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

Le résumé fourni par la source

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

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