ESR prepress abstract   -  DOI: https://doi.org/10.3354/esr01364

ABSTRACT: The bitterling, Acheilognathus majusculus, is a freshwater fish, endemic to the Nakdong and Seomjin rivers in South Korea, and listed as an endangered species by Ministry of Environment in South Korea due to its biological, ecological, and genetic importance. The dietary information of A. majusculus is crucial for understanding its role within an ecosystem and planning its restoration strategy. In this study, we employed a non-invasive DNA metabarcoding approach to characterize the diet using 34 A. majusculus fecal samples collected from the Nakdong and Seomjin rivers. Analysis of 1642037 clean reads generated by applying the next generation sequencing yielded 210 amplicon sequence variants (ASVs). Taxonomic assignment successfully identified 10 phyla, 16 classes, 23 orders, 29 families, 29 genera, and 26 species. Green algae (Chlorophyta) and diatoms (Bacillariophyta) were predominantly detected in all samples, with percentages ranging from 5.56 to 43.59% and 30.00 to 66.67%, respectively. Smaller percentages of other taxa such as parasitic protists of Ichthyosporea (Opisthokonta incertae sedis), ciliates (Ciliophora), mostly eustigmatophytes (Ochrophyta), fungi (Ascomycota), vertebrates (Chordata), flatworms (Platyhelminthes), and green plants (Streptophyta) were also detected. The dietary composition of A. majusculus remained consistent irrespective of body size or sex. However, it exhibited pronounced seasonal variation in the summer samples compared to the others, i.e., spring and fall, as demonstrated by beta-diversity analyses. These findings provide valuable insights into the dietary composition and seasonal variations of A. majusculus and highlight the need to protect and restore aquatic habitats and regulate water flow from weirs to ensure the consistent availability of essential food resources for effective habitat management strategies of this endangered species.