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



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FiGLTRE 1. — Incubation temperature of pink 

 salmon eggs from fertilization, 16 September 

 1971 (day 0) until termination of the experi- 

 ment, 