Changes in the distribution of sardine eggs and larvae off Portugal, 1985-2000

Generalized additive models (GAMs) were fitted to sardine (Sardina pilchardus) egg distribution data from three daily egg production method surveys. The results showed that the area of egg cover off Portugal decreased significantly from 11 800 km2 in 1988 to 7000 km2 in 1997 and 7400 km2 in 1999. Th...

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Authors: Stratoudakis, Yorgos, Bernal, M., Borchers, David, Borges, María de Fátima, Cardador, Fátima
Format: article
Publication Date:2003
Country:España
Institution:Consejo Superior de Investigaciones Científicas (CSIC)
Repository:DIGITAL.CSIC. Repositorio Institucional del CSIC
OAI Identifier:oai:digital.csic.es:10261/325357
Online Access:http://hdl.handle.net/10261/325357
Access Level:Open access
Keyword:Centro Oceanográfico de Cádiz
Pesquerías
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oai_identifier_str oai:digital.csic.es:10261/325357
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spelling Changes in the distribution of sardine eggs and larvae off Portugal, 1985-2000Stratoudakis, YorgosBernal, M.Borchers, DavidBorges, María de FátimaCardador, FátimaCentro Oceanográfico de CádizPesqueríasGeneralized additive models (GAMs) were fitted to sardine (Sardina pilchardus) egg distribution data from three daily egg production method surveys. The results showed that the area of egg cover off Portugal decreased significantly from 11 800 km2 in 1988 to 7000 km2 in 1997 and 7400 km2 in 1999. This is because of a significant reduction in sardine egg presence off northern Portugal, GAM estimated areas being similar or higher in the late 1990s for southwestern and southern Portugal. The distributional area covered by larvae was not estimated for 1988 (larval distribution extended beyond the survey area), although it was probably higher than the 9600 km2 for 1997 and 5500 km2 for 1999. In 1997 and 1999, the Gulf of Cadiz was also sampled, indicating extensive areas with sardine eggs and larvae (more than 50% of the total area of distribution off Portugal). Standardized data from 15 ichthyoplankton surveys between 1985 and 2000 show a decline in the mean probability of egg presence within the Portuguese continental shelf from the mid-1980s to the late-1990s, because of a marked reduction in egg presence off northern Portugal. Sardine larval data from the same surveys suggest that the reduction in mean probability of presence in the north is less marked than for eggs (although this comparison ignores the presence of sardine larvae beyond the continental shelf in the 1980s). Similar changes off northern Portugal and western Galicia are observed in commercial sardine catches and the acoustically estimated area of fish distribution. It is possible that the observed decline in spawning area off northwestern Iberia during the 1990s is indirectly reflecting the prevalence of environmental conditions detrimental to sardine recruitment (northerly winds during winter that favour coastal upwelling and offshore transport), which have reduced the spawning contribution of young fish in that area.SíConsejo Superior de Investigaciones Científicas [https://ror.org/02gfc7t72]202320232003info:eu-repo/semantics/articlehttp://purl.org/coar/resource_type/c_6501http://hdl.handle.net/10261/325357reponame:DIGITAL.CSIC. Repositorio Institucional del CSICinstname:Consejo Superior de Investigaciones Científicas (CSIC)InglésCentro Oceanográfico de CádizSíinfo:eu-repo/semantics/openAccessoai:digital.csic.es:10261/3253572026-05-22T06:33:51Z
dc.title.none.fl_str_mv Changes in the distribution of sardine eggs and larvae off Portugal, 1985-2000
title Changes in the distribution of sardine eggs and larvae off Portugal, 1985-2000
spellingShingle Changes in the distribution of sardine eggs and larvae off Portugal, 1985-2000
Stratoudakis, Yorgos
Centro Oceanográfico de Cádiz
Pesquerías
title_short Changes in the distribution of sardine eggs and larvae off Portugal, 1985-2000
title_full Changes in the distribution of sardine eggs and larvae off Portugal, 1985-2000
title_fullStr Changes in the distribution of sardine eggs and larvae off Portugal, 1985-2000
title_full_unstemmed Changes in the distribution of sardine eggs and larvae off Portugal, 1985-2000
title_sort Changes in the distribution of sardine eggs and larvae off Portugal, 1985-2000
dc.creator.none.fl_str_mv Stratoudakis, Yorgos
Bernal, M.
Borchers, David
Borges, María de Fátima
Cardador, Fátima
author Stratoudakis, Yorgos
author_facet Stratoudakis, Yorgos
Bernal, M.
Borchers, David
Borges, María de Fátima
Cardador, Fátima
author_role author
author2 Bernal, M.
Borchers, David
Borges, María de Fátima
Cardador, Fátima
author2_role author
author
author
author
dc.contributor.none.fl_str_mv Consejo Superior de Investigaciones Científicas [https://ror.org/02gfc7t72]
dc.subject.none.fl_str_mv Centro Oceanográfico de Cádiz
Pesquerías
topic Centro Oceanográfico de Cádiz
Pesquerías
description Generalized additive models (GAMs) were fitted to sardine (Sardina pilchardus) egg distribution data from three daily egg production method surveys. The results showed that the area of egg cover off Portugal decreased significantly from 11 800 km2 in 1988 to 7000 km2 in 1997 and 7400 km2 in 1999. This is because of a significant reduction in sardine egg presence off northern Portugal, GAM estimated areas being similar or higher in the late 1990s for southwestern and southern Portugal. The distributional area covered by larvae was not estimated for 1988 (larval distribution extended beyond the survey area), although it was probably higher than the 9600 km2 for 1997 and 5500 km2 for 1999. In 1997 and 1999, the Gulf of Cadiz was also sampled, indicating extensive areas with sardine eggs and larvae (more than 50% of the total area of distribution off Portugal). Standardized data from 15 ichthyoplankton surveys between 1985 and 2000 show a decline in the mean probability of egg presence within the Portuguese continental shelf from the mid-1980s to the late-1990s, because of a marked reduction in egg presence off northern Portugal. Sardine larval data from the same surveys suggest that the reduction in mean probability of presence in the north is less marked than for eggs (although this comparison ignores the presence of sardine larvae beyond the continental shelf in the 1980s). Similar changes off northern Portugal and western Galicia are observed in commercial sardine catches and the acoustically estimated area of fish distribution. It is possible that the observed decline in spawning area off northwestern Iberia during the 1990s is indirectly reflecting the prevalence of environmental conditions detrimental to sardine recruitment (northerly winds during winter that favour coastal upwelling and offshore transport), which have reduced the spawning contribution of young fish in that area.
publishDate 2003
dc.date.none.fl_str_mv 2003
2023
2023
dc.type.none.fl_str_mv info:eu-repo/semantics/article
http://purl.org/coar/resource_type/c_6501
format article
dc.identifier.none.fl_str_mv http://hdl.handle.net/10261/325357
url http://hdl.handle.net/10261/325357
dc.language.none.fl_str_mv Inglés
language_invalid_str_mv Inglés
dc.relation.none.fl_str_mv Centro Oceanográfico de Cádiz
Sí
dc.rights.none.fl_str_mv info:eu-repo/semantics/openAccess
eu_rights_str_mv openAccess
dc.source.none.fl_str_mv reponame:DIGITAL.CSIC. Repositorio Institucional del CSIC
instname:Consejo Superior de Investigaciones Científicas (CSIC)
instname_str Consejo Superior de Investigaciones Científicas (CSIC)
reponame_str DIGITAL.CSIC. Repositorio Institucional del CSIC
collection DIGITAL.CSIC. Repositorio Institucional del CSIC
repository.name.fl_str_mv
repository.mail.fl_str_mv
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