STOCHASTIC APPROACH TO PREDICT 

 SURVIVAL OF ESTUARINE ANIMALS EXPOSED 

 TO HOT DISCHARGE EFFLUENT 



K. S. CHUNG* and KIRK STRAWN 



Department of Wildlife and Fisheries Sciences, Texas A. & M. University, 



College Station, Texas 



ABSTRACT 



The stochastic model was used to predict survival probabilities for aquatic 

 animals in intake water exposed to hot discharge effluent for 180 min (30 min 

 afferent and 150 min efferent to the cooling towers) on the basis of 

 water-passage times. The least-squares method was used to estimate seasonal 

 mortality rates of 8 species of crustaceans and 46 fishes at several test 

 temperatures for each of three seasons. During the hot season (June- 

 September), mortality rates (fraction/min) were 23% or greater for most 

 organisms at 40 C (discharge-canal temperature afferent to the cooling towers) 

 and zero for most animals at 35 C (discharge temperature efferent to the 

 towers). Survival probabilities for macrocrustaceans and fishes after a 180-min 

 passage through the discharge-canal system, in terms of average seasonal 

 temperature, ranged from to 96% from June— September and from to 61% 

 for the 56 species tested. Almost all mortality occurred during the 30-min 

 passage before the cooling towers. From October to May, predicted survival for 

 all animals except the bay anchovy was 100% after a 180-min passage through 

 the discharge-canal system (survival for the anchovy was 88% in the cool season, 

 May and October). 



Much research has been focused on industrial use of water for 

 coohng purposes and the effects on aquatic organisms of heated 

 discharge effluent (Naylor, 1965; Adams, 1969; Churchill and 

 Wojtalik, 1969; Vernberg and Vernberg, 1969; Cairns, 1972; Gibbons 

 and Sharitz, 1974; Esch and McFarlane, 1976). Few studies provide 



*Present address: Instituto Oceanografico, Universidad de Oriente, Cumana, 

 Venezuela. 



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