u 



TABLii] 3 - Acute toxicity of dichlorocatechol to sockeye and pink 

 salmon expressed as 96-hr median tolerance limit (96-hr TL ). 



The difference between those concentrations of di- and 

 tetrachlorocatechol causing 100 per cent mortality in 96 hr and 

 those causing little or no mortality was small, x^or example, 1.0 ppm 

 tetrachlorocatechol killed 100 per cent ox freshly hatched sockeye 

 alevins while none were killed at 0.5 ppm. In addition, all advanced 

 pinlc salmon alevins were killed at 0.375 ppm tetrachlorocatechol, 

 while only 20 per cent succtuabed at 0.25 ppm and all survived at 

 0.175 ppm. Similarly, 3.0 ppm dichlorocatechol killed 90 per cent 

 of sockeye fry (42 mm fork length) vjhile none were killed at 2.5 ppm. 

 Fifty per cent of advanced pink alevins were killed at 2.0 ppm 

 dichlorocatechol but none lied at 1.0 ppm. 



