Lamprey abundance (IAL — 2013) — Sélune Observatory

The upstream course of the Sélune is not accessible to migratory fish due to the two hydroelectric dams. The lampreys are blocked about fifteen kilometres from the sea by the first inpassable dam of La Roche which drinks. The method used to sample lampreys is the method developed by Lasne et al. (2010) to collect very small individuals more effectively than by electric fishing. The method is based on the use of a tool derived from the Surber net, allowing the ammococet to be sampled in a standardised manner. This enclosure makes it possible to carry out spot sampling, in the same way as EPAs. The realisation of a sampling point takes place in several stages. After locating a favourable microhabitat, a box is buried in the substrate to a depth of about 15 cm. The operator then removes the substrate and deposits it into the net. The water column in the box is filtered and the sediments in the net deposited on a sieve to recover all the ammocets. These are measured and genetic samples are taken when their size permits. A total of 30 samples are taken per station.