An Evaluation of Sampling Strategies for Qualitative Surveys of Macro- Invertebrates in Rivers, Using Pond Nets

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Abstract
Qualitative samples with a pond net gave a better return than ''Surber'' or core samples in producing lists of taxa. Results obtained during faunal surveys of rivers are assessed to provide guidelines for the efficient design of sampling programs using pond nets. It is clear that the same method and oeprator should be used if comparison between samples is a requirement of the study. At least 6 samples are necessary to compile a representative list of taxa and more would be preferable if a comprehensive list is desired. Taxon yield is optimized by maximizing the number of sites, while increasing the number of sampling occasions reduces the likelihood of missing taxa which are strongly seasonal. Even replicated samples on the same day provide a considerable increase in yield. An adequate sampling program is considered to be 6 sampling occasions in alternate months through 1 yr, each with 4 replicate samples taken at 2 sites in each distinctive environmental zone along the river. Although only a narrow range of stream types was investigated, the sampling strategies should be suitable for different sites and different types of river. They should also have relevance to a wide range of trapping devices and situations where sequential samples are taken to produce lists of taxa in terrestrial as well as aquatic environments.