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

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.

猎物可获得性的差异可导致地理结构种群产生食性分化。在同一分布区域内，食性差异也可能受季节、性别、年龄以及个体间差异的影响。然而，在食性相关研究中，这些影响因素很少被同时纳入考量。当前学界正大力开展海洋生物种群与生态特征研究，以期制定科学的保护与管理准则。在为受威胁物种制定保护准则时，食性差异分析是核心关切之一，对于猎物可获得性可能因商业捕捞而下降的海洋捕食者而言尤为如此。我们以巴西圣保罗州沿岸的拉河豚（franciscana dolphin, *Pontoporia blainvillei*）为研究对象，通过分析其地理与种群内部层级的食性差异来识别渔业种群单元。我们采集并分析了小型传统捕捞渔业兼捕的拉河豚个体的胃容物样本，考察了巴西圣保罗州沿岸北部、中部与南部三个地理区域内，季节、性别与年龄对食性的种群内与地理层面影响。我们采用留一交叉验证法（leave-one-out cross validation）对用于衡量食性组成重叠度的比例相似性指数（proportional similarity index）的显著性进行了检验。研究结果显示，拉河豚的食性差异存在多个层级：从地理种群到个体层面，均受季节、性别与年龄因素的影响。食性随年龄产生的差异表明该物种存在个体发育食性转换现象。本研究结果表明，地方种群内部的生态过程应作为制定地方尺度管理措施的依据。拉河豚不同种群间存在生态差异的相关证据，对该受威胁物种的保护工作具有重要意义。