Cyprinid fishes as samplers of benthic diatom communities in freshwater streams of varying water quality

The diatom composition of natural substrates in streams of different water qualities was compared among samples collected by researchers and samples collected from the intestine contents of three species of Cyprinid fishes: Campostonia anomalum, Pimephales notatus, and Semotilus atromaculatus. Campostoma and Pimephales were found to be robust samplers that efficiently collected diverse, representative diatom samples. Semotilus were adequate diatom samplers but collected the most diverse samples. In no instance were water-quality indices calculated from Pimephales samples significantly different from human-collected composite samples, whereas Campostoma and Semotilus samples diverged slightly from human-collected composite samples. Internal similarities of fish-collected samples were not significantly higher than those of human-collected samples, indicating that the fish were indiscriminately foraging on diatoms. Furthermore, samples clustered primarily by stream, indicating that fish-collected samples of diatoms were as representative of the stream as those collected by human researchers. By all standards measured in this study, these three fish species sample the benthic diatom community of mid-order streams with a facility equal to that of trained ecologists.