Behavior and Forward Movement Ability of Underyearling Cottus reinii in Running Water

Abstract

Swimming experiments were conducted on wild 0+ Cottus reinii with an average standard body length of 2.5 cm. Our key findings are: 1) C. reinii exhibited repetitive behaviors of resting on the bottom and forward movement in running water. During forward locomotion, propulsion was achieved by laterally oscillating the body, using the caudal fin for thrust. While at rest on the substrate, they maintained their position by pressing their pectoral fins against it. 2) The flow velocity during measurement ranges from 20-60 cm/s, 95% of one swimming time from resting to resting were <1 s. The maximum swimming speed measured during this period was 100 cm/s. 3) The flow velocity enabling forward movement for C. reinii was estimated to be <70 cm/s. 4) Flow velocities of 50 cm/s resulted in 55% of C. reinii exhibiting forward movement ≥30 cm in running water. However, this percentage decreased to 17% under flow velocity conditions of 60 cm/s.