Great Basin Naturalist


The life history of the endangered Kendall Warm Springs dace (Rhinichthys osculus thermalis) is largely unknown. Our study of its reproduction, sources of mortality, and diet indicated that Kendall Warm Springs dace seem to be reproductively active throughout the year, but the rate of reproduction appears to decrease during the winter. Males become sexually mature at 34 mm total length and females at 40 mm total length. We observed 2 sources of mortality: (1) emigration from the warm spring over a waterfall into the Green River and (2) predation on larvae by dragonfly (Libellula saturata) nymphs. Stomachs of Kendall Warm Springs dace contained small (≤1.5 mm total length) benthic invertebrates, primarily dipterans and mollusks.