DESCRIPTION AND EVALUATION OF A SAMPLING STRATEGY FOR MACROINVERTEBRATE COMMUNITIES IN BASQUE RIVERS (SPAIN)

This paper describes the results of a pilot study on the macroinvertebrate communities occurring in a fast-flowing river in Northern Spain. The objective was to devise a sampling strategy for use on a series of Basque rivers included in a site classification study. Two contrasted sites were chosen for the pilot-study on the River Lea (Bizkaia), at the headwaters and near the mouth. Taxon richness and distribution across the river was examined using two sampling techniques at each site. It was concluded that, ideally, timed sampling units should be collected at intervals across a river transect in order to acquire a representative list of taxa. In addition, adequate sampling in marginal areas was stressed because a number of taxa appeared to be exclusive to marginal areas. Sampling location and total sampling effort were also shown to be a major consideration when taxon lists were acquired for the application of routine biological surveillance techniques.