Group comparisons were made by covariance analysis of log-transformed 

 data (Snedecor and Cochran, 1967) . Sex influence on respiration rates 

 was tested by covariancel analysis for each species when possible. Data 

 from males and females were combined for comparisons of base-line and 

 experimental values. 



3. Results . 



a. Striped Bass . Fish were held at approximately 15° Celsius and 5 

 parts per thousand salinity for a minimum of 3 days before respiration 

 rates were determined. Oxygen consumption rates were determined at three 

 swimming speeds--0. 28, 1.02, and 1.58 ft/s. 



In filtered water, a 50-gram fish swimming at 0.28 ft/s consumed 19.0 

 milligrams oxygen per hour (mg O2 h"-^) and a 150-gram fish used 31.4 

 mg O2 h"l. At a speed of 1.02 ft/s, a 50- and a 150-gram fish used 24.3 

 and 41.3 mg O2 h"-^, respectively. At speeds of 1.58 ft/s, oxygen consump- 

 tion rates increased to 33.7 mg O2 h~^ for a 50-gram fish, and 63.7 

 mg O2 h"-^ for a 150-gram fish. A significant increase in respiration rates 

 was observed between measurements made at 0.28 and 1.02 ft/s and between 

 1.02 and 1.58 ft/s (Table 11). 'Covariance analysis showed that oxygen 

 consumption rates of male and female fish did not differ at either swimming 

 speed (Table 12). Covariance analysis was not made for swimming speeds of 

 1.58 ft/s due to the small number of females tested. 



A 50-gram fish consumed 19.2 mg O2 h"-^ and a 150-gram fish consumed 

 37.8 mg O2 h"-^ at a swimming speed of 0.28 ft/s during exposure to 0.79 

 g 1"-^ fuller's earth. A 50- and a 150-gram fish swimming at 1.02 ft/s 

 under these conditions consumed 24.1 and 41.2 mg O2 h"-^, respectively 

 (Figs. 7 and 8; Table 13). Striped bass swimming at 1.58 ft/s in fuller's 

 earth suspensions consumed less oxygen than fish swimming at that speed 

 under base-line conditions (Fig. 9; Table 13). Oxygen consumption was 

 uniformly depressed by about 25 percent throughout the weight range studied. 



A graph of the oxygen consumption rates of striped bass swimming at 

 0.28 and 1.02 ft/s during exposure to 0.79 g 1'-^ fuller's earth showed 

 different slopes. Respiration rates at swimming speeds of 1.02 and 1.58 

 ft/s during this exposure were not different, Rates for fish swimming at 

 0.28 and 1.58 ft/s were different at the 1-percent level (Table 11). Oxy- 

 gen consumption rates of male and female striped bass swimming at 0.28 

 and 1.02 ft/s in fuller's earth suspensions were not different (Table 12). 

 Comparisons of male and female oxygen consumption rates at 1.58 ft/s could 

 not be made because too few females were studied. 



Striped bass held at 22.5° Celsius and 9 parts per thousand salinity 

 were tested at swimming speeds of 1.05 and 1.58 ft/s under base-line con- 

 ditions and during exposure to natural sediment suspensions. The experi- 

 mental procedure was modified because increased temperature, salinity, and 

 sediment-oxygen demand reduced dissolved oxygen. The 3-hour acclimation 

 period at a swimming speed of 0.28 ft/s was changed to 3 hours at 1.05 ft/s 



32 



