From shallow to deep waters: habitats used by larval lampreys (genus Petromyzon and Lampetra) over a western European basin

–  Habitat requirements of lamprey ammocoetes (Petromyzon marinus and Lampetra genus) were investigated, for the first time, from shallow to deep waters, at different spatial scales across the Gironde-Dordogne continuum, thanks to a water suction dredge. Fish-habitat relationships were assessed through two complementary statistical analyses: habitat-use curves and habitat suitability models using the Boosted Regression Trees (BRT) technique. Analyses were performed on a small-size data set that was characterised by the low prevalence of lamprey. The sea lamprey larvae occurred in deeper areas than their Lampetra genus counterparts. ‘Pools’ of 2 m’ depth and more were optimal habitats for the former species. Among the environmental variables retained to model lamprey occurrences, the mesohabitat (a categorical variable) was demonstrated to be highly influential, in terms of fine grain-size substratum and vegetation cover. These preliminary results suggest that monitoring using the water suction dredge method may contribute to sea lamprey conservation.