Feeding habits of Guiana dolphins, Sotalia guianensis, from south-eastern Brazil: new items and a knowledge review

Abstract

This study presents new information on feeding habits of Guiana dolphins, Sotalia guianensis, in south-eastern Brazil, together with new regression equations to evaluate the weight and length of fish from otoliths, showing an overview on the knowledge about this species' diet in this area. Eighteen stomach contents had been analysed and compared to 180 samples collected in another eight feeding studies. The analysed specimens were either incidentally caught in gillnets used in coastal waters by the fleet based in the Cananéia main harbour (25800 ′ S 47855 ′ W), south of São Paulo State, or found dead in inner waters of the Cananéia estuary between 2003 and 2009. Based on the index of relative importance analysis, the most important fish species were the banded croaker, Paralonchurus brasiliensis. Doryteuthis plei was the most representative cephalopod species. Stellifer rastrifer was the most important fish species observed in dolphins in inner estuarine waters and P. brasiliensis in recovered dolphins from coastal waters. Loliguncula brevis is the only cephalopod species reported from dolphins found in inner estuarine waters up to date. Doryteuthis plei was the most important cephalopod species observed in coastal dolphins. When considering other feeding studies, the most representative fish family in the diet of S. guianensis was Sciaenidae, which is mainly represented by demersal fishes. The main preys of S. guianensis are abundant in the studied areas, which may indicate an opportunistic feeding habit. The majority of them are not the most important target species by the commercial fishery in south-eastern Brazil.

Cadmium concentrations in Sotalia guianensis (Van Bénéden, 1864) in a tropical estuary, southeast of Brazil.

“…Lopes et al (2012) observed that the ingestion of Lolliguncula brevis was more representative for animals in inner estuary and Doryteuthis plei was more representative for coastal animals, both of Loliginidae family. However, studies have shown that not all cephalopods may be considered important vectors of the transfer of the metal to cetaceans in the Brazilian coast, mainly to differences in cadmium bioaccumulation capacity between different squid species due to environmental and physiological aspects.…”

Diet and foraging opportunism of the Guiana dolphin (Sotalia guianensis) in the Abrolhos Bank, Brazil

“…A yet unexplored possibility would be that sound‐producing gas bladders might be more reflexive to dolphin sonar. The importance of squid in the diet (see Lopes et al, ) is probably linked to the high energetic gain that would be provided by semelparous reproducing adults that are both highly nutritious and, often, gregarious.…”

Dolphins, Love and Enchantment: Tracing the Use of Cetacean Products in Brazil

“…Scholl et al indicated that, from the total of 21 love charm samples obtained in Belém, all were from S. guianensis, a salt water dwelling species. In contrast to botos, that inhabit continental waters, Guiana dolphins are found in shallow coastal waters, usually associated with mangroves and estuaries, where they feed on the most abundant schooling fish in the area (Lopes et al, 2012). Botos, on the other hand, are usually found in large river systems, where they feed on large fish (Best and da Silva, 1989).…”