Day-night differences in Cunene horse mackerel (Trachurus trecae) acoustic relative densities off Angola
Autor(a) principal: | |
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Data de Publicação: | 2010 |
Outros Autores: | , |
Tipo de documento: | Artigo |
Idioma: | eng |
Título da fonte: | Repositório Científico de Acesso Aberto de Portugal (Repositórios Cientìficos) |
Texto Completo: | http://hdl.handle.net/10400.1/11475 |
Resumo: | The assessment and the management of the Cunene horse mackerel in Angola rely heavily on abundance estimates from hydroacoustic surveys. Acoustic data collected from 1994 to 1999 were analysed to quantify diurnal variation in relative acoustic densities at 38 kHz. The nautical-area scattering coefficient (s(A), m(2) nautical mile(-2)) was characterized by clear day night differences: s(A) values recorded during the day were significantly higher (mean s(A): 135 m(2) nautical mile(-2)) than the corresponding night-time values (mean s(A) 83 m(2) nautical mile(-2)). This pattern is associated with differences in behaviour and horizontal and vertical distributions between day and night: by day, the fish school near the seabed, and by night, they move into the pelagic zone and disperse into widespread scattering layers. More than 40% of the total backscatter by day originated from the bottom 10 m, but at night this proportion decreased to <10%. The findings demonstrate considerable influences of behaviour and aggregation dynamics on acoustic measurements. Possible implications for the estimates of acoustic abundance are discussed in the light of the differences. |
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Day-night differences in Cunene horse mackerel (Trachurus trecae) acoustic relative densities off AngolaTarget strengthsEcho integratorFish behaviorPelagic fishThe assessment and the management of the Cunene horse mackerel in Angola rely heavily on abundance estimates from hydroacoustic surveys. Acoustic data collected from 1994 to 1999 were analysed to quantify diurnal variation in relative acoustic densities at 38 kHz. The nautical-area scattering coefficient (s(A), m(2) nautical mile(-2)) was characterized by clear day night differences: s(A) values recorded during the day were significantly higher (mean s(A): 135 m(2) nautical mile(-2)) than the corresponding night-time values (mean s(A) 83 m(2) nautical mile(-2)). This pattern is associated with differences in behaviour and horizontal and vertical distributions between day and night: by day, the fish school near the seabed, and by night, they move into the pelagic zone and disperse into widespread scattering layers. More than 40% of the total backscatter by day originated from the bottom 10 m, but at night this proportion decreased to <10%. The findings demonstrate considerable influences of behaviour and aggregation dynamics on acoustic measurements. Possible implications for the estimates of acoustic abundance are discussed in the light of the differences.Norwegian Agency for Development Cooperation (NORAD); Dr Fridtjof Nansen programme; Gulbenkian FoundationOxford University PressSapientiaVelho, Filomena VazBarros, PedroAxelsen, Bjorn Erik2018-12-07T14:53:21Z2010-072010-07-01T00:00:00Zinfo:eu-repo/semantics/publishedVersioninfo:eu-repo/semantics/articleapplication/pdfhttp://hdl.handle.net/10400.1/11475eng1054-313910.1093/icesjms/fsq004info:eu-repo/semantics/openAccessreponame:Repositório Científico de Acesso Aberto de Portugal (Repositórios Cientìficos)instname:Agência para a Sociedade do Conhecimento (UMIC) - FCT - Sociedade da Informaçãoinstacron:RCAAP2023-07-24T10:23:17Zoai:sapientia.ualg.pt:10400.1/11475Portal AgregadorONGhttps://www.rcaap.pt/oai/openaireopendoar:71602024-03-19T20:02:58.621898Repositório Científico de Acesso Aberto de Portugal (Repositórios Cientìficos) - Agência para a Sociedade do Conhecimento (UMIC) - FCT - Sociedade da Informaçãofalse |
dc.title.none.fl_str_mv |
Day-night differences in Cunene horse mackerel (Trachurus trecae) acoustic relative densities off Angola |
title |
Day-night differences in Cunene horse mackerel (Trachurus trecae) acoustic relative densities off Angola |
