No 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.

No abstract

No abstract

Demersal shrimp fisheries, which are not very selective, generate significant discards and / or bycatch, generally composed of crustaceans, fish and molluscs of different size classes. As part of the implementation of the management plan for the deepwater shrimp Parapenaeus longirostris in Senegal, selectivity tests of the Nordmore device were conducted. Thus, three Nordmore grids characterized by different spacings between the bars (24, 28 and 30 mm) were tested on the experimental trawl in the Senegalese Economic Zone. Regardless of spacing, the Nordmore Grid completely removed large individuals from several species of commercial interest (John dory and Bearded brotula) or not (rays, sharks, etc.). Gamba shrimp loss analyzes indicate a significant difference (α <0.05) between the three spacer grids 24, 28 and 30 mm. Regardless of the type of grid, the amount of shrimp sorted per minute is larger for the experimental trawl; and this quantity increases with the spacing of the grid. The 30mm grid stands out with percentages of gamba shrimp losses ranging from 3 to 20% with an average of 8%; and a ratio of bycatch / gamba shrimp catch around 2.2 / 1, below the world average for this type of fishery (5/1).

Senegal is in a very favourable geographical position for sea fishing. Its coast has an upwelling favouring a good development of phytoplankton very appreciated by the various fish families that populate its Exclusive Economic Zone (EEZ). The little pelagic fish make up the majority of landings. The dynamics of this family of resources is very complex while its perfect mastery is essential for a fishing well controlled maritime. The mathematical models that exist in the literature have not address the different issues related to maritime fisheries and climate change in the Senegalese fishing areas. The linear programming model in integer numbers has been developed after calculation of equilibrium biomass, catches at equilibrium catchability by the application of Schaefer and Freon models in the  Senegalese Economic Exclusive Zone. Two proposals have been developed to better explain the tools used in the writing of the mathematical model. The simulation results were led to the design of a linear integer Program (PLNE). The objective is to maximize the biomass of this family of fish resources on the Petite C\^ote, Grande C\^ote and Cape Verde depending on samples and climate change. In the application of the model, real data made it possible to test the Linear program in integer numbers obtained. This optimization study allowed us to find an effective way to maximize recruitment within this resource family. This consists in setting up several less expensive marine refuges to build in the fishing zones targeted by the study. The simulation computer program of the model is presented in the appendix.

No abstract

No abstract