BAILEY ET AL.: EFFECTS OF SEEDING DENSITY OF PINK SALMON 



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DAYS AFTER FERTILIZATION 



Figure 6. — Oxygen consumption per individual pink salmon egg 

 or alevin in three gravel incubators seeded with 6,400 eggs. Ninety- 

 five percent confidence limits for the periodic means were calcu- 

 lated using the error mean square from a one-way ANOVA for 

 sampling periods. Horizontal bars show when eggs hatched and 

 fry emerged. 



mg/h per egg; by hatching, oxygen consumption 

 increased to about 0.010 mg/h per alevin. The 

 transient peak of oxygen consumption at the end 

 of hatching is probably associated with increases 

 in metabolism due to increases in activity during 

 the hatching process and activity of alevins as 

 they redistribute themselves within the incubator. 

 These transient increases during hatching would 

 have been more significant if the large numbers of 

 eggs in the incubators had hatched synchronously 

 over a day rather than over a 2-wk period. By the 

 time of emergence, oxygen consumption had in- 

 creased to a mean of 0.027 mg/h per alevin in the 

 incubators seeded with 6,400 eggs. In the in- 

 cubators seeded with other densities of eggs, oxy- 

 gen consumption per individual also increased as 

 eggs developed into alevins. The increase in oxy- 

 gen consumption by eggs and alevins during 

 development was in response to growth and 

 not in response to increased temperature. Tem- 

 perature remained nearly constant (about 3.6° C) 

 from 2 wk before hatching until all alevins 

 emerged. 



Densities of alevins in the incubators influenced 

 the individual oxygen consumption rates (Figure 

 7 ). Before hatching, the oxygen consumption rates 

 per egg (days 89 and 96 1 were about the same in 

 incubators of different densities. After hatching 

 and to the time approaching emergence (days 117, 

 152, and 173, Figure 7), oxygen demand by indi- 

 vidual alevins increased with increased seeding 

 density (excluding the incubator with 25,600 

 eggs). The incubator seeded with 25,600 eggs (not 



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-DAYS AFTER FERTILIZATION 



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1,600 6.U00 



SEEDING DENSITY, EGGS PER INCUBATOR 



12,800 



Figure 7. — The effect of seeding density on individual oxygen 

 consumption rates during development of eggs to emerging 

 alevins. Oxygen measurements were taken from incubator 

 effluents and corrected for emergence to milligrams/ alevin per 

 hour. Eggs hatched 100-120 days after fertilization, and alevins 

 from the 1,600-egg density emerged about 203-220 days after 

 fertilization. 



shown in Figure 7) contained a large number of 

 dead eggs and alevins, which were decomposing. 

 As emergence approached (days 201 and 208), 

 oxygen consumption per alevin did not tend to 

 increase with alevin density. 



The increased production of ammonia and con- 

 sumption of oxygen by alevins with increased 

 seeding densities indicate increased metabolic 

 rates caused by more frequent stimulation and 

 interaction of neighboring alevins. 



QUANTITY AND QUALITY OF 

 FRY PRODUCED 



Egg-to-Fry Survival and Time of Emergence 



Survival from eyed eggs to fry in the incubator 

 seeded with 25,600 eggs (50%) was markedly 

 lower than survival in all other incubators ( ^92% , 

 Table 1). Survival was almost 100% in the in- 

 cubator seeded with 12,800 eggs; the incubator 

 seeded with 12,800 eggs produced almost as many 

 live fry as the incubator seeded with 25,600 eggs. 

 Survival in the incubators seeded with 1,600 eggs 

 and 6,400 eggs ranged from 92% to 100%. 



Alevins emerged markedly earlier from in- 

 cubators seeded with >6,400 eggs (Figure 8). If the 



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