rates were better than in 18° or 32°C despite some deaths which 

 occurred in 2, 25, and 36°/ooS. Because of high mortalities it was 

 hard to draw conclusions about the steady-state levels at 18°C in 

 other salinities. The shrimp in 18°C were under heavy stress and 

 experienced a total mortality in 2°/ooS within six hours and a high 

 mortality in other concentrations. In 32 °C conditions apparently 

 the shrimp attained steady-state levels in 5, 10, and 15°/ooS within 

 a day. But as a possible result of the starvation effect there was 

 a steady drop in the oxygen consumption in 36°/ooS from the second 

 day and later in 10 and 25°/ooS; the means showed highly signifi- 

 cant variations with the initial rates (Table 13) . Survival rates 

 at 32°C were poorer than in 25°C, particularly in low salinities. 



Effect of Salinity Change on Respiration 



The metabolic response curves (moving averages) of shrimp accli- 

 mated and tested in 25°, 32°, and 18°C combinations were reproduced 

 in Figs. 109a, b,c, 110a, b,c and llla,b,c, respectively, to show the 

 significance of salinity change on respiration. 



Effect of 25°C acclimation 



Brown shrimp acclimated and tested at 25°C (Fig. 109b) exhibited 

 three levels of respiratory rates in relation to salinity concentra- 

 tions: 



1. Salinity (15°/oo) in which the oxygen consumption was low, 



2. Salinities (2, 5, and 36°/oo) in which the consumption was 

 was high, and 



3. Salinities (10 and 25°/oo) in which the consumption was 

 median. 



The initial low and high oxygen uptake levels in the 15°/oo and 

 36°/ooS media, respectively, continued throughout the test period. 

 In other concentrations some readjustments occurred in the accli- 

 mation process. Significant differences were found in the oxygen 



226 



