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ESR prepress abstract   -  DOI: https://doi.org/10.3354/esr01113

Shedding light on the river and sea lamprey within western European marine waters

Sophie A. M. Elliott*, Noémie Deleys, Etienne Rivot, Anthony Acou, Elodie Réveillac, Laurent Beaulaton

*Corresponding author:

ABSTRACT: Lampreys are ancestral jawless vertebrates with particularly complex life histories. Due to increased anthropogenic pressures, population declines have been observed. For semelparous diadromous lampreys, the marine phase remains largely a black box, making targeted management and conservation measures difficult to implement. Here, we collated a database of 168 904 hauls from both fisheries-dependent and independent surveys between 1965 and 2019. Lampreys were observed in only 2524 hauls (<1% lamprey presence). 421 sea lamprey Petromyzon marinus and 300 European river lamprey Lampetra fluviatilis were identified. Sizes ranged from 13 cm to 92 cm and 14 cm to 42 cm respectively. The majority of lampreys (61%) were caught by mobile demersal gear types. A higher presence of both species was recorded within the Greater North Sea, followed by the Bay of Biscay. L. fluviatilis was observed closer to the coast than P. marinus. For both lampreys, there was an increase in size with distance from the coast. P. marinus were predominantly <60 cm and observed from August to February, indicating they were sexually immature juveniles migrating out to sea. For L. fluviatilis, the majority were thought to be adults (>20 cm) and occurred in autumn, indicating inshore migration. Our observations provide insight into the ecology of lampreys at sea, and highlight study locations and gear types, which may be more pertinent for future research. Greater awareness is needed during surveys to collate catch information on lamprey and improve understanding of their ecology and phenology at sea.