The Diet of the White-Breasted CormorantPhalacrocorax carbo lucidusAlong the Atlantic Coast of West Africa

Abstract

The White-breasted Cormorant Phalacrocorax carbo lucidus occurs in Central, West, East and South Africa. The West African population breeds on the Cape Verde Islands and along the Atlantic coast from Mauritania to Guinea. The species forages in marine, brackish and fresh waters and is thought to be (almost) completely piscivorous. However, data on diet are poorly available and completely lacking for the West African population. We collected regurgitated pellets at three sites, in Mauritania (Island of Zira, Banc d'Arguin) and Senegal (Ilot aux Oiseaux, a small islet in the estuary of the Senegal River and Ile de la Madeleine near Dakar). On the basis of otoliths, 34 fish species belonging to 21 families were identified. There was great variation in the diet of the cormorants at the different sites, with Haemulidae and Batrachoididae being dominant on Ile de la Madeleine, Ariidae and Cynoglossidae on Ilot aux Oiseaux and Sparidae, Mugilidae and Batrachoididae on the Island of Zira. Most fish consumed were coastal species, many of which may also enter brackish or fresh waters. The cormorants mainly ate benthic and bentho-pelagic fish species varying in size between 10 and 20 cm. There was great variation in the number of otoliths per pellet at the different sites with a remarkably small number in the Zira sample. We investigated whether a small number of otoliths per pellet can be explained by the prey fish being larger or by the otoliths being more eroded. The latter might be an indication that part of the otoliths had been totally dissolved and thus disappeared from the samples. Neither fish size nor extent of wear could explain the small number of otoliths in the Zira sample. A comparison between artisanal fisheries catches and the diet of the cormorants showed hardly any overlap for the Senegalese sites. However, substantial overlap was found at the Banc d'Arguin in Mauritania. These differences can be explained by the high proportion of pelagic species caught in the Senegalese sites.