scope:

The colonization samplers described allow water quality to be assessed by providing a collection of macro-invertebrates indicative of the water quality at the sites of concern. They do not sample the natural invertebrate fauna, which may be restricted by physical conditions unrelated to water quality, and are to be used when studying lowland river waters of depth over 1 m. The deep water samplers described are for use in rivers deeper than 1 m on substrata ranging from mud to stones. They are unsuitable when sampling over macrophytes or stones of sizes greater than about 15 cm, or in very fast flowing water.