Cao, Y., D.P. Larsen, and R.M. Hughes. 2001. Evaluating sampling sufficiency in fish assemblage surveys -- a similarity-based approach. Can. J. Fish. Aquat. Sci. 58:1782-1793.
How many and what fish species occur at a site at one particular time provide basic information for assessing biological integrity, inferring fish assemblage-environment relationships and examining biodiversity patterns. The conclusions are often dependent on whether and how sufficiently species richness and composition of fish assemblages are characterized by fish sampling. The percentage of total species richness (%TSRtru) obtained in a sample is an explicit measure of sampling sufficiency. However, because species curves often do not level off and TSRtru is unknown, the sampling sufficiency cannot be determined directly. To overcome this difficulty, we developed a new approach, which is based on the relationship between %TSRtru and the similarity among replicate samples (replicate-similarity). With replicate-similarity measured with Jaccard Coefficient (JC), a simple relationship was established: %TSRtru = 100 JC. Five river and stream sites where TSRtru was reached or approached during sampling were selected from three datasets to evaluate this relationship. We used the approach to estimate the sample sizes required for 90%, 95% and 100%TSRtru for each site in the datasets. The results strongly support using the new approach in determining sampling sufficiency in fish assemblage surveys.