Concerning demographic limitations on the population growth rate of West Australian (breeding stock D) humpback whales

dc.contributor.authorBrandão, Anabela
dc.contributor.authorButterworth, Doug S
dc.date.accessioned2016-03-14T09:13:04Z
dc.date.available2016-03-14T09:13:04Z
dc.date.issued2011
dc.date.updated2016-03-14T09:08:34Z
dc.description.abstractThe upper bound of 0.126 on the maximum demographically possible annual growth rate for humpback whales that has standardly been imposed on recent applications of age-aggregated assessment models for this species in the IWC Scientific Committee, is based on an analysis that assumes steady age structure. It is conceivable that transient age-structure effects could admit greater population growth rates for short periods than suggested by such a bound. This possibility is addressed by developing an age-structured population model in which possible density dependent changes in pregnancy rate, age at first parturition and natural mortality are modelled explicitly, and allowance is made for the possibility of natural mortality increasing at older ages. The model is applied to the case of the west Australian humpback whale population (Breeding Stock D), for which breeding ground surveys over the 1982–1994 period provide a point estimate of 0.10 for the annual population growth rate. Results based upon the breeding population survey estimate of abundance of 10,032 in 1999 suggest that 0.12 is the maximum demographically feasible annual rate of increase for this stock over 1982–1994 if it is a closed population. This result is based on essentially the same parameter choices as led to the earlier r = 0.126 bound, i.e. that in the limit of low population size the age at first parturition approaches five years from above, the annual pregnancy rate 0.5 from below, and the annual natural mortality rate 0.01 from above. Transient effects do not appear able to reconcile the observed rate of increase with less extreme values of demographic parameters than led to the previously imposed upper bound of 0.126 on the maximum possible annual growth rate. Although use of extreme values reported for demographic parameters for Northern Hemisphere humpback whale populations, rather than those considered here, would reduce this suggested maximum rate of 0.12, the conclusion that transient effects have a very limited impact on observed population growth rates would be unlikely to change.en_ZA
dc.identifier.apacitationBrandão, A., & Butterworth, D. S. (2011). Concerning demographic limitations on the population growth rate of West Australian (breeding stock D) humpback whales. <i>Journal of Cetacean Research and Management (Special Issue)</i>, http://hdl.handle.net/11427/17754en_ZA
dc.identifier.chicagocitationBrandão, Anabela, and Doug S Butterworth "Concerning demographic limitations on the population growth rate of West Australian (breeding stock D) humpback whales." <i>Journal of Cetacean Research and Management (Special Issue)</i> (2011) http://hdl.handle.net/11427/17754en_ZA
dc.identifier.citationBrandão, A., & Butterworth, D. S. (2006). Concerning demographic limitations on the population growth rate of West Australian (Breeding Stock D) humpback whales. International Whaling Commission document: SC/58/SH24, 1-15.en_ZA
dc.identifier.issn1561-0713en_ZA
dc.identifier.ris TY - Journal Article AU - Brandão, Anabela AU - Butterworth, Doug S AB - The upper bound of 0.126 on the maximum demographically possible annual growth rate for humpback whales that has standardly been imposed on recent applications of age-aggregated assessment models for this species in the IWC Scientific Committee, is based on an analysis that assumes steady age structure. It is conceivable that transient age-structure effects could admit greater population growth rates for short periods than suggested by such a bound. This possibility is addressed by developing an age-structured population model in which possible density dependent changes in pregnancy rate, age at first parturition and natural mortality are modelled explicitly, and allowance is made for the possibility of natural mortality increasing at older ages. The model is applied to the case of the west Australian humpback whale population (Breeding Stock D), for which breeding ground surveys over the 1982–1994 period provide a point estimate of 0.10 for the annual population growth rate. Results based upon the breeding population survey estimate of abundance of 10,032 in 1999 suggest that 0.12 is the maximum demographically feasible annual rate of increase for this stock over 1982–1994 if it is a closed population. This result is based on essentially the same parameter choices as led to the earlier r = 0.126 bound, i.e. that in the limit of low population size the age at first parturition approaches five years from above, the annual pregnancy rate 0.5 from below, and the annual natural mortality rate 0.01 from above. Transient effects do not appear able to reconcile the observed rate of increase with less extreme values of demographic parameters than led to the previously imposed upper bound of 0.126 on the maximum possible annual growth rate. Although use of extreme values reported for demographic parameters for Northern Hemisphere humpback whale populations, rather than those considered here, would reduce this suggested maximum rate of 0.12, the conclusion that transient effects have a very limited impact on observed population growth rates would be unlikely to change. DA - 2011 DB - OpenUCT DP - University of Cape Town J1 - Journal of Cetacean Research and Management (Special Issue) LK - https://open.uct.ac.za PB - University of Cape Town PY - 2011 SM - 1561-0713 T1 - Concerning demographic limitations on the population growth rate of West Australian (breeding stock D) humpback whales TI - Concerning demographic limitations on the population growth rate of West Australian (breeding stock D) humpback whales UR - http://hdl.handle.net/11427/17754 ER - en_ZA
dc.identifier.urihttp://hdl.handle.net/11427/17754
dc.identifier.urihttps://iwc.int/journalspec03
dc.identifier.vancouvercitationBrandão A, Butterworth DS. Concerning demographic limitations on the population growth rate of West Australian (breeding stock D) humpback whales. Journal of Cetacean Research and Management (Special Issue). 2011; http://hdl.handle.net/11427/17754.en_ZA
dc.language.isoeng
dc.publisherInternational Whaling Commissionen_ZA
dc.publisher.departmentMarine Resource Assessment and Management Groupen_ZA
dc.publisher.facultyFaculty of Scienceen_ZA
dc.publisher.institutionUniversity of Cape Town
dc.sourceJournal of Cetacean Research and Management (Special Issue)en_ZA
dc.source.urihttps://iwc.int/journalspec03
dc.subject.otherHumpback Whale
dc.subject.otherSouthern Hemisphere
dc.subject.otherModelling
dc.subject.otherGrowth
dc.subject.otherPregnancy Rate
dc.subject.otherParturition
dc.titleConcerning demographic limitations on the population growth rate of West Australian (breeding stock D) humpback whalesen_ZA
dc.typeJournal Articleen_ZA
uct.subject.keywordsHumpback Whaleen_ZA
uct.subject.keywordsSouthern Hemisphereen_ZA
uct.subject.keywordsModellingen_ZA
uct.subject.keywordsGrowthen_ZA
uct.subject.keywordsPregnancy Rateen_ZA
uct.subject.keywordsParturitionen_ZA
uct.type.publicationResearchen_ZA
uct.type.resourceArticleen_ZA
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