The assessment of the flow requirements for upstream migration of salmonids in some rivers of North West England

This is the assessment of the flow requirements for upstream migration of salmonids in some rivers of North West England produced by the North West Water Authority in 1985. This report focuses on the automatic fish counters operating on the resistivity principle used for several years in North West England. This report aims to investigate the flow requirements for upstream migration of salmon and migratory trout. The data obtained confirmed that during summer months most fish movement occurs in the higher range of the available flows, but the migration flow range varied from year to year, depending on prevailing river levels. Of the other environmental variables measured, only water temperature and incident light intensity appear to have any direct association with fish movement. Information on migration flow ranges were used in conjunction with computer simulations of the effects of abstraction proposals on historical flows to assess the implications of these proposals for migratory fish.