19 



Scvaral respiration rate measurements were made using alevins 

 dug from the natural spawning ground at Cultus Lake. At 0,75 and 

 O.4.C ppm of tetrachlorocatechol, relative respiration rates were 

 1.51 and 1.03, respectively, in Trial B (TiiBLE 5). Two alevins 

 died at 0.75 ppm tetrachlorocatechol in Trial C. These were the 

 only mortalities associated with measurements ox respiration rate 

 and probably occurred because 0.75 ppm was near the lethal level 

 for sockeye alevins. Relative respiration rates at 0.55 and 0.30 

 ppm tetrachlorocatechol were 1.17 and 1.02, respectively in Trial C. 



Alevins from Trial C were retested the following day in Trial 

 D except that conditions were reversed. That is, control alevins 

 from Trial G were tested at 0.55 ppm tetrachlorocatechol after 

 overnight exposure to that concentration, whereas those alevins 

 subjected to tetrachlorocatechol in Trial C were held in fresh 

 water and served as controls in Trial D. The Trial G control 

 alevins showed a 29 per cent increase in respiration rate when 

 tested in 0.55 ppm tetrachlorocatechol in Trial D (2.712 versus 

 2.096). r'urthermore , alevins transferred to fresh water from 

 tetrachlorocatechol for Trial D had an average respiration rate 

 similar to that for controls on the previous day (2.036 versus 

 2.096), indicating apparent return to normal respiration. 

 Gomparison of average respiration rate of the alevins tested at 

 0.30 ppm tetrachlorocatechol in Trial C (2.L40) with their average 

 respiration rate in fresh water the following day (1.998) indicated 

 respiration rate under experimental conditions was seven per cent 

 greater than under control conditions. A similar comparison with 

 alevins at 0.55 ppm tetrachlorocatechol indicated respiration rate 

 under experimental conditions (Trial C) was I6 per cent g-reater 

 (2.455 versus 2.118) than under control conditions (Trial D) . 



Average relative respiration rates of naturally spawned alevins 

 were calciilated for each tetrachlorocatechol concentration from 



