We are not convinced that these claims are true or even at issue. Because a Surber sampler samples only part of a riffle, a single sample may not be precise enough to judge stream condition. Using a bootstrap resampling algorithm, Fore and Karr simulated the effects of taking one, three, or five replicates at a site. With only one replicate, a metric could either increase or decrease depending on which of the five replicates was chosen by the bootstrap algorithm. In practice, therefore, the numerical value of a metric calculated using a single Surber sample at a site would depend on where in the riffle that sample had been taken.
Metric precision increases little if five replicates are collected instead of three.
Thus we conclude that the increased costs of sample collection and analysis for three replicates over one are justified, but not those for five replicates. Note, however, that precision increases relatively little from three to five replicates. The lower two graphs clearly show that the relative abundance of predators increases as resource condition improves. These methods work well in small to midsized streams. It is especially important to collect and count a sufficient number of insects to characterize the biota in multiple dimensions.