In currently procedures, Japanese eel Anguilla japonica larvae are fed at the bottom of rearing tanks. Therefore, the swimming ability of larvae should be considered for designing procedures for rearing them. This study analyzed the swimming ability and the amount of intestine fullness of Japanese eel larvae in 1 kl-scale tanks. Our results indicate that larvae can swim downward with faster than 6 mm/s at 7 days after hatching (DAH). Moreover, food in the intestines of larvae saturated at around 7 DAH. Consequently, a swimming speed of about 6 mm/s might be necessary to feed them efficiently in a 1 kl-scale tank.
