From both sides: dire demographic consequences of carnivorous mice and longlining for the critical endangered Tristan albatrosses on Gough Island

dc.contributor.authorWanless, Ross M
dc.contributor.authorRyan, Peter G
dc.contributor.authorAltwegg, Res
dc.contributor.authorAngel, Andrea
dc.contributor.authorCooper, John
dc.contributor.authorCuthbert, Richard
dc.contributor.authorHilton, Geoff M
dc.date.accessioned2018-09-25T14:39:03Z
dc.date.available2018-09-25T14:39:03Z
dc.date.issued2009
dc.date.updated2016-01-15T07:08:41Z
dc.description.abstractThe IUCN recently uplisted the Tristan albatross (Diomedea dabbenena) to Critically Endangered. Here we present new data indicating negative population trends on Gough Island arising from low adult survival (∼91%, ascribed to accidental mortality on fishing gear) and low breeding success (averaging 32%, due to mouse predation). Fledgling production from 1979 to 2007 and numbers of incubating adults from 1956 to 2007 have both decreased by ∼1% p.a. Consecutive annual counts of incubating adults and a population model permit the first reliable estimates of the Tristan albatross population, presently 5400 breeding adults and 11,300 birds in all age- and stage-classes. Population models explore scenarios of likely demographic trends using combinations of hypothetical best-case estimates vs. observed estimates for two key parameters: adult survival and breeding success. These scenarios highlight the relative benefits to the species of eradicating mice or mitigating bycatch. The model scenario using observed estimates predicts annual growth rate at −2.85%. Adult survival rates have probably decreased in recent years, concomitant with increased longline fishing effort, which might explain the discrepancy between counts and modelled trends. Negative trends cannot be reversed by improving breeding success alone, and adult survival must exceed an improbable 97% to balance the current chick production. A worst-case scenario including a fixed number of adult deaths annually predicted a catastrophic 4.2% p.a. decrease and extinction in ∼30 years. Population growth was most sensitive to adult survival, but even using an adult survival estimate without fishery mortality, current breeding success is insufficient to maintain the population. These findings do not support the ‘compensatory mitigation of bycatch’ model (offsetting bycatch impacts by eradicating invasive species), and the impacts of both fishery mortality and mouse predation must be addressed to improve the conservation status of the Critically Endangered Tristan albatross.
dc.identifierhttp://dx.doi.org/10.1016/j.biocon.2009.03.008
dc.identifier.apacitationWanless, R. M., Ryan, P. G., Altwegg, R., Angel, A., Cooper, J., Cuthbert, R., & Hilton, G. M. (2009). From both sides: dire demographic consequences of carnivorous mice and longlining for the critical endangered Tristan albatrosses on Gough Island. <i>Biological Conservation</i>, http://hdl.handle.net/11427/28495en_ZA
dc.identifier.chicagocitationWanless, Ross M, Peter G Ryan, Res Altwegg, Andrea Angel, John Cooper, Richard Cuthbert, and Geoff M Hilton "From both sides: dire demographic consequences of carnivorous mice and longlining for the critical endangered Tristan albatrosses on Gough Island." <i>Biological Conservation</i> (2009) http://hdl.handle.net/11427/28495en_ZA
dc.identifier.citationWanless, R. M., Ryan, P. G., Altwegg, R., Angel, A., Cooper, J., Cuthbert, R., & Hilton, G. M. (2009). From both sides: dire demographic consequences of carnivorous mice and longlining for the critically endangered Tristan albatrosses on Gough Island. Biological Conservation, 142(8), 1710-1718.
dc.identifier.ris TY - AU - Wanless, Ross M AU - Ryan, Peter G AU - Altwegg, Res AU - Angel, Andrea AU - Cooper, John AU - Cuthbert, Richard AU - Hilton, Geoff M AB - The IUCN recently uplisted the Tristan albatross (Diomedea dabbenena) to Critically Endangered. Here we present new data indicating negative population trends on Gough Island arising from low adult survival (∼91%, ascribed to accidental mortality on fishing gear) and low breeding success (averaging 32%, due to mouse predation). Fledgling production from 1979 to 2007 and numbers of incubating adults from 1956 to 2007 have both decreased by ∼1% p.a. Consecutive annual counts of incubating adults and a population model permit the first reliable estimates of the Tristan albatross population, presently 5400 breeding adults and 11,300 birds in all age- and stage-classes. Population models explore scenarios of likely demographic trends using combinations of hypothetical best-case estimates vs. observed estimates for two key parameters: adult survival and breeding success. These scenarios highlight the relative benefits to the species of eradicating mice or mitigating bycatch. The model scenario using observed estimates predicts annual growth rate at −2.85%. Adult survival rates have probably decreased in recent years, concomitant with increased longline fishing effort, which might explain the discrepancy between counts and modelled trends. Negative trends cannot be reversed by improving breeding success alone, and adult survival must exceed an improbable 97% to balance the current chick production. A worst-case scenario including a fixed number of adult deaths annually predicted a catastrophic 4.2% p.a. decrease and extinction in ∼30 years. Population growth was most sensitive to adult survival, but even using an adult survival estimate without fishery mortality, current breeding success is insufficient to maintain the population. These findings do not support the ‘compensatory mitigation of bycatch’ model (offsetting bycatch impacts by eradicating invasive species), and the impacts of both fishery mortality and mouse predation must be addressed to improve the conservation status of the Critically Endangered Tristan albatross. DA - 2009 DB - OpenUCT DP - University of Cape Town J1 - Biological Conservation LK - https://open.uct.ac.za PB - University of Cape Town PY - 2009 T1 - From both sides: dire demographic consequences of carnivorous mice and longlining for the critical endangered Tristan albatrosses on Gough Island TI - From both sides: dire demographic consequences of carnivorous mice and longlining for the critical endangered Tristan albatrosses on Gough Island UR - http://hdl.handle.net/11427/28495 ER - en_ZA
dc.identifier.urihttp://hdl.handle.net/11427/28495
dc.identifier.vancouvercitationWanless RM, Ryan PG, Altwegg R, Angel A, Cooper J, Cuthbert R, et al. From both sides: dire demographic consequences of carnivorous mice and longlining for the critical endangered Tristan albatrosses on Gough Island. Biological Conservation. 2009; http://hdl.handle.net/11427/28495.en_ZA
dc.language.isoeng
dc.publisher.departmentDepartment of Biological Sciencesen_ZA
dc.publisher.facultyFaculty of Scienceen_ZA
dc.publisher.institutionUniversity of Cape Town
dc.sourceBiological Conservation
dc.source.urihttps://www.journals.elsevier.com/biological-conservation
dc.subject.otherDemography
dc.subject.otherPopulation model
dc.subject.otherExtinction risk
dc.subject.otherConservation
dc.subject.otherSeabird
dc.titleFrom both sides: dire demographic consequences of carnivorous mice and longlining for the critical endangered Tristan albatrosses on Gough Island
dc.typeJournal Article
uct.type.filetypeText
uct.type.filetypeImage
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