A new sampling technique for larval lamprey population assessment in small river catchments

Larval lampreys were sampled in a small river using a new method modified from the Surber bottom sampler for invertebrates. This method uses a rectangular dredge to sample a constant and small surface of sediments in soft substrate areas. It was compared to a classical point abundance sampling by electrofishing. Both methods generated large numbers of small samples encompassing the spatial heterogeneity of ammocoete distributions. However, the bottom sampler provided samples with higher abundance and was more efficient for small individuals. Furthermore, the equipment is cheap and the method is cost-effective, since it can be operated by only two people. It could therefore be applied at a large scale to collect information on lamprey populations and contribute to knowledge of their distribution, abundance and, in fine, to devise better conservation measures.