the parent experiment was terminated, weights of survivors of either sex 

 in the treatment chambers did not differ significantly from weights of 

 control fish (Table 3). 



Fathead Fi Generation 



Survival of fry in the F^ generation after 28 days was generally 

 higher than in the parent experiment. Survival averaged 84 percent in 

 the three controls and ranged from 88 percent at 26.3 ug/liter HCN to 36 

 percent at 81.0 ug/liter HCN (Table 4). Mortality rate and HCN concentra- 

 tion were not significant correlated at the 0.05 level. Over the period 

 of 28 to 56 days, all chambers had 81 percent survival or higher. Mean 

 length of fish in treatments after 28 days ranged from 116 to 64 percent 

 of that in controls. The fish at 26.3 ug/liter were significantly longer 

 than control fish, and those exposed to treatment of 34.8 ug/liter and 

 greater were significantly shorter than control fish. 



Mean total lengths of fish in treatments after 56 days ranged from 

 105 to 81 percent of mean length in controls, and mean weights ranged 

 from 122 to 52 percent of that in controls (Table 4). Weights and lengths 

 of fish in treatments from 5.7 to 52.2 ug/liter were not significantly 

 different than controls. Mean lengths and weights of fish at 61.6, 70.5, 

 95.9 and 105.8 ug/liter were significantly different than controls. 



Brook Trout - Adults 



Survival and Growth- 

 Adult brook trout were subjected to various levels of HCN for 196 

 days and showed no significant mortality or growth differences (p>0.05) 

 associated with cyanide concentration. In treatments of 53.9, 64.9 and 

 75.3 ug/liter HCN, one fish died in each after temperature was reduced to 

 9 °C. In the two highest treatments fish showed increased irritability 

 when temperature was reduced. 



Spawning and Egg Production- 

 Spawning started in controls and at 5.7 ug/liter HCN 145-147 days 

 after treatment started, but at higher treatments, spawning did not start 

 until 156-159 days after treatment began (Table 5). The number of eggs 

 deposited per 100 grams of female varied from 357 in one control to 106 

 at 75.3 ug/liter HCN (Figure 2). The number of fertilized eggs per 100 

 grams of female varied from 293 in one control to none at 64.9 ug/liter 

 HCN. The percentage of live eggs 12 days after hatching varied from 93.6 

 percent of fertilized eggs in the control to 64.1 percent at 53.9 ug/liter 

 HCN and percent at 64.9 ug/liter. Sperm mobility was tested at 11 HCN 

 concentrations but no significant relationship (p>0.05) with HCN was 

 noted. 



Egg Survival and Hatch- 

 Eggs were incubated and alevins held for 90 days at HCN concentrations 

 of 5.6 to 77.2 ug/liter at 9 °C and 64-90 percent saturation of oxygen. 

 No significant differences from controls in percentage hatch was observed 

 (Table 6). Survival of alevins for 90 days after hatching were not signi- 



45 



