Population variance in prey and macronutrient selection of an endangered marine mammal, the franciscana dolphin

PASO VIOLA, MN; BLASINA, G; POLIZZI, P; RODRIGUEZ, D; DENUNCIO, P; RAUBENHEIMER, D; MACHADO, R; MACHOVSKY CAPUSKA, G; CAPPOZZO, HL; GIARDINO, G; GERPE, M

Valparaiso

Congreso; XVII Reunión de Trabajo de Especialistas de Mamíferos Acuáticos de América del Sur (RT); 2016

SOLAMAC

Disentangling the intricacies governing prey selection and dietary breadth in wild predators are important for understanding their role in structuring ecological communities and provides critical information for the management and conservation of ecologically threatened species. Here, we combined dietary analysis, nutritional composition analysis of prey, literature data and nutritional geometry (right-angled mixture triangle models -RMT-) in the most threatened small cetacean in the western South Atlantic Ocean, the franciscana dolphin (Pontoporia blainvillei). Our results demonstrate that franciscanas inhabiting the fourth franciscana management area (FMA IV) used different nutritional mechanisms to adjust their nutritional intake in spite of living in three different nutritional niches: estuarine, north marine and south marine. Using literature data and RMT models we also have found that franciscanas from Rio Grande do Sul (FMA III) have similar macronutrient compositions in the diets than marine franciscanas from the IV FMA, whereas northernmost franciscanas (Sao Paulo, FMA II and Rio de Janeiro, FMA I) achieve their nutritional intake through different mechanisms. These findings support previous suggestions on the presence of three populations within the FMA IV management unit and are vital to interpret the impact of coastal fisheries on this species. It is crucial to better comprehend food selection and dietary needs of the different franciscana populations to enhance the current management and format of four FMAs to protect this endangered marine predator.