J. Mar. Biol. Ass. U.K. (2007), 87, 253–254 Printed in the United Kingdom Journal of the Marine Biological Association of the United Kingdom (2007) doi: 10.1017/S0025315407053647 Stomach contents of the marine tucuxi dolphin (Sotalia guianensis) from Rio de Janeiro, south-eastern Brazil The tucuxi dolphin (genus Sotalia, Gray 1866; Cetacea, Delphinidae) is distributed along the coasts of central and South America, including the basins of the Amazon and Orinoco rivers (Borobia et al., 1991). The marine tucuxi dolphin (S. guianensis) inhabits coastal and estuarine waters from Honduras (14°N) to southern Brazil (27°S) (Da Silva & Best, 1996). Despite its continuous occurrence along the distributional range, there are few studies reporting on its feeding habits (Borobia & Barros, 1989; Santos et al., 2002; Di Beneditto & Ramos, 2004). This note presents new information about the feeding habits of the marine tucuxi dolphin in south-eastern Brazil, where this species is one of the most vulnerable cetaceans due to its coastal habitat and involvement in gill-net fisheries. During regular beach surveys along the central coast of Rio de Janeiro State (22°25'S–23°00'S) (Figure 1) between 1999 and 2005, we recorded 29 carcasses of the marine tucuxi dolphins and collected the stomach contents from ten specimens to investigate their feeding habits (Table 1). Teleosts otoliths, fish bones and squid beaks were used to identify, quantify and estimate the length and weight of the prey species. For each stomach, the maximum number of either left or right otoliths and upper or lower beaks, was used as an indication of the total number of fish and squid prey items, respectively. The index of relative importance (IRI) (Pinkas et al., 1971) was calculated to determine the representative prey species. Teleosts and cephalopods were considered as independent prey in order to reduce under- or over-estimation of their importance. At least 17 fish species (128 individuals and 8200.1 g) and two squid species (five individuals and 559.6 g) were identified in the stomach contents (Table 2). These species live in coastal habitats and are abundant all year round in the study area (Haimovici et al., 1989; Di Beneditto & Lima, 2003). In general, they have low commercial value or are considered as by-catch in the local fisheries (Di Beneditto et al., 1998). Ana Paula Madeira Di Beneditto* ‡ and Salvatore Siciliano † *Universidade Estadual do Norte Fluminense, CBB, Laboratório de Ciências Ambientais, Avenida Alberto Lamego, 2000, Campos, RJ, 28013-602, Brazil. † Grupo de Estudos de Mamíferos Marinhos da Região dos Lagos-GEMM-Lagos, Escola Nacional de Saúde Pública/FIOCRUZ, Departamento de Endemias Samuel Pessoa, Rua Leopoldo Bulhões, 1480, Manguinhos, Rio de Janeiro, RJ, 21041-210, Brazil. ‡ Corresponding author, e-mail: anapaula@uenf.br Figure 1. Rio de Janeiro State, south-eastern Brazil, indicating the study area. Field code Collection date Total length (cm) Sex GEMM 021 20 July 2001 190.0 Male GEMM 034 23 August 2002 153.0 Female GEMM 038 05 November 2002 178.0 – GEMM 039 09 November 2002 191.0 Female GEMM 041 23 November 2002 167.0 Male GEMM 048 05 November 2003 182.0 Male GEMM 050 05 November 2003 186.0 Female GEMM 065 02 September 2004 173.0 Female GEMM 076 11 December 2004 160.0 – GEMM 087 03 September 2005 184.0 Male GEMM, Grupo de Estudos de Mamíferos Marinhos da Região dos Lagos. Table 1. Biological data on the marine tucuxi specimens stranded along the central coast of Rio de Janeiro State, south-eastern Brazil. Along the central coast of Rio de Janeiro State (22°25'S–23°00'S), south-eastern Brazil, the marine tucuxi dolphin (Sotalia guianensis) feeds on neritic prey that are distributed through the water column and are abundant all year round. The most frequently found species were the teleost fish Trichiurus lepturus, Cynoscion guatucupa, Isopisthus parvipinnis and Porichthys porossisimus. Fish species were more important than cephalopod species in the diet of the marine tucuxi. Back calculations of prey sizes indicated that they feed mainly on young specimens. The present study provided additional information on the feeding habits of the marine tucuxi dolphin.