How accurately can retention of benthic macrofauna by a particular mesh size be predicted from body size of organisms?

Abstract

Size of organisms is frequently the prime criterion in selecting a mesh size to sample benthic assemblages. This study quantified the accuracy in estimating the sampling efficiency of screens from body size of macrozoobenthos in the upper, sandy, reaches of a small, shallow estuary, where the community consisted primarily of peracarid crustaceans and polychaetes. Body size of organisms retained by a 0.25, 0.5 and 1.0 mm screen was used to predict the retention efficiency of each gear by multiple discriminant analysis (MDA), or by simply assuming that an animal of known size will be retained by a screen of the same aperture size (‘body aperture match’). MDA-models classified about 70% of all cases correctly, whereas matching of body-to screen-size gave at best spurious, and often seriously wrong estimates of retention efficiency for all tested mesh sizes. Regardless of the method employed, body size was found to be an extremely poor predictor of mesh retention. Consequently, sampling performance of each mesh size in a particular habitat × community combination should be determined experimentally and not from body size measurements obtained during pilot studies.