The Danube-Net-Basket-Sampler - A simple but effective device for sampling benthic invertebrates in deep and large stony rivers
Ofenböck, G.; Moog, O.
Quantitative sampling in large, deep rivers is both difficult and cost-intensive. Areas such as steep banks, deep runs and in high current velocity are often inaccessable and standard methods are difficult to apply. Dredging nets, grabs, corers and air-lift samplers can be used, but they have been developed for research and are usually too expensive for routine monitoring programs. Colonization samplers containing artificial substrate can provide a valid alternative, but nevertheless are mostly too complicated for routine use. To overcome these problems a new colonization sampler based on the "Belgian artificial substrate sampler" (de Pauw 1993) was developed and tested for its efficiency and used for the study. At two sites in the Danube near Vienna samples from the colonizing device were compared with samples taken from natural substrates with a Surber-sampler. The sampling method decribed proved to produce reproducible results and is practicable for routine monitoring. The collecting gear consists of inexpensive and readily available materials, sampling can be carried out quickly with few personnel, and handling is easy. Although the Danube-Net-Basket-Sampler seems to display some degree of selectivity, it provides a representative sample of macroinvertebrate fauna with respect to taxonomic composition, individual numbers, and biomass, sufficient for a correct assessment of a given set of metrics used for routine water quality assessment. The colonization samples also support the analysis of functional ecosystem aspects, such as the distribution of functional-feeding guilds and zonation aspects.