Information on the biological parameters of exploited fish stocks facilitates the objective assessment and management of these living resources. The sardine (Sardina pilchardus) is considered as overexploited in northwest Africa. It is a key species of the Canaries current large marine ecosystem (CCLME) of the Atlantic Ocean due to its socioeconomic importance, as well as being a key intermediary species in marine food web. A massive decline in caught fish for Senegal over half a century is also reported (61,648 t in 1994 to 7486 t in 2017). Here, we analyzed the age and growth parameters of sardines in the Exclusive Economic Zone of northern Senegal. Maximum body size was 31 cm total length (TL). A growth performance index (φ′) and a growth rate coefficient (K) of 2.65 and 0.85, respectively, were determined, with this being the first record for this country. Sardines had higher asymptotic length (L_∞, 30.5 cm TL) and age (6 years) in northern Senegal compared with Morocco (Atlantic Ocean) and the Mediterranean Sea. The asymptotic length found in Northern Senegal was also higher than in other part of the CCLME and Mediterranean Sea. This difference might be attributed to differences in the pelagic habitat, environmental factors, and/or fishing pressure. This study provides new insights towards establishing management measures, especially in data-poor fisheries and should act as an advocacy to increase sub-regional collaborations.

Small pelagic fishes play important ecological roles in marine ecosystems, constitute some of the most economically valuable fisheries resources, and play a vital role in West African food security. Often living in upwelling regions, these species appear to have developed mechanisms to cope with environmental variability, such as opportunistic reproductive tactics, enhancing their growth performance, or increasing their egg production by following the more predictable system attributes of seasonal cycles. To test this hypothesis, we investigated size-dependent patterns of the two growth mechanisms (i.e., growth rate) of two West African small pelagic populations (Ethmalosa fimbriata and Sardinella maderensis) in upwelling environments. These results were discussed with other areas in African tropical Atlantic waters. The monthly mean length of both species showed a large variation over the study period. Based on the fish length-frequency data and a coastal upwelling index, we found that the growth peaks of the species tended to occur during the most intense periods of upwelling (March–April). This study showed a significant decrease in size compared with other species found in other regions. It demonstrates how the geographical distribution of the same species, together with location-specific variation in temperature and food, can combine to determine local and regional growth responses in pelagic fish. Changes in growth rate may be an adaptive tactic in response to environmental change, as well as phenotypic plasticity in fish. This knowledge is essential to predict future changes in fish productivity and distribution vs. climate and to provide effective advice for ecosystem-based 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.