22 



10 alevins each at 42°F. Respiration rates of control alevins 

 were 0.110 and 0.183 mg/hr/gm while respiration rates of alevins 

 at 1.5 ppm dichlorocatechol were 0.189 and 0.198 mg/hr/gra. The 

 average relative respiration rate was calculated as 1.32 from 

 these data. Thus it is seen that dichlorocatechol also caused 

 an increase in respiration rate but required a concentration 

 which was approximately three times as great as that of 

 tetrachlorocatechol to produce the same response. 



Sockeye Salmon Fry 



Meas-urements of respiration rates of sockeye fry were made 

 at tetrachlorocatechol concentrations between 0.05 and 0.40 ppm 

 in an attempt to define the minimum concentration at which 

 tetrachlorocatechol would affect respiration. Respiration rates 

 of the two control groups of fry varied widely bc;tween 1.165 and 

 1.940 mg Op/hr/gm (TiiBLE 6). Except for one group, the respiration 

 rates of experimental fry were between those for the two control 

 samples. This condition arose, it is believed, from variation in 

 activity of fry in the bottles. Observations of fry held in 

 conditions similar to those in the experiment, except that light 

 was not excluded, indicated that degree of activity was independent 

 of sublethal concentrations of tetrachlorocatechol but was influenced 

 by activity of individual fish. For example, in some of the control 

 and experimental bottles, a single fry swam vigorously much of the 

 time and this seemed to increase the general level of activity in 

 the group. As a result, fry in some bottles were undoubtedly more 

 active than in others ana this difference in activity would have 

 caused variations in oxygen consumption unrelated to tetrachlorocatechol 

 concentration (Brett, 1962) . 



The average relative respiration rates weru 1.04, 1.27 and 1.05 

 for fry hold overnight in tetrachlorocatechol and tested at 0.2, 0.1 

 and 0.05 ppm, respectively (T^Lt, 6). For fry held overnight in water 

 only, respiration rates measured in tetrachlorocatechol were 1.13 and 



