Heat Death of Fish in Shrinking Stream Pools

Responses of 14 species of fish were observed in two shallow (<20 cm), isolated pools of Indian Creek, Butler County, Ohio, when maximum water temperatures reached 38.3-39.5 C. Individuals of 12 species died from thermal stress in one pool. Despite occurrence of these high water temperatures on at least two separate dates, individuals of four (of 12) and 14 (of 14) species of fish survived in the two pools, respectively. Mean critical thermal maxima (CTM) of six species of fish (striped shiner Notropis chrysocephalus; silverjaw minnow Ericymba buccata; bluntnose minnow Pimephales notatus; central stoneroller Campostoma anomalum; quillback carpsucker Carpiodes cyprinus; fantail darter Etheostoma flabellare) collected from one of the pools after exposure to the high temperatures ranged from 36.2-38.8 C. Survival of fish in the pools was attributed to their elevated thermal tolerances (CTMs), and the use of shaded cooler refugia in each pool.