FISHERY BULLETIN: VOL 78, NO. 3 



o 



o 



S 5.00 



I- 3.00 



U 



ECCS 

 HATCHED 



125 150 175 



DAYS AFTER FERTILIZATION 



FRY 



EMERGED 



1///////M 



L 



Figure 3. — ^Total ammonia production per individual pink salm- 

 on egg or alevin in the three gravel incubators seeded with 6,400 

 eggs. Ninety-five percent confidence limits for the periodic means 

 were calculated using the error mean square from a one-way 

 ANOVA for sampling periods. Horizontal bars show when eggs 

 hatched and fry emerged. 



z 

 > 



LU 

 < 



o 



o 

 u 



01 5 



z 

 o 



V- 



u 



D 

 O 

 O 



a: 



z 

 o 



< 



5i 



DAYS AFTER 

 FERTILIZATION 



r 



ECCS- 



1600 



SEEDING DENSITY, 



6100 

 ECCS PER INCUBATOR 



12,800 



Figure 4. — ^The effect of seeding density on individual ammonia- 

 production rates during development of eggs to emerging alevins. 

 Total ammonia was measured in incubator effluents cmd was cor- 

 rected for emergence from the incubators. Eggs hatched 100-120 

 days after fertilization, and alevins from 1,600-egg density 

 emerged about 203-220 days after fertilization. 



vidual egg or alevin in the incubators on their 

 seeding densities was significant (P<0.01). The 

 average rate of total ammonia production in each 



652 



incubator was the mean of 22 periodic rates mea- 

 sured as the eggs developed into emergent fry. 



DISSOLVED OXYGEN 



Dissolved oxygen concentration in the supply 

 water declined gradually from 9.16 mg/1 (70% 

 saturation) on 14 December 1971 (day 89), about 2 

 wk before the eggs hatched, to 8.08 mg/1 (62% 

 saturation) on 11 April 1972 (day 208, Figure 5). 

 This decline was normal because the lake source is 

 usually covered with ice in winter. 



Generally, as the eggs developed into fry, dis- 

 solved oxygen concentrations in the seeded in- 

 cubators decreased more in incubators seeded 

 with more eggs (Figure 5), except in the incubator 

 with 25,600 eggs. In the incubator seeded with 

 25,600 eggs, massive early emergence of fry left 

 fewer alevins in the incubator than in the in- 

 cubator initially seeded with 12,800 eggs. After 

 the early emergence in the incubator initially 

 seeded with 25,600 eggs, the effluent of the in- 

 cubator with 12,800 eggs had the lowest dissolved 

 oxygen concentration of the study — 3.8 mg/1 dis- 

 solved oxygen (29% saturated) on 7 March (day 

 173). 



Generally, oxygen consumption per egg or ale- 

 vin increased steadily during development. At 7-d 

 intervals during incubation, we estimated oxygen 

 consumption rates in each of the three incubators 

 seeded with 6,400 eggs (Figure 6) and averaged 

 these rates. The average rate of oxygen consump- 

 tion about 2 wk before hatching was about 0.003 



9 6 



y 5 



o 



"<! 3 



25.600 



ECCS 

 HATCHED 



FRY 

 EM ERGED 



— I — 

 100 



125 150 175 



DAYS AFTER FERTILIZATION 



—I — 

 200 



Figure 5. — Dissolved oxygen concentration in hatchery water 

 supply (0 eggs) and in effluents from incubators seeded with indi- 

 cated numbers of pink salmon eggs, December 1971-April 1972. 

 Horizontal bars show when eggs hatched and fry emerged in the 

 incubator seeded with 1 ,600 eggs. 



