Abstract
To understand the swimming ability of demersal fish for the design of a fishway, swimming experiments involving small Goby (Gymnogobius urotaenia sp.) during their upstream river migration period were conducted. The experiments were conducted using high velocity flows to prevent the Gobies from using the suction cups on their ventral fins. Our observations were as follows: 1) the body length of the Gobies was approximately 3-4 cm, and their average swimming speed was found to range from 70 cm·s-1 to 171 cm·s-1; 2) a swimming-curve formula defining the relationship between the swimming speed and swimming time was obtained; 3) at flow velocities of 83 cm·s-1 or less, 67% or more of the Gobies moved at least 50 cm; and 4) according to the swimming ability index, the swimming ability of Gobies exceeded that of the Ice Goby, Loach, and Medaka for the same body length.
