Book of Abstracts submitted to the IV Congress of Marine Sciences

Sardinella aurita, or round sardinella, has been the main small pelagic fish species harvested off Senegal and Mauritania coasts over the last 4 decades and plays a central role for sub-regional food security and economic incomes. The landings of this species have strongly declined recently. Intense exploitation and climate change are acting together but population&#8217;s dynamics are too poorly understood to disantangle the different drivers and to clearly evaluate the current state of S. aurita&#8217;s population. In the present study, we developed a bio-physical, individual based model for S. aurita population off North-West Africa. The hydrodynamic environment was simulated by a regional model ("ROMS") configuration covering the area 5°-40°N and 5°-30°W, with a 8km resolution and 32 sigma-levels in our area of interest. The biogeochemical compartments were simulated using the PISCES model coupled with ROMS. Fish schools of S. aurita were represented by active lagrangian markers affected with ad hoc larval, juvenile and adult fish swimming behavior. Individual&#8217;s physiology was described following the local temperature and food availability by the Dynamic Energy Budget model "DEB". The extended kinesis algorithm ruled the horizontal fish movement and depends on food research, individual temperature preference and spawning migration, whereas fish vertical position in the water column was set for each stage according to scientific knowledge. We investigate the predicted seasonal migrations pattern of S. aurita off West Africa over the period 1980-2006. Then we also evaluate the fluctuations of fish biomass available for coastal fisheries (h<200m) in 4 distinct areas from the western Saharan bank (24°N) down to the Bijagos islands (11°N) and compare with the available fish landings data on this period. Finally, we calculate seasonal connectivity indices between the populations in the 4 areas selected as the percentage of fish present in an area that was born in another area

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

Mesoscale physical processes can affect the fate and distribution of fish eggs and larvae by aggregating and retaining them in favorable habitats or spreading them away to inappropriate areas. Here we examined the effect of fine scale processes on fish larval retention through a biophysical model of the early life stages of Sardinella aurita taken as an example within the Senegalese upwelling region. A set of 3 ROMS configurations is used from coarser (~ 9km, 7.5km) to finer (~ 2km) resolution. The ICHTHYOP individual based model is then forced by the different model experiments. To take into account more realistic physical forcing, the finer resolution configuration was used to test the effect of synoptic winds and tides. We first show that a finer resolution of physical processes provides a retention twice stronger. In addition that experiment shows 2 contrasted results in the region which differ from previous modelling work : 1) the northern domain considered so far as a low retention area displays high retention values and 2) a better resolution of the hydrodynamic of the Senegalese shelf modifies significantly the retention spatial patterns in the southern area although the seasonality remains similar. Simulation using synoptic winds and tidal forcing suggest a reduction of retention induced by a higher larval mortality due to enhanced export transport and stronger lethal temperature exposure

Observations of plankton communities in the Senegalese upwelling system

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

Observations of plankton communities in the Senegalese upwelling system

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

An individual based biophysical model to study Sardinella aurita population's spatial dynamic off North-West Africa [résumé]

International Conference AWA (ICAWA), Dakar, SEN, 09-/12/2014 - 11/12/201

An individual based biophysical model to study Sardinella aurita population's spatial dynamic off North-West Africa [résumé]

International Conference AWA (ICAWA), Dakar, SEN, 09-/12/2014 - 11/12/201

New insights on the spatial structure of the main small pelagic fish population (Sardinella aurita) in the Canary Upwelling System using an individual based biophysical model

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

New insights on the spatial structure of the main small pelagic fish population (Sardinella aurita) in the Canary Upwelling System using an individual based biophysical model

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

Toward new scenario on small pelagic fish spatial population dynamics related on both hydrodynamic and biogeochemical simulations

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