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Evaluating adequacy of the representative stream reach used in invertebrate monitoring programs

C.F. Rabeni·N. Wang·R.J. Sarver
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Abstract

Selection of a representative stream reach is implicitly or explicitly recommended in many biomonitoring protocols using benthic invertebrates. We evaluated the adequacy of sampling a single stream reach selected on the basis of its appearance. We 1st demonstrated the precision of our within-reach sampling. Then we sampled 3 or 4 reaches (each ∼20× mean width) within an 8-16 km segment on each of 8 streams in 3 ecoregions and calculated 4 common metrics: 1) total taxa; 2) Ephemeroptera, Plecoptera, and Trichoptera taxa; 3) biotic index; and 4) Shannon's diversity index. In only 6% of possible cases was the coefficient of variation for any of the metrics reduced >10% by sampling additional reaches. Sampling a 2nd reach on a stream improved the ability to detect impairment by an average of only 9.3%. Sampling a 3rd reach on a stream additionally improved ability to detect impairment by only 4.5%. We concluded that a single well-chosen reach, if adequately sampled, can be representative of an entire stream segment, and sampling additional reaches within a segment may not be cost effective.

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C.F. Rabeni, N. Wang, R.J. Sarver. 1999. Evaluating adequacy of the representative stream reach used in invertebrate monitoring programs. https://doi.org/10.2307/1468466

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