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.

Better management of coastal marine resources generally requires good knowledge of habitats and resources. This need led to the performance of an identification and bioecological characterization study of critical sites for small pelagics in the Senegalese coastal marine zone. Biological and ecological data were collected using beach seines (12 to 28 mm mesh) and surface drifting gillnets (28 to 36 mm mesh) at sites identified by fishermen on the basis of surveys. The results of the study highlight the bioecological characteristics of these sites: (i) the Port-Baie Hann site - a nursery and spawning site with a high diversity for the target species; it is under marine pollution threat; (ii) the Mbodiène-Ngazobil site, with high diversity for target species and the Kafountine-Cap site are nursery and spawning sites under high fishing pressure, (iii) the Diakhanor-Sangomar site - a spawning site under the potential threat of exploration of offshore Sangomar oil in addition to the high fishing pressure. This work is a first flagship contribution to a process that should lead to the development and control of new tools for the effective and sustainable management of small pelagics at national and regional scales.

Senegalese and Mauritanian fisheries exploit the same species of white grouper but have different exploitation histories. In Senegal, white grouper has been fished for a very long time (since the 1970s), whereas it is relatively recent in Mauritania. In addition, Senegalese small-scale fishermen exploit this species in the Gambia. Nevertheless, mainly for practical reasons, all attempts to assess the status of the stock have, until recently, been conducted at a national level except by the FAO CECAF North working group who assumed it to be a single stock for the three countries. However, their analysis gives very little attention to length frequency data, even though the fisheries have different selectivity that are likely to affect exploitation rates. In addition, management is mainly focused on length, with no TACs or quotas established at national or sub-regional levels. This work is based on a large compilation of available data from the databases of three countries complemented by the collection of length frequencies data within the framework of the European Union Demerstem/PESCAO project. Two approaches were combined (catch and length-based model) to establish a reliable diagnosis of the state of this resource, along with a spatial analysis to identify the areas most affected by fishing. The results obtained for the sub-region show a severe overexploitation of biomass revealed by the Bayesian biomass production surplus model (JABBA). Stock status indicators show overfishing with low biomass (B/Bmsy = 0.34) and high fishing mortality (F/Fmsy = 5.79). Overall, the trajectory of the state of the stock illustrated by the Kobe figure indicates that the white grouper stock has been overexploited since the 1990s. Fishing pressure reached its highest levels during the recent period of 2016–2018 and these results are consistent when considering stock assessment at the national level. However, the length-based model (LBB) indicates a deterioration in average length, particularly in Senegal and the Gambia, especially since 2014. Adults, who migrate, are more abundant in Mauritania. Therefore, due to its high market value, white grouper is increasingly targeted, resulting in an unprecedented rise in fishing mortality over the past decade, particularly among larger individuals, with the most significant pressure observed in Senegal and the Gambia. Given that the stock spans three countries, a coordinated management approach at the stock level is essential. However, management measures must also be adapted to the specific status of the population within each country. Without such a concerted effort, this trend is likely to persist, further endangering the resource.