ORIGINAL PAPER Diet of juvenile green turtles (Chelonia mydas) associating with artisanal fishing traps in a subtropical estuary in Brazil Shany Mayumi Nagaoka • Agnaldo Silva Martins • Robson Guimara ˜es dos Santos • Mo ˆnica Maria Pereira Tognella • Eurico Cabral de Oliveira Filho • Jeffrey A. Seminoff Received: 1 June 2011 / Accepted: 30 October 2011 / Published online: 23 November 2011 Ó Springer-Verlag 2011 Abstract The diet of 50 juvenile green turtles Chelonia mydas live-captured incidentally by fixed fishing traps between January and June 2009 in Canane ´ia Estuarine– Lagoon complex, Brazil, was studied through analysis of esophageal lavage samples. Green turtles consumed an omnivorous diet, with 18 food components identified and grouped into 4 categories as follows: terrestrial plants, algae, invertebrates, and seagrass. Black mangrove leaves were of the greatest importance to diet. Turtles incidentally get into fixed traps probably because these devices are located on mangrove margins, where they forage. The additional foods suggest that green turtles also feed opportunistically on material adhered to the trap structure and/or on items that cross into its interior. Green turtle diet in estuarine environments appears to be determined by the availability of food compo- nents, with some selectivity toward items of apparently greater nutritional value. Introduction The green turtle (Chelonia mydas) is threatened throughout its geographic range due to human overexploitation, inci- dental mortality related to fishing activities, and loss of feeding and nesting habitats (Limpus 1995).Understanding feeding habits of this endangered species is essential to its conservation, as diet directly influences growth rate, and in turn, reproductive output and demography (Balazs 1982; Bjorndal 1982). Green turtles have a particular life history in terms of its feeding ecology. As hatchlings inhabit oceanic areas and have an omnivorous diet (Bjorndal 1997); after pelagic phase lasting several or more years, they recruit to neritic habitats and shift toward a more herbivorous diet (Bjorndal 1997; Hirth 1997; Reich et al. 2007). It is known that green turtle’s diet is geographically variable, which makes it critical to conduct foraging studies in many feeding grounds, in order to generate biological information to facilitate site-specific management actions (Seminoff et al. 2002; Andre ´ et al. 2005; Lopez-Mendi- laharsu et al. 2005). The diet of green turtles may include algae (Ferreira 1968; Bjorndal et al. 1991) or seagrasses (Mortimer 1981; Moran and Bjorndal 2005) as primary constituents, but some populations may target both food resources (Garnett et al. 1985; Ross 1985, Brand–Gardner et al. 1999). In addition, green turtles in some areas consume large portions of invertebrates (Seminoff et al. 2002; Bugoni et al. 2003, Amorocho and Reina 2007). The differences in diet com- position are probably related to local availability of foods (Garnett et al. 1985), although some level of selectivity has been demonstrated (Bjorndal 1985; Brand–Gardner et al. 1999; Fuentes et al. 2006; Lopez-Mendilaharsu et al. 2005). Communicated by R. Lewison. S. M. Nagaoka (&)  A. S. Martins  R. G. dos Santos Departamento de Oceanografia e Ecologia, CCHN, Universidade Federal do Espı ´rito Santo, 29075-910 Vito ´ria, ES, Brazil e-mail: shanynagaoka@yahoo.com.br M. M. P. Tognella Departamento de Cie ˆncias da Sau ´de Biolo ´gica e Agra ´rias, CEUNES, Universidade Federal do Espı ´rito Santo, 29933-415 Sa ˜o Mateus, ES, Brazil E. C. de Oliveira Filho Departamento de Bota ˆnica, Universidade Federal de Santa Catarina, 88040-900 Floriano ´polis, SC, Brazil J. A. Seminoff Southwest Fisheries Science Center, National Marine Fisheries Service (NOAA), 3333 N. Torrey Pines Ct., La Jolla, CA 92037, USA 123 Mar Biol (2012) 159:573–581 DOI 10.1007/s00227-011-1836-y