Passage efficiency and behaviour of sea lampreys ( <i>Petromyzon marinus</i> , Linnaeus 1758) at a large marine–freshwater barrier

Passage success of sea lampreys Petromyzon marinus and behaviour in the vicinity man-made structures such as marine–freshwater barriers are poorly understood. To mitigate these migratory problems, a better understanding passage is needed. investigate this, 25 were tagged with V7 VEMCO acoustic transmitters at large marine-freshwater barrier, consisting ten sluice gates ship lock complex Netherlands. Overall was assessed to be 16%, four passing gates, while none passed locks. Successful through barrier occurred either beginning or end discharge period, when water level differences between lake thus velocities relatively low. Most lamprey showed exploratory searching but only for short duration, before leaving area again unsuccessful. Low search duration likely related unnatural infrequent occurrence flow lasting windows suitable conditions gates. poor migration current adapted management, fish facility lower longer continuous opportunities