Diets of marine mammals stranded on the northwestern Spanish Atlantic coast with special reference to Cephalopoda

Abstract

Stomach contents from 59 marine mammals, 28 Delphinus delphis, 14 Tursiops truncatus, three Grampus griseus, four Stenella coeruleoalba, three Globicephala melas, one Ziphius cavirostris, four Phocoena phocoena, one Physeter macrocephalus and one Balaenoptera acutorostrata stranded on the northwestern Spanish Atlantic coast from December 1990 to March 1993 were examined. A total of 9076 fish otoliths and 654 cephalopod upper and lower beaks were collected. The otoliths were identified only to family level, representing by number 65% Gadidae, 24% Gobiidae, 6% Atherinidae, 2% Ammodytidae, 1.5% Clupeidae and the rest Carangidae, Labridae, Argentinidae, Macroramphosidae and Bothidae. The cephalopod beaks belonged to 12 species of nine families. The cephalopod families contributing food of these marine mammals, in order of contribution by number of specimens are, the Loliginidae (56.9%), the Octopodidae (25.3%), the Ommastrephidae (11.9%), the Sepiolidae (2.4%), the Histioteuthidae (0.9%), the Chiroteuthidae (0.9%), the Cranchiidae (0.8%), the Mastigoteuthidae (0.3%) and the Gonatidae (0.15%). The great part of the cephalopods observed in the stomach contents were small in size, except for some octopods in Grampus griseus and Globicephala melas, and Mastigoteuthis sp. in Physeter macrocephalus. The results indicated that D. delphis, T. truncatus and Phocoena phocoena are primarily fish-eating, while Grampus griseus, Globicephala melas and Physeter macrocephalus had only cephalopod remains in their stomachs.