Feeding ecology of Orestias agassii (Cyprinodontidae: Cyprinodontiformes) in the high Andean environments of Peru

Orestias agassii is the most widely distributed, abundant, and variable species within the Orestias complex. However, knowledge about its ecological aspects remains limited. Therefore, this study aimed to determine the feeding preferences of O. agassii in high Andean aquatic environments of the Mantaro and Apurímac river basins. Sampling was conducted in seven habitats (one river, one stream, three peatlands, and two lakes) in April (T1) and September (T2) of 2010 using standardized methodology. A total of 343 stomach contents were analyzed, and frequency of occurrence, volumetric index, alimentary index (IA), and trophic niche breadth (Levin’s index) were calculated. Food items were summarized through a Principal Coordinates Analysis (PCoA). Twenty-three food items were recorded, mainly aquatic insect larvae (eleven families). The most frequent items were Chironomidae insects, and the largest volume corresponded to Chironomidae in T1 and algae in T2. The % IA was higher for aquatic insects in peatlands and rivers in T1, whereas algae were more important in lakes. In T2, % IA was higher for aquatic insects across all habitats. ANOVA on the first PCoA axis showed significant differences between seasons and habitats. Levin’s index indicated dietary specialization. The results demonstrate spatial and temporal variability in diet as a consequence of the diversity and richness of the environments, which present unique characteristics. This knowledge will provide valuable information for the proper management and conservation of these ecosystems.