Aquatic Macroinvertebrates

Abstract

Sampling of aquatic macroinvertebrates requires techniques that are efficient and representative. Stratification of sampling units is a practical way of ensuring representative coverage of the habitat. However, efficiency of sampling devices used in the field and techniques for extraction of specimens from samples has rarely been assessed. Commonly used qualitative and quantitative samplers are described as well as the situations in which a particular device is most likely to be useful. The efficiency of these devices can be estimated using a technique known as removal sampling, whose underlying statistical theory is well understood. The laboratory examination of samples is straightforward but tedious. Flotation of specimens from inorganic material and subsampling are two methods of speeding up laboratory processing. Small cryptic species or small instars are easily obscured by detritus when picking specimens from samples under low magnification. By scanning samples twice the efficiency of extraction of specimens can be estimated.