10 



fish were transferred from the aquaria to darkened glass 

 test bottles, in seconas, by gently pouring them onto a plastic 

 screen to remove water and then pouring them through a funnel made 

 from a piece of plastic screen into the bottle. Five fish were 

 put into 525-ral bottles anu 10 to 20 fish in l^OSO-ml bottles. 

 The bottles were sealed and immersed on their sides in a darkened 

 constant-temperature bath. In any one experimental trial, 

 concentrations of fish were identical and are noted in the RESULTS. 



Before fish were added, the bottles were filled with Cultus 

 Lalce water dravm from a 30-liter aquarium which was aerated for 

 30 mln to bring it to equilibrium. Chlorinated catechol was added 

 to bottles from a well aerated 25-ppm stock solution. No 

 chlorinated catechol was added to bottles meant for control fish. 

 In addition, two blanlc samples containing water only and two 

 reagent blanks containing water and chlorinated catechol were 

 treated similarly to those bottles containing fish. 



iifter the 5-hr test period, water was siphoned from each test 

 bottle into a 300-ml bOD bottle and dissolved oxygen was measured 

 by the Azide modification of the Winkler method (Standard Methods, 

 1965). Comparison of dissolved oxygen in reagent and sample blanks 

 at the end of the test with dissolved oxygen in the aqioarium at the 

 start indicated no change in oxygen concentration had occurred. The 

 difference between dissolved oxygen in blanks anu that in controls 

 or experimental bottles was the amount of oxygen used by the fish 

 and usually varied ^^etween 1 and 2 ppm. riespiration rate was 

 calculated as the milligrams of oxygen utilized per hour per graia 

 of dry weiglit of alevin body or fry. itelative respiration rate was 

 the ratio of respiration rate of experimental to control fish. 



Fish were preserved m 10 per cent formalin upon completion of 

 each experiment. Alevin bodies were separated from yolks by careful 

 dissec'.ion before being weighed. Fry, alevin bodies, and yolks were 

 dried at 98°C for 24. hr and dry v/eights were determined on an 

 automatic analytical balance accurate to 0.01 mg. 



