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Data from: Geographical and intrapopulation variation in the diet of a threatened marine predator, Pontoporia blainvillei (Cetacea)

Citation

Henning, Barbara et al. (2017), Data from: Geographical and intrapopulation variation in the diet of a threatened marine predator, Pontoporia blainvillei (Cetacea), Dryad, Dataset, https://doi.org/10.5061/dryad.5415m

Abstract

Diet variation can occur in geographically structured populations due to variation in prey availability. Within locations, diet may vary due to effects of season, sex, age, and individual. Nevertheless, these sources of variation are seldom considered together in dietary studies. Major efforts are underway to investigate population and ecological traits of marine organisms to set guidelines for conservation and management. Examining diet variation is a major concern when developing conservation guidelines for threatened species, especially for marine predators whose prey availability can be reduced by commercial fisheries. We analyzed diet variation at the geographical and intrapopulation levels for detecting stocks of the franciscana dolphin (Pontoporia blainvillei) within São Paulo State coast. We analyzed samples of stomach contents of individuals incidentally caught by artisanal fisheries. We investigated the geographical (Northern, Central, and Southern regions of São Paulo State coast, Brazil) and intrapopulation effects of season, sex, and age. We used the leave-one-out cross validation method to test for significance of the proportional similarity index, which measures the overlap between diet compositions. We found diet variation in the franciscana dolphin across different levels, from the geographical to the individual level, including the effects of season, sex, and age. Diet variation as a function of age suggests an ontogenetic diet shift for the species. Our findings indicate that ecological processes within local stocks must drive management actions at local geographic scales. Evidence for ecological differences between franciscana stocks is of great significance for the conservation of this threatened species.

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