Insight from PREFACE & AWA on Tropical Atlantic Tuna ecology and effects on western African fisheries economies

International audienc

International conference ICAWA 2016 : extended book of abstract : the AWA project : ecosystem approach to the management of fisheries and the marine environment in West African waters

Climate change will impact the coastal socio-ecosystems in various ways. This will be particularly true along the West African shores where no specific regional projection exercise has been carried out so far. We propose to present 1) the type of approaches that have been implemented for other coastal regions, e.g. in other upwelling systems to gain insight into the regional/local consequences of climate change; 2) the needs of regional stakeholders; 3) the scientific programs that could address these needs

Multifrequency acoustics measurements during the PIRATA FR25 cruise in the Eastern Tropical Atlantic Ocean

International Conference AWA (ICAWA), Dakar, SEN, 17-/11/2015 - 19/11/201

Regional consequences of climate changes on the West African coastal environment : identifying knowledge gaps [résumé]

ICAWA : International Conference AWA, Dakar, SEN, 13-/12/2016 - 15/12/2016Climate change will impact the coastal socio-ecosystems in various ways. This will be particularly true along the West African shores where no specific regional projection exercise has been carried out so far. We propose to present 1) the type of approaches that have been implemented for other coastal regions, e.g. in other upwelling systems to gain insight into the regional/local consequences of climate change; 2) the needs of regional stakeholders; 3) the scientific programs that could address these needs

Regional consequences of climate changes on the West African coastal environment : identifying knowledge gaps [résumé]

ICAWA : International Conference AWA, Dakar, SEN, 13-/12/2016 - 15/12/2016Climate change will impact the coastal socio-ecosystems in various ways. This will be particularly true along the West African shores where no specific regional projection exercise has been carried out so far. We propose to present 1) the type of approaches that have been implemented for other coastal regions, e.g. in other upwelling systems to gain insight into the regional/local consequences of climate change; 2) the needs of regional stakeholders; 3) the scientific programs that could address these needs

Simulations régionales de couplage de modèles physique-biogéochimique ROMS-PISCES sous serveur "Thredds", un produit d'exploration 3D

International Conference AWA (ICAWA), Dakar, SEN, 17-/11/2015 - 19/11/201

Analysis of zooplankton samples from AWA scientific research on board of R/V Thalassa 2014 using the zooscan approach [résumé]

ICAWA : International Conference AWA, Dakar, SEN, 13-/12/2016 - 15/12/2016Zooplankton organisms are crucial in nutrient cycling and energy transport, as they constitute the largest marine animal biomass and represent the main link between phytoplankton and other secondary consumers. Zooplankton is dominated by copepods and in many cases the Calanoids stand out by the number of species and/or biomass. In 2014 a scientific research was carried out along the coast of West Africa (Mauritania, Senegal and Gambia) on board of R/V Thalassa. Zooplankton samples were collected at day and night at 4 different stations along a coast-to-open ocean transect (station 1 inshore, station 4 offshore from R3) and 5 different depths using a multinet. Samples were analysed at the INDP laboratory using the zooscan approach. In short, the samples were fractionated into three size fractions (small 1000 micromètres) and imaged using a flatbed scanner. "Vignettes" small thumbnails and image characteristics of all objects were extracted from the image data with ZooProcess and sorted into 39 categories using Plankton Identifier and then manually validated. Copepods represented 91% of the total abundance; gelatinous organisms such as siphonophores, chaetognaths, salps and, appendicularians represented 5%; other crustaceans, such as euphausiids, ostracods, amphipods and decapods 2%; eggs and molluscs 1%. At the copepod level, calanoids were the most dominante group (total abundance percentage 88%), followed by cyclopoid and harpacticoid copepods (6%). Each oithonidae and eucalanidae families were (2%), oncaeaidae (1%) and nauplius copepods were 1%. In general, the total abundance of copepods differed spatially and along the water column. This may have to do with the biotic processes (e.g Chla) and abiotic (e.g the distance from the coast to the open ocean). The stations 1 and 2, the most inshore were those that presented greater abundances. The highest variations were observed 0 to 100m depth. The vertical distribution was used to detect migration patterns like diel vertical migration (DVM), which was mostly detected in the large fraction. For this fraction, the "normal" DVM (up at night and down during the day) was visible at stations 2 and 3, where the large copepods aggregated at the 25 to 50, and the 0 to 50 m depth level, respectively during nighttime. At station 1, large copepods were found to be almost homogeneously distributed in the water column during daytime, whereas they also aggregated at the 25 to 50 m depth layer during nighttime. Further analysis of the data is ongoing and will resolve particulate and dissolved matter fluxes related to these migrations, but also can inform ecosystem modelling efforts

Optimal fishing agreement between neighboring countries sharing a common migratory fish population [résumé]

ICAWA : International Conference AWA, Dakar, SEN, 13-/12/2016 - 15/12/2016A mathematical model is developed to represent an idealized system of a shared fish stock associated with different exclusive economic zones. We apply such model on small pelagic fisheries shared between Southern Morocco, Mauritania and the Senegambia. The complete model is a set of six ordinary differential equations describing the time evolution of the fish biomass and the fishing effort in the three zones. The fish species targeted as small pelagics could be consid- ered to perform quick displacement between the different zones, in comparison to their growth and harvesting. We take advantage of the two time scales to obtain a reduced model governing the total fish biomass of the system and fishing efforts in each zone. We study existence and stability of equilibrium points of the reduced model. The simulations show that as a result of competition between fisheries per zone there can only be one winner in the general case. Nevertheless there is also an arising case that allows an operational management of shared fisheries by acting on the cost of fishing unit effort, indeed we found that a large number of equilibrium exist. From this last case the initial distribution of fishing effort strongly impact the optimal equilibrium that can be reached. Lastly the model report that the country with the highest carrying capacity density may get less landings when collaborating with other countries than if it minimise its fishing costs. Such findings should allows regional fisheries organizations to get potential new ways for neighbouring fish stock management plan