Revised estimates of abundance of South African sardine and anchovy from acoustic surveys adjusting for echosounder saturation in earlier surveys and attenuation effects for sardine

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dc.contributor.authorDe Moor, Carryn L
dc.contributor.authorButterworth, Doug S
dc.contributor.authorCoetzee, J C
dc.date.accessioned2016-03-11T10:08:31Z
dc.date.available2016-03-11T10:08:31Z
dc.date.issued2008
dc.date.updated2016-03-11T09:59:52Z
dc.description.abstractHydro-acoustic surveys have been used to provide annual estimates of May recruitment and November spawner biomass of the South African sardine Sardinops sagax and anchovy Engraulis encrasicolus resources since 1984. These time-series of abundance estimates form the backbone of the assessment of these resources, and consequently the management of the South African sardine and anchovy is critically dependent on them. Upgrades to survey equipment over time have resulted in recent surveys providing more accurate estimates of abundance, yet in order to maintain comparability across the full time-series, estimates of biomass mimicking the old equipment were used for a number of years. In this paper we develop a method to revise the earlier part of the time-series to correct for receiver saturation in the older generation SIMRAD EK400 and EKS-38 echo sounders and to account for attenuation in dense sardine schools. This is applied to provide a revised time-series of biomass estimates for the South African sardine and anchovy resources with associated variance–covariance matrices. Furthermore, the time-series presented here are based on updated acoustic target strength estimates, making this the most reliable time-series currently available for both resources.en_ZA
dc.identifierhttp://dx.doi.org/10.2989/AJMS.2008.30.2.2.552
dc.identifier.apacitationDe Moor, C. L., Butterworth, D. S., & Coetzee, J. C. (2008). Revised estimates of abundance of South African sardine and anchovy from acoustic surveys adjusting for echosounder saturation in earlier surveys and attenuation effects for sardine. <i>African Journal of Marine Science</i>, http://hdl.handle.net/11427/17634en_ZA
dc.identifier.chicagocitationDe Moor, Carryn L, Doug S Butterworth, and J C Coetzee "Revised estimates of abundance of South African sardine and anchovy from acoustic surveys adjusting for echosounder saturation in earlier surveys and attenuation effects for sardine." <i>African Journal of Marine Science</i> (2008) http://hdl.handle.net/11427/17634en_ZA
dc.identifier.citationDe Moor, C. L., Butterworth, D. S., & Coetzee, J. C. (2008). Revised estimates of abundance of South African sardine and anchovy from acoustic surveys adjusting for echosounder saturation in earlier surveys and attenuation effects for sardine. African Journal of Marine Science, 30(2), 219-232.en_ZA
dc.identifier.issn1814-232Xen_ZA
dc.identifier.ris TY - Journal Article AU - De Moor, Carryn L AU - Butterworth, Doug S AU - Coetzee, J C AB - Hydro-acoustic surveys have been used to provide annual estimates of May recruitment and November spawner biomass of the South African sardine Sardinops sagax and anchovy Engraulis encrasicolus resources since 1984. These time-series of abundance estimates form the backbone of the assessment of these resources, and consequently the management of the South African sardine and anchovy is critically dependent on them. Upgrades to survey equipment over time have resulted in recent surveys providing more accurate estimates of abundance, yet in order to maintain comparability across the full time-series, estimates of biomass mimicking the old equipment were used for a number of years. In this paper we develop a method to revise the earlier part of the time-series to correct for receiver saturation in the older generation SIMRAD EK400 and EKS-38 echo sounders and to account for attenuation in dense sardine schools. This is applied to provide a revised time-series of biomass estimates for the South African sardine and anchovy resources with associated variance–covariance matrices. Furthermore, the time-series presented here are based on updated acoustic target strength estimates, making this the most reliable time-series currently available for both resources. DA - 2008 DB - OpenUCT DP - University of Cape Town J1 - African Journal of Marine Science LK - https://open.uct.ac.za PB - University of Cape Town PY - 2008 SM - 1814-232X T1 - Revised estimates of abundance of South African sardine and anchovy from acoustic surveys adjusting for echosounder saturation in earlier surveys and attenuation effects for sardine TI - Revised estimates of abundance of South African sardine and anchovy from acoustic surveys adjusting for echosounder saturation in earlier surveys and attenuation effects for sardine UR - http://hdl.handle.net/11427/17634 ER - en_ZA
dc.identifier.urihttp://hdl.handle.net/11427/17634
dc.identifier.urihttp://www.tandfonline.com/doi/abs/10.2989/AJMS.2008.30.2.2.552
dc.identifier.vancouvercitationDe Moor CL, Butterworth DS, Coetzee JC. Revised estimates of abundance of South African sardine and anchovy from acoustic surveys adjusting for echosounder saturation in earlier surveys and attenuation effects for sardine. African Journal of Marine Science. 2008; http://hdl.handle.net/11427/17634.en_ZA
dc.languageengen_ZA
dc.publisherNational Inquiry Services Centre (NISC)en_ZA
dc.publisher.departmentMarine Resource Assessment and Management Groupen_ZA
dc.publisher.facultyFaculty of Scienceen_ZA
dc.publisher.institutionUniversity of Cape Town
dc.sourceAfrican Journal of Marine Scienceen_ZA
dc.source.urihttp://www.tandfonline.com/toc/tams20/current
dc.titleRevised estimates of abundance of South African sardine and anchovy from acoustic surveys adjusting for echosounder saturation in earlier surveys and attenuation effects for sardineen_ZA
dc.typeJournal Articleen_ZA
uct.subject.keywordsAcoustic surveyen_ZA
uct.subject.keywordsAnchovyen_ZA
uct.subject.keywordsAttenuationen_ZA
uct.subject.keywordsCalibration adjustmenten_ZA
uct.subject.keywordsRegressionen_ZA
uct.subject.keywordsSardineen_ZA
uct.subject.keywordsSaturationen_ZA
uct.type.filetypeText
uct.type.filetypeImage
uct.type.publicationResearchen_ZA
uct.type.resourceArticleen_ZA
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