merits. Between 28 and 56 days, survival was 80 

 chambers. Survival was 95 percent or greater in 

 and 84 days (Table 2). Mortality rate in these 

 significantly correlated with HCN concentration 

 56 days exposure, the mean weight of fish in the 

 130 to 65 percent of that in controls, and from 

 weight in controls after 84 days. The length of 

 HCN exposure to the onset of spawning averaged 1 

 ranged from 148 to 206 days in treatment chamber 

 spawning begin significantly earlier or later th 



percent or greater in all 

 all chambers between 56 

 two periods was not 

 at the 0.05 level. After 

 treatments ranged from 

 128 to 86 percent of mean 

 time from the start of 

 56 days in controls, and 

 s. In no treatments did 

 an in the controls. 



Mean egg production and egg production per ferna"^ in each chamber are 

 shown in Table 3. Egg production per female in treatments ranged from 72 

 percent of that in controls to zero (Table 3). Egg production per female 

 was significantly reduced relative to controls in HCN treatments of 19.6 

 yg/liter and higher. Mean percentage hatch of eggs spawned and incubated 

 in the tests (Table 3) ranged from 83.9 percent in controls to 21.6 per- 

 cent at 63.6 pg/1 iter and percent at 80.7 yg/liter (Figure 1). When 







10 



20 30 40 50 60 

 HCN CONCENTRATION, ptg/l 



70 



Figure 1. Number of fry produced per 100 grams of female fathead minnow 

 in HCN. Egg production times percentage hatch. 



42 



