FISHERY BULLETIN: VOL. 70, NO. 2 



1 2.00 r 



10 



20. 

 TIME 



30. 40. 



( MIN.) 



Figure 1. — Nitrogen excretion by 10 specimens of En- 

 graulis mordax in experiment 2. Specimens were fed 

 30 min before experiment. 



ammonia, urea, and creatine accounted for ap- 

 proximately 82.7, 16.0, and 1.3Sr, respectively, 

 of the sum of the ammonia, urea, and creatine 

 values. This sum was approximately 82% of 

 the total nitrogen released. The fish used in 

 the E. mordax experiments 1 and 2 had a mean 

 wet weight of 13.9 g and a mean dry weight of 

 3.9 g per animal; those used in the third exper- 

 iment had mean wet and dry weights, respectiv- 

 ly, of 15.2 g and 4.3 g per animal. 



In the E. ringens experiments, the sum of the 

 individually measured nitrogen compounds ac- 

 counted for 69 to 96 9*^ of total nitrogen excreted. 

 Relative amounts of ammonia, urea, and creatine 

 averaged 44.6, 14.5, and 21.4%, respectively, 

 while 19.5% was unidentified. Although the 

 specimens of E. ringens appeared in good health 

 for the first few hours after capture, their condi- 

 tion deteriorated rapidly after the experiment 

 began. One lived for 83 min, another for 85 min, 

 and the third for 105 min. The behavior pat- 

 tern was a panic response in which the animals 

 tried repeatedly to swim downward into the bot- 

 tom of the container and eventually did consider- 



able damage to their heads, resulting in broken 

 blood vessels in their eyes and nasal regions. 

 The dorsal coloration changed from a greenish- 

 grey to jet black during the deterioration, and 

 once an animal locked into this behavior pattern 

 there was apparently no way to reverse it and 

 death was inevitable. The mean wet weight and 

 dry weight per fish for these experiments was 

 7.0 and 1.9 g, respectively, and nitrogen was 

 found to be 10.9% of dry weight. 



The results for the T. symmetriciis represent 

 a single value for both fish in the same chamber. 

 Prior to, during, and in the 20 hr after the ex- 

 periment the fish swam about the chamber in 

 a calm manner. The wet weight of the sacri- 

 ficed fish was 190.0 g. 



DISCUSSION 



The fish in the E. mordax experiment 2 were 

 the most recently fed, and Figure 1 shows that 

 urea, ammonia, and creatine were released at 

 approximately constant rates over the experi- 

 mental period. Table 1 shows that these release 

 rates for ammonia, urea, and the amm.onia-urea 

 ratio were the highest of all the E. mordax ex- 

 periments. The urea release rates for the other 

 experiments (1, 3a, and 3b) were all similar, 

 but the ammonia release rates and the ammonia- 

 urea ratios appear to be related to the length of 

 the starvation period. 



For the E. mordax experiments, the statistical 

 tests indicated that the ammonia release rates 

 in experiments 1 and 3a and in experiments 

 1 and 3b were not significantly different within 

 each pair with respect to central tendency. On 

 the other hand there were significant differences 

 between the pairs of ammonia release rates in 

 experiments 1 and 2, 2 and 3a, and 2 and 3b. 

 The variabilities for ammonia release rates for 

 all of the experiments were similar. With re- 

 gard to the urea release rates, only those for 

 experiments 1 and 2 were significantly different 

 with respect to location of central tendency and 

 none of the experiments differed from each other 

 with respect to variability. 



These statistics imply that the effect of feeding 

 is rapidly apparent in the ammonia release rates 

 while it appears more slowly and to a lesser de- 



398 



