| Abstract: | Heat resistance times of 10 species of crustaceans representing 5 families and 65 fishes from 32 families were determined during June 1974 through September 1975 to estimate percentage survival in the discharge canal system of the P. H. Robinson Generating Station, Bacliff, Texas. Animals were taken directly from the intake canal and placed at experimental temperatures. Individual resistance times increased with an increase in intake canal temperature and with a decrease in test temperature. Most aquatic animals captured at similar temperatures were less resistant to heat death in April to mid-June than in late August and September. Few species showed a relationship between individual resistance time and total length. Summer discharge canal temperatures above and below the cooling towers were around 40 and under 35 C, respectively. Three-h LD50 temperatures of most organisms except Anchoa mitchilli and Trichiurus lepturus were equal to or greater than 35 C and 0.5-h LD100 temperatures of most species were lower than 40 C during the summer (June - September). A stochastic application, based on organisms exposed to elevated temperatures 30 min afferent and 150 min efferent to the cooling towers, indicated that summer mortality rates per minute of all species tested except four fishes (A. mitchilli, A. hepsetus, Dorosoma petenense and T. lepturus) were 0 at an efferent temperature of 35 C. Death rates at an afferent temperature of 40 C for Palaemonetes pugio, Penaeus setiferus, P. aztecus, Callinectes sapidus, Elops saurus, Arius fells, Opsanus beta, salt-marsh fishes (Cyprinodontidae and Poeciliidae). Eucinostomus sp., Mugil cephalus and M. curema ranged from 0.2 to 7.6% per minute and were greater than 11% per minute for 40 other organisms.. |
|---|