Abstract
Dietary analysis has contributed to our understanding of animal niches, interspecific interactions, community structure and the flow of matter and energy in food webs. We employed three methods of dietary analysis to estimate trophic niche overlap between two peacock bass species, Cichla cataractae and Cichla ocellaris , across sympatric (Essequibo River) and allopatric (Rupununi and Rewa Rivers) populations in Guyana – visual gut contents analysis, gut contents metabarcoding and stable isotope (δ 13 C, δ 15 N) analysis. During the dry season, both piscivorous species exhibited generalist feeding strategies and little evidence of trophic niche segregation with respect to prey taxonomic diversity. Metabarcoding identified 92 prey taxa spanning 28 genera, with Characiformes, Siluriformes and Cichliformes dominant in diets of all populations. Visual gut contents analyses corresponded with metabarcoding results but revealed C. cataractae consumed significantly larger prey than C. ocellaris , consistent with the larger mouth gape of C. cataractae . Stable isotope analysis indicated C. cataractae had higher nitrogen ratios than C. ocellaris , and the two species overlapped broadly with respect to carbon ratios. Overall, there was broad isotopic overlap between species and between allopatric and sympatric populations of C. ocellaris (≥ 70%). These findings suggest food resource partitioning with respect to taxonomic diversity is relatively unimportant for coexistence of these cryptic species, and prey size and habitat selection are the principal mechanisms of niche partitioning during the annual low‐water season.