798 POJE, GINN, AND O'CONNOR 



maximum flows through the simulator, a AT of to 25°C can be 

 achieved rapidly on one or both loops and maintained at tolerances 

 of ±0.25°C. Temperature is monitored before the y junction and at 

 the end of each condenser tube. 



Pressure 



As the speed of the circulating pump increases, the pressure of 

 water flowing through the simulator increases. In addition, the 

 weight of the column of water draining the condenser tube exerts a 

 subatmospheric pressure on the system. Varying the length of these 

 sections (G) alters the magnitude of the suction pressure. The 

 elevation of the condenser tubes can be adjusted to three heights 

 above the base skid, 3.05, 4.39 and 5.49 m. By varying flow and 

 height of the condenser loops, we can regulate pressures at the 

 condenser inlet over the range from 0.5 to 1.5 atm (Fig. 2). Pressure 

 is monitored by a gauge before the y junction and at the entrance 

 and exit of the condenser tubes. 



Experimental Design 



Although the invertebrates Gammams tigrinus, Chaoboms sp., 

 and Daphnia magna have also been tested, only experiments with 

 striped bass and carp larvae are described here. They were chosen 

 because of their availability and their susceptibility to entrainment 

 and because they represent species with contrasting physiologies. 

 Carp are eurythermal physostomes (with open swim bladders), and 

 striped bass are more stenothermal and are physoclists (with closed 

 swim bladders). Carp were wild spawned, and striped bass were 

 hatchery spawned. Both species were hatched and reared in quarry 

 water from Verplanck, N. Y., the same water supply used during 

 simulator operation and in larval holding facihties. 



For each simulator run at least 60 organisms were placed in and 

 passed through the simulator and held in the collection net for 5-min 

 total exposure. The split flow divided the organisms to each 

 condenser loop. The frequency distribution of the ratio of organ- 

 isms collected from each tank was a normal approximation of the 

 binomial distribution (P = 0.5 and o: = 0.05). 



For all experiments duplicate sets of 30 larvae were counted and 

 placed in flow-through holding containers as absolute controls. They 

 indicated overall mortality in the population and mortality from 

 handling and observational stress. Static "barrel" controls, consisting 

 of 30 organisms placed in flow-through containers suspended in each 

 collection tank, were run in all experiments. These groups were 



