Sampling fauna in aquifers: a comparison of net-sampling and pumping

Two devices frequently used for sampling groundwater fauna in aquifers were compared: the phreatobiological net-sampler and the centrifugal pump. Thes e two methods were tested in a French Pyrenean alluvial aquifer during two contrasting seasons. Macrocrustacean (amphipods. isopods) and microcrustace an taxa (cyclopoids) were collected from 15 wells with different characteri stics (piezometric level, depth, water extraction, hydrogeological settings ) in order to compare the relative abundance patterns obtained with the two methods. Very similar patterns were observed using either the phreatobiolo gical net or the pump, whatever the taxa considered. Species characteristic s (size, ecological preferences, locomotory behaviour) did not influence th e results. The global efficiency of the methods appeared to depend on sampl e size, i.e. on the abundance of the species collected. The advantages and disadvantages of the two methods are discussed relative to the sampling cri teria (field framework, damage to fauna, ease of use, convenience). Under s ome conditions, the phreatobiological net-sampler can be considered a valua ble alternative to pumping in aquifers.