Ecological Niches and Trophic Levels of Fish Based on Feeding Habits in the Rekesan and Jumpinang Rivers Pasuruan Indonesia Relung Ekologi dan Tingkat Trofik Ikan Berdasarkan Kebiasaan Makan di Sungai Rekesan dan Sungai Jumpinang, Pasuruan, Indonesia

Abstract

River environmental changes influence aquatic organisms, particularly fish, by affecting food resource utilization and trophic interactions. This study analyzed feeding habits, trophic niche breadth, and trophic levels of fish in the Rekesan and Jumpinang Rivers, Pasuruan, Indonesia. A quantitative descriptive method with an ex post facto approach was applied using purposive sampling at upstream, midstream, and downstream stations in each river. Stomach contents were examined to determine diet composition. Trophic niche breadth was calculated using Levin’s index, and trophic levels were estimated based on dietary data. A total of 944 individuals representing eight species were recorded. Five species (Channa striata, Dermogenys pusila, Poecilia chica, Poecilia reticulata, and Rasbora argyrotaenia) were directly analyzed through stomach content examination, while trophic information for three species (Nemacheilus fasciatus, Puntius binotatus, and Pterygoplichthys pardalis) was obtained from relevant literature. Feeding habit values ranged from 0.57% to 97.43%, with phytoplankton and plant materials as dominant food sources. Niche breadth values ranged from 0.01 to 0.44, indicating narrow to moderate categories. Trophic levels ranged from 2.01 to 3.23, classifying the fish as herbivores and omnivores with plant or animal preferences. Differences in niche breadth and trophic position were observed between Poecilia chica and Poecilia reticulata across the two rivers, indicating trophic differentiation and variation in resource use along river sections.