Horizontal distribution of dominant pelagic fish eggs in West African waters

Early life stages of dominant West African pelagic fishes, most of which are commercially important, are rarely studied especially in Senegalese and Mauritanian coastal waters. The aim of the present study was to examine the horizontal distribution of pelagic fish eggs of European sardine (Sardina pilchardus), anchovy (Engraulis encrasicolus), round sardinella (Sardinella aurita) and horse mackerel (Trachurus trachurus) in winter-spring and summer. The two seasons revealed two contrasting environmental conditions. While in late winter strong upwelling shaped the environmental conditions, in summer a warm tropical influx of surface water from Senegal towards Mauritania was observed. Fish eggs occurred in both seasons along the shelf coasts of Mauritania and Senegal. The distribution of fish eggs was related to temperature, salinity and chlorophyll data obtained at each sampling position. Eggs of most species were concentrated in coastal waters off the Banc d'Arguin, in Saint-Louis and along the Senegalese sub-region. Spawning occurs mainly during winter and would be linked to environmental changes in particular temperature that significantly vary eggs distribution as notified with Sardina pilchardus and Sardinella aurita during late winter. Moreover, results have shown a significant role of other habitat factors such as chlorophyll, depth and also the continental shelf-break, as a mechanism of retention of fish eggs.