CEPHALOPODS IN THE TROPHIC RELATIONS OFF SOUTHERN BRAZIL

摘要

Trophic relations of cephalopods in southern Brazil were investigated from predation on cephalopods by 71 species of potential predators, including two squids, 47 fishes, seven seabirds and 15 marine mammals from shelf, upper slope and oceanic adjacent waters. In all, 27 families and 41 species of cephalopods were identified from stomach contents. The number of families ranged from six, in the diet of shelf predators, to 27 families in those from upper slope and adjacent oceanic waters. The most frequent cepha-lopod prey on the shelf was Loligo sanpaulensis, particularly important in the diet of Franciscana dolphin Pontoporia blainvillei, occurring also in the diet of the penguin Spheniscus magellanicus, the fur seals Arctocephalus australis, A. gaze/la, A. tropicalis, and several benthic and demersal fishes. Ommastrephidae, mainly Illex drgentinus and Ornithoteuthis antillarum, was the most frequent family in the diet of predators from upper slope and adjacent oceanic waters. Illex argentinus was an important prey for the wreckfish Polyprion americanus, the bigeye tuna Thunnus obesus, the swordfish Xiphias gladius and some marine mammals, especially in their winter and spring northward reproductive migration. Ornithoteuthis antillarum was frequent in the diet of the skipjack tuna Katsuwonuspelamis, the albacore Thunnus alalunga, the yellowfin tuna T. albacares, the Atlantic sailfish Istiophorus albicans and the white marlin Tetrapturus albidus. Am-moniacal squids, such as Ancistrocheirus lesueurii, Histioteuthis xpp, Chiroteuthis veranii and Octopoteuthis sp, were mainly found in stomach contents of the blue shark, Prionace glauca, the pygmy sperm whale Kogia breviceps, the dwarf sperm whale K. sima, the long-finned pilot whale, Globicephala melas and oceanic seabirds. The relative importance, based on frequency of occurrence, of cephalopods as food resources seems to be higher in the food chains of the upper slope and adjacent oceanic waters, when compared to the continental shelf.