Effect of environmental conditions on the seasonal and inter‐annual variability of small pelagic fish abundance off North‐West Africa: The case of both Senegalese sardinella |
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| Authors: | Modou Thiaw Pierre‐Amaël Auger Fambaye Ngom Timothée Brochier Saliou Faye Ousmane Diankha Patrice Brehmer |
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| Affiliation: | 1. Centre de Recherches Océanographiques de Dakar‐Thiaroye (CRODT), Institut Sénégalais de Recherches agricoles (ISRA), Dakar, Sénégal;2. Laboratoire de l'Environnement Marin (UMR 195 Lemar), Technop?le Brest Iroise, Institut de Recherche pour le Développement (IRD), Plouzané, France;3. Instituto Milenio de Oceanografia and Escuela de Ciencias del Mar, Pontificia Universidad Catolica de Valparaiso, Valparaiso, Chile;4. Laboratoire de l'Environnement Marin (UMR 195 Lemar), Institut de Recherche pour le Développement (IRD), Hann, Dakar, Sénégal;5. Institut de Recherche pour le Développement (IRD), UMI 209 UMMISCO, Univ. Paris 06, Sorbonne Universités, Bondy, France;6. Laboratoire de Physique de l'Atmosphère et de l'Océan Siméon Fongang (LPAO‐SF/ESP), Université Cheikh Anta Diop de Dakar (UCAD), Dakar, Fann, Sénégal |
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| Abstract: | The objective of this study was to assess the effect of environmental variations on the abundance of Sardinella aurita and Sardinella maderensis in Senegalese waters in the upwelling system. Monthly data indicating the abundance of sardinella were first estimated from commercial statistics, using Generalized Linear Model from 1966 to 2011. Abundance indices (AIs) were then compared with environmental indices, at the local scale, a Coastal Upwelling Index (CUI) and a coastal Sea Surface Temperature (SST) index, and on a large scale, the North Atlantic Oscillation (NAO), the Atlantic Multidecadal Oscillation (AMO) and the Multivariate El Niño Southern Oscillation Index (MEI), using correlations and times series analyses. The results showed that the abundance of sardinella is determined by a strong seasonal pattern and inter‐annual fluctuations. The abundance of S. aurita peaked in spring and in autumn, whereas that of S. maderensis peaked in the warm season (July–September). The trend of the sardinella abundance was significantly correlated with the CUI, especially in autumn and spring. Interannual fluctuations of S. maderensis and S. aurita abundance are, respectively, driven by the precocity and the duration of the upwelling season that is attributed to distinct migration patterns. Both sardinella species also respond with a delay of around 4 years to the winter NAO index and the autumn CUI, and the AMO index, respectively, both related to migration patterns. The wide variations in sardinella biomass are caused by variations in environmental conditions, which should be considered in the implementation of an ecosystem‐based approach in sardinella stocks management. |
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| Keywords: | Climatic change oceanography
Sardinella aurita
Sardinella maderensis
small pelagic small‐scale fisheries |
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