Variation between Technicians Sorting Benthic Macroinvertebrate Samples

After identification and enumeration, specimens sorted from 18 benthic macroinvertebrate samples by two technicians were returned to corresponding sample residue. Unknown to technicians, the samples were remixed and relabeled with new collection dates and then sorted as if newly collected. By chance, 13 samples were sorted by both technicians. A two-tailed t-test (p≤0.05) indicated significant difference in number of sorted specimens, but no difference in sorting time and in number of sorted genera.