Sampling sufficiency in stomach content surveys of omnivorous fish species

ABSTRACT Feeding research in fish has offered understanding into the ecology of individuals, populations, and ecosystems. In these studies, analyzing enough stomachs is crucial to determine a species’ diet. This research evaluates the number of stomachs needed to characterize the diet of omnivorous fish species by employing cumulative prey curves, non-parametric estimators, and rarefaction/extrapolation curves. The Feeding Index was calculated by utilizing a wide taxonomic classification of food items to determine the number of individuals needed to characterize trophic groups. The stomach contents of three species: Megaleporinus garmani (n = 174), Trachelyopterus galeatus (n = 99), and Wertheimeria maculata (n = 68) was analyzed. The cumulative prey curves fail to reach an asymptote for any species. In comparison to richness estimators, the observed diversity of prey varied between 73 and 91% across different species. The extrapolation curves approach an asymptote in the case of T. galeatus and W. maculata, reinforcing the declining counts of food item singletons and doubletons noted in their dietary accumulation curves. According to the Feeding Index, analyzing 30 to 60 stomachs is adequate to determine the primary dietary components. A reduced number of stomachs (25 to 35) is needed to identify feeding guilds. Due to the wider diets of omnivorous species, a larger sample is required to properly characterize their diet. Elements like research goals, required detail level, seasonal variations, and species-specific characteristics should be taken into account when determining the number of stomachs to analyze, to guarantee strong and dependable outcomes.