37. Cullen analyzed variations in silver eel catch on the River Shannon at Killaloe in Ireland. Lights inhibited catches; daytime catches were negligible and yellow eels were only very rarely seen. Water flow had important influence on catches. Wickström commented on the occasional females of exceptional size and suggested that their growth and silvering strategies may differ from the normal.
38. Knights reviewed information on design and validation of the efficacy of passes for juvenile eels. He stressed the need for careful design, incorporating suitable flow rates and for the use of rubble or other appropriate substrate at entrance and exit.
39. White presented results of a 3 year study of migration (using traps on migration barriers) in the Severn and Avon rivers in England. Elver catches at the tidal head were <0.1% of the commercial glass eel catch, but natural mortality was thought to be a major factor. Numbers of migrants trapped decreased, but size and age increased with the number of migration barriers. Migratory tendencies of individuals were very variable and maximum migrations correlated with temperatures > 16°C. The use of eel passes and stocking was endorsed.
