Upstream migration activity of cyprinids and percids in a channel, monitored by a horizontal split-beam echosounderJuha Lilja, Tapio Keskinen, Timo J. Marjomäki, Pentti Valkeajärvi and Juha KarjalainenAquat. Living Resour., 16 3 (2003) 185-190DOI: https://doi.org/10.1016/S0990-7440(03)00016-0