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XIV Reunião de Trabalho de Especialistas em Mamíferos Aquáticos da América do Sul (RT)
8º Congresso da Sociedade Latinoamericana de Especialistas em Mamíferos Aquáticos (SOLAMAC)
Florianópolis (SC), 24 a 28 de outubro de 2010
TROPHIC RELATIONSHIP BETWEEN GUIANA DOLPHIN AND ITS PREY SPECIES FROM SEPETIBA
BAY, RIO DE JANEIRO STATE, BRAZIL
Bisi, T. L.1,2,3; Lailson-Brito, J.3; Lepoint, G.4; Azevedo, A. F.3; Dorneles, P. R.2; Flach, L.5; Malm, O.2;
Das, K.4
1
Programa de Pós-Graduação em Ecologia (PPGE), Universidade Federal do Rio de Janeiro (UFRJ), Rio
de Janeiro, Brasil. [email protected]
2
Laboratório de Radioisótopos, Instituto de Biofísica, Universidade Federal do Rio de Janeiro (UFRJ), Rio
de Janeiro, Brasil
3
Laboratório de Mamíferos Aquáticos e Bioindicadores "Profa. Izabel Gurgel" (MAQUA), Faculdade de
Oceanografia, Universidade do Estado do Rio de Janeiro (UERJ), Rio de Janeiro, Brasil
4
Centre MARE, Laboratoire d’Oceanologie, Université de Liége, Belgique
5
Projeto Boto-Cinza, Mangaratiba, Brasil
This study investigated the trophic relationships among organisms from Sepetiba Bay (Rio de Janeiro,
Brazil). The investigation was carried out through determination of carbon and nitrogen stable isotopes in
muscle of Guiana dolphin (Sotalia guianensis) (n=44), 21 fish species (n=119), one cephalopod species
(n=10) and two crustacean species (n=15). Stable isotope measurements were performed on a V.G. Optima
(Micromass) IR-MS coupled to an N-C-S elemental analyzer (Carlo Erba). Mean δ13C and δ15N values varied
significantly among the species (ANOVA F6,137= 16.26 and F6,137= 75.74, respectively; p<0.00001).
Concerning δ13C values, the multiple comparisons test showed that the difference was only significant in
detritivorous species and in cephalopods species (Tukey HSD test, p<0.001). The detritivorous fishes Mugil
curema (-9.4‰) and Mugil liza (-13.9‰) were notably more 13C enriched than expected. This finding may be
explained by the presence of some 13C enriched macroalgae in their diet. The lowest average δ15N values
occurred in detritivorous species (9.4‰). Intermediate mean δ15N values were observed in planctivorous
fishes (13.8‰), in benthic invertebrate feeder fishes (14.1‰) and in cephalopods (14.4‰). The highest
mean δ15N values occurred in benthic invertebrates and fish feeders (15.6‰), as well as in those species of
demerso-pelagic feeding habit (15.9‰) (Tukey HSD test, p<0.01). It was expected that Guiana dolphin
presented the highest trophic level, but the average δ15N value (14.07‰) was smaller than those of most fish
species. The main preys found in Guiana dolphin stomach contents in Sepetiba Bay are Micropogonias
furnieri (benthic invertebrate feeder) and Centengraulis edentulus (planctivorous fish). In fact, the δ15N
results showed that Guiana dolphin feeds on organisms occupy relatively low trophic levels, such as
planktivorous fishes and invertebrate feeders. Additionally, the result suggests that not all the ingested
species are in fact important in the diet of Guiana dolphins from Sepetiba Bay. Stable-carbon isotope values
varied greatly among individual dolphins, ranging from -17.16‰ to -12.80‰. The results suggest variable
dietary resources, as well as that the species uses adjacent areas to forage rather than feeding exclusively
inside Sepetiba Bay.
Keywords: tropical estuary, stable isotope, Sotalia guianensis
Financial support: CAPES (fellowship), “Pensa Rio” Program/FAPERJ (Proc. E-26/110.371/2007), APQ12009/1 - FAPERJ (Proc. E26-110.858-2009), Universal/CNPq (480701/2009-1) and Cetacean Society
International grant.
Sociedade Latinoamericana de Especialistas em Mamíferos Aquáticos – SOLAMAC