Habitat, diet, feeding and resting behaviour of the Korean endemic cobitid Iksookimia hugowolfeldi (Cobitidae, Pisces) in the wild

Abstract. A study on the habitat use and diet of Iksookimia hugowolfeldi, which is endemic to Korea, was carried out focusing on feeding and resting behaviour in the wild. This study focused on a valley stream in a forest on Geogeum Island (Eojeon-ri, Geumsanmyeon, Goheung-gun, Jeollanam-do, Korea) with a large population. The bottom substrate of this stream was mud (< 0.1 mm in diameter, 10 % relative abundance), sand (0.1–2 mm, 30 %), gravel (2–16 mm, 20 %), pebbles (16–64 mm, 20 %), cobbles (64–256 mm, 10 %), and boulders (> 256 mm, 10 %), with an Aa-Bb river type and a slow current (0.1 m/s). The food sources analyzed based on the index of relative importance (IRI) included Diptera (70.98 %), Phryganeidae (10.46 %), Branchiopoda (9.74 %), Harpacticidae (8.33 %), Ephemeroptera (0.47 %) and other (0.02 %). As a diurnal and benthic filter feeder, two main feeding behaviours were observed: feeding on surface (sand, cobble) and on sand-cobble digging. Resting behaviour predominantly occurred on the surface of sand and cobbles, and sometimes while buried in the sand. Daily feeding behaviour was more active at the highest water temperature of 22.1– 23.7 °C from 14:00 to 15:00, and feeding behaviour occurred more frequently in July to August, at temperatures as high as 22–24 °C. Meanwhile, while the water temperature is below 8 °C, they are getting around in the water by being hid in or buried in the substrate. In that season, the empty stomach rate was higher than in other seasons.