Cephalopods in the diet of marine mammals stranded or incidentally caught along southeastern and soutehrn Brazil (21-34 S)

Abstract

Cephalopod remains found in 286 stomach contents of 13 species of odontocetes (Pontoporia blainvillei, Lagenodelphis hosei, Sotalia fluviatilis, Stenella frontalis, Steno bredanensis, Tursiops truncatus, Delphinus sp., Globicephala melas, Orcinus orca, Pseudorca crassidens, Kogia breviceps, K. sima and Physeter macrocephalus) four species of pinnipeds (Arctocephalus australis, A. gazella, A. tropicalis and Mirounga leonina) were identified and measured. The stomachs were collected from stranded or incidentally caught marine mammals from Rio de Janeiro to Paraná states (21–26°S) and Rio Grande do Sul (29–34°S), between 1985 and 1998. Twenty-five species of 16 families of cephalopods were identified. Cephalopod prey were small to medium sized. The diversity of cephalopods as prey was lower for coastal marine mammals and increased in offshore species that fed on diverse oegopsin squids including both the fast moving muscular squids and the less mobile neutrally buoyant cephalopods. In common dolphins, ommastrephid and loliginid squids and the sepiolid Semirossia tenera, were all important in the diet. Loliginid squids were the most frequent cephalopod in the diet of six other species of dolphins and three species of fur seals. Loligo sanpaulensis was recorded in specimens from throughout the study area, whilst Loligo plei and Lolliguncula brevis were frequent in the northern area. Benthic octopuses were found only in the diet of bottlenose dolphin and franciscana. Pelagic octopuses, particularly Argonauta nodosa, were only relatively frequent in the stomach contents of franciscana. In the stomach contents of larger odontocetes, as well as in Southern elephant seals and SubAntarctic fur seals, squids of the families Ancistrocheiridae, Chiroteuthidae, Cranchiidae, Enoploteuthidae, Histioteuthidae, Lycoteuthidae, Octopoteuthidae, Onychoteuthidae and especially Ommastrephidae were found.