PATTEN S1IORT-TKRM THERMAL RESISTANCE OF CRAB ZOEAE 



ranged from 28° to 32°C, except that H. orego- 

 nensis had a TL 50 of 34°C for the 1-h test. 



The maximum temperature increase in a steam 

 electric station that will not cause mortality to the 

 species studied can be estimated from the sea- 

 water temperature in Puget Sound and the 

 maximum temperatures tolerated by zoeae. Sur- 

 face temperatures of Puget Sound range from 

 about 10°C in the spring when most zoeae hatch to 

 15°C or more in some locations in the summer 

 (Wennekens 1959). Temperatures in heat ex- 

 changers can be increased 14°C in the spring and 

 9°C in the summer without causing direct or 

 indirect mortalities to the least resistant species. 

 Synergistic effects from the release of toxic 

 chemicals and from mechanical damage may act 

 to lower the thermal maximums tolerated. 



Knowledge of the temperature tolerance of the 

 zoeae studied provides a partial input into the 

 assessment of the impact of a steam electric 

 station using Puget Sound waters for cooling. 

 Zoeae are generally a minor component of 

 zooplankton within the depths of Puget Sound 

 that would be subject to entrainment (Hebard 

 1956; Patten unpubl. data). Also, the volume of 

 water entrained by a steam electric station would 

 be small in comparison to that of Puget Sound. 

 Therefore, if all entrained zoeae were destroyed in 

 a steam electric station, the proportion lost may be 

 of minor concern on the population level. Losses of 

 zoeae from high temperature conditions may be 

 more serious if a series of steam electric stations 

 used Puget Sound waters for cooling. In this case, 

 some conservation measures should be con- 

 sidered. 



ACKNOWLEDGMENTS 



I thank Eugene Collias of the University of 

 Washington Department of Oceanography for 

 providing me with water quality data from Elliot 

 Point, Wash. I also thank Warren Ames, Donovan 

 Craddock, and George Slusser of the National 

 Marine Fisheries Service for assisting me. 



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