Long-term fishing impact on the Senegalese coastal demersal resources: diagnosing from stock assessment models

Abstract

For the first time in Senegal, assessments based on both stochastic and deterministic production models were used to draw a global diagnosis of the fishing impact on coastal demersal stocks. Based one national fisheries databases and scientific trawl surveys data: (i) trends in landings since 1971 were examined, (ii) abundance indices of 10 stocks were estimated using linear models fitted to surveys data and commercial catch per unit efforts, and (iii) stock assessments were carried out using pseudo-equilibrium Fox and Pella-Tomlinson models and a Biomass dynamic production model fitted in a Bayesian framework to abundance indices. Most stocks have seen their abundance sharply declining over time. All stocks combined, results of stock assessments suggest a 63% reduction compared to virgin state. Three fifth of demersal stocks are overexploited and excess in fishing effort was estimated until 75% for the worst case. We conclude by suggesting that the fishing of such species must be regulated and an ecosystem approach to fisheries management should be implemented in order to monitor the whole ecosystem.

Successful artificial reefs depend on getting the context right due to complex socio-bio-economic interactions

“…Specifically, in the context of generalized overfishing in Senegal 21 , deciding not to fish on the AR represents significant individual loss, despite being recognized as beneficial, globally 22 . It has been argued that this situation would rarely occur in small-scale fisheries, due to existing arrangements between individuals 23 .…”

Length-based assessment of five small pelagic fishes in the Senegalese artisanal fisheries

“…In the long term, this fact could prevent the sustainability of small pelagic stocks because it does not allow them to renew themselves properly. Indeed, sardinella species show spatial and temporal distribution patterns by size group [4,5]. Indicators based on length frequencies can be used to establish fisheries management measures [19,48].…”

“…It's also the main resource for traditional processing activities (drying or smoking) and plays a vital role in the diet of population [3]. However, with poorly adapted and ineffective fisheries management policies, this sector is confronted with the effects of overfishing and the collapse of fisheries in terms of local consumption, food security, and economic value [2,4,5]. Attempts to regulate fisheries in the region through the establishment of marine protected areas and gear restrictions have been limited by the lack of scientific data and inadequate infrastructure and human capacity to effectively monitor and assess marine resources [5,6].…”

Sr Isotope Ratios (87Sr/86Sr) in Water and Fish Otoliths as Estuarine Salinity Tracers: Case Studies from Three NW African Rivers

“…Juvenile and adult C. parkii move relatively freely through estuaries and are found as far as ~190 km upstream in the Gambia River (Laë et al 2004), while salinities exceeding 50 restrict their presence to the lower ~ 30 km of the adjacent Sine-Saloum (Panfili et al 2006;Simier et al 2021). Along with other Ariidae, C. parkii form a major component of fisheries along the Senegalese and Gambian coast (Ba et al 2018;Laë et al 2004), while also highly impacted by bycatch (e.g., Castro et al 2013). C. nigrodigitatus are of freshwater origin and common to most western African basins, primarily inhabiting the shallow waters of lakes, rivers and swamps.…”