Height and horizontal distance of territorial attacks by ayu (Plecoglossus altivelis altivelis) were observed in aquaria

Abstract

The height and horizontal distance of territorial attacks by ayu (Plecoglossus altivelis altivelis) were observed in aquaria. Territory holders responded towards intruders when approached to within 30–40 cm, chasing them for 40–100 cm. Such chases ceased ca. 30–40 cm from the bottom (in 50–100 cm water depth), indicating that territorial defense limits in water depths greater than 50 cm were about 30–40 cm (vertical distance) and 40–100 cm (horizontal distance).