抄録
Biwa salmon, endemic to Lake Biwa, central Japan, is an important species for local fisheries. Because little is known about the species spawning sites, despite the importance of such for effective management, suitable spawning sites for Biwa salmon in the Ishida River entering Lake Biwa were evaluated, focusing on distribution, water depth, current velocity and gravel composition (substrate). Many spawning redds were concentrated immediately downstream of an almost impassable weir (Umehara weir, approximately 5.2 km upstream from the river mouth). Statistical analyses of other factors, using Manly’s selection index, revealed that adult females have significant preferences when selecting spawning redds: water depth of 10‒30 cm, current velocity of 20‒30 cm/s and 40-50 cm/s, and a specific substrate (pebbles of 17‒64 mm).
