The feeding habits of juvenile Chaenogobius annularis were examined based on gut content analysis of 281 individuals, collected from May to June 2011 in the coastal water of Geoje, Korea. Copepods were the main source of food for C. annularis, which constituted 61.6% in IRI. Barnacle larvae was the second largest dietary component. Graphical analysis of the diet composition showed that C. annularis was a specialized predator characterized by strong individual feeding specialization. Both small and large size class of C. annularis mainly consumed harpacticoida and cirripedia cypris.

To investigate the trophic relationship between the fresh water fishes and aquatic invertebrates, the research of their prey is important. However, the morphological identification of the prey in the fish intestine is very difficult due to the process of digestion. Thus, we conducted the DNA barcoding methods for aquatic insect samples from the gut of fresh water fishes for identifying hardly recognizable species. All benthic macroinvetebrates and manchurian trouts were collected from the upper streams of Inje-gun, Korea, in spring and summer, 2013. A total of 27 unique taxa were recognized, among which 23 species were identified by morphology, and 4 unrecognizable individuals were identified based on mitochondrial cytochrome C oxidase I (Mt-COI). As the results of this study, Ephemerella sp., Neophylax sp., Neophylax sp., and Pteronarcys sp. are verified to the genus level by DNA barcoding.