Upstream spawning migration of river lamprey (Lampetra fluviatilis) in the River Yorkshire Ouse, 2018-2020

This study investigated the upstream spawning migration of anadromous river lamprey in the Yorkshire Ouse, a highly dendritic and heavily fragmented tributary of the Humber Estuary (home to one of the largest UK river lamprey populations). The main English lamprey fishery operates within the tidal reaches of the Yorkshire Ouse. The study occurred over two consecutive (2018/19 & 2019/20) and highly contrasting (dry & wet) flow years. River lamprey were either single (PIT only) tagged or double (acoustic and PIT) tagged and released at three different locations. Single tagged lamprey were released at Cawood, downstream of the commercial fishery and Naburn Weir. Double tagged lamprey were evenly split between Cawood, upstream of the first (Naburn Weir) and second (Linton Weir) main river barriers. Overall, the study examined commercial fishery exploitation as well as the catchment-wide migration and the impact if the two large main river barriers on onward migration.