spellingShingle |
Day-night differences in Cunene horse mackerel (Trachurus trecae) acoustic relative densities off Angola Velho, Filomena Vaz Target strengths Echo integrator Fish behavior Pelagic fish |
title_short |
Day-night differences in Cunene horse mackerel (Trachurus trecae) acoustic relative densities off Angola |
title_full |
Day-night differences in Cunene horse mackerel (Trachurus trecae) acoustic relative densities off Angola |
title_fullStr |
Day-night differences in Cunene horse mackerel (Trachurus trecae) acoustic relative densities off Angola |
title_full_unstemmed |
Day-night differences in Cunene horse mackerel (Trachurus trecae) acoustic relative densities off Angola |
title_sort |
Day-night differences in Cunene horse mackerel (Trachurus trecae) acoustic relative densities off Angola |
author |
Velho, Filomena Vaz |
author_facet |
Velho, Filomena Vaz Barros, Pedro Axelsen, Bjorn Erik |
author_role |
author |
author2 |
Barros, Pedro Axelsen, Bjorn Erik |
author2_role |
author author |
dc.contributor.none.fl_str_mv |
Sapientia |
dc.contributor.author.fl_str_mv |
Velho, Filomena Vaz Barros, Pedro Axelsen, Bjorn Erik |
dc.subject.por.fl_str_mv |
Target strengths Echo integrator Fish behavior Pelagic fish |
topic |
Target strengths Echo integrator Fish behavior Pelagic fish |
description |
The assessment and the management of the Cunene horse mackerel in Angola rely heavily on abundance estimates from hydroacoustic surveys. Acoustic data collected from 1994 to 1999 were analysed to quantify diurnal variation in relative acoustic densities at 38 kHz. The nautical-area scattering coefficient (s(A), m(2) nautical mile(-2)) was characterized by clear day night differences: s(A) values recorded during the day were significantly higher (mean s(A): 135 m(2) nautical mile(-2)) than the corresponding night-time values (mean s(A) 83 m(2) nautical mile(-2)). This pattern is associated with differences in behaviour and horizontal and vertical distributions between day and night: by day, the fish school near the seabed, and by night, they move into the pelagic zone and disperse into widespread scattering layers. More than 40% of the total backscatter by day originated from the bottom 10 m, but at night this proportion decreased to <10%. The findings demonstrate considerable influences of behaviour and aggregation dynamics on acoustic measurements. Possible implications for the estimates of acoustic abundance are discussed in the light of the differences. |
publishDate |
2010 |
dc.date.none.fl_str_mv |
2010-07 2010-07-01T00:00:00Z 2018-12-07T14:53:21Z |
dc.type.status.fl_str_mv |
info:eu-repo/semantics/publishedVersion |
dc.type.driver.fl_str_mv |
info:eu-repo/semantics/article |
format |
article |
status_str |
publishedVersion |
dc.identifier.uri.fl_str_mv |
http://hdl.handle.net/10400.1/11475 |
url |
http://hdl.handle.net/10400.1/11475 |
dc.language.iso.fl_str_mv |
eng |
language |
eng |
dc.relation.none.fl_str_mv |
1054-3139 10.1093/icesjms/fsq004 |
dc.rights.driver.fl_str_mv |
info:eu-repo/semantics/openAccess |
eu_rights_str_mv |
openAccess |
dc.format.none.fl_str_mv |
application/pdf |
dc.publisher.none.fl_str_mv |
Oxford University Press |
publisher.none.fl_str_mv |
Oxford University Press |
dc.source.none.fl_str_mv |
reponame:Repositório Científico de Acesso Aberto de Portugal (Repositórios Cientìficos) instname:Agência para a Sociedade do Conhecimento (UMIC) - FCT - Sociedade da Informação instacron:RCAAP |
instname_str |
Agência para a Sociedade do Conhecimento (UMIC) - FCT - Sociedade da Informação |
instacron_str |
RCAAP |
institution |
RCAAP |
reponame_str |
Repositório Científico de Acesso Aberto de Portugal (Repositórios Cientìficos) |
collection |
Repositório Científico de Acesso Aberto de Portugal (Repositórios Cientìficos) |
repository.name.fl_str_mv |
Repositório Científico de Acesso Aberto de Portugal (Repositórios Cientìficos) - Agência para a Sociedade do Conhecimento (UMIC) - FCT - Sociedade da Informação |
repository.mail.fl_str_mv |
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1799133264274784256 |