, P. B., Brandão, A., & Butterworth, D. S. (2005). <i>Updated estimates of demographic parameters for Southern right whales off South Africa</i> International Whaling Commission. Retrieved from http://hdl.handle.net/11427/17582en_ZA
dc.identifier.chicagocitationBest, Peter B, Anabela Brandão, and Doug S Butterworth <i>Updated estimates of demographic parameters for Southern right whales off South Africa.</i> International Whaling Commission, 2005. http://hdl.handle.net/11427/17582en_ZA
dc.identifier.citationBest, P. B., Brandão, A., & Butterworth, D. S. (2005). Updated estimates of demographic parameters for southern right whales off South Africa. International Whaling Commission document: SC/57/BRG2, 1-17.en_ZA
dc.identifier.ris TY - Working Paper AU - Best, Peter B AU - Brandão, Anabela AU - Butterworth, Doug S AB - Aerial counts of right whale cow-calf pairs on the south coast of South Africa between 1971 and 2003 indicate an annual instantaneous population increase rate of 0.069 a year (SE 0.003) over this period. Annual photographic surveys since 1979 have resulted in 1,504 resightings of 793 individual cows with calves. Observed calving intervals ranged from 2 to 23 years, with a principal mode at 3 years and secondary modes at 6 and 9 years, but these made no allowance for missed calvings. Using the model of Payne et al. (1990), a maximum calving interval of 5 years produces the most appropriate fit to the data, giving a mean calving interval of 3.15 years with a 95 % confidence interval of (3.11, 3.18). The same model produces an estimate for adult female survival rate of 0.990 with a 95% confidence interval of (0.983, 0.997). The Payne et al. (1990) model is extended to incorporate information on the observed ages of first reproduction of greyblazed calves, which are known to be female. This allows the estimation of first parturition (median 7.69 years with 95% confidence interval (7.06, 8.32)). First year survival rate was estimated as 0.734 (0.518, 0.95) and the instantaneous population increase rate 0.073 (0.066, 0.079). The current population is estimated as some 3,400 animals, or about 17% of initial population size: the latter parameter needs re-consideration. DA - 2005 DB - OpenUCT DP - University of Cape Town KW - demographic parameters KW - South Africa LK - https://open.uct.ac.za PB - University of Cape Town PY - 2005 T1 - Updated estimates of demographic parameters for Southern right whales off South Africa TI - Updated estimates of demographic parameters for Southern right whales off South Africa UR - http://hdl.handle.net/11427/17582 ER - en_ZA
dc.identifier.urihttp://hdl.handle.net/11427/17582
dc.identifier.vancouvercitationBest PB, Brandão A, Butterworth DS. Updated estimates of demographic parameters for Southern right whales off South Africa. 2005 [cited yyyy month dd]. Available from: http://hdl.handle.net/11427/17582en_ZA
dc.languageengen_ZA
dc.publisherInternational Whaling Commission
dc.publisher.departmentMarine Resource Assessment and Management Groupen_ZA
dc.publisher.facultyFaculty of Scienceen_ZA
dc.publisher.institutionUniversity of Cape Town
dc.subjectdemographic parametersen_ZA
dc.subjectSouth Africaen_ZA
dc.subject.otherSouthern right whales
dc.titleUpdated estimates of demographic parameters for Southern right whales off South Africaen_ZA
dc.typeWorking Paperen_ZA
uct.type.filetypeText
uct.type.filetypeImage
uct.type.publicationResearchen_ZA
uct.type.resourceDiscussion paperen_ZA
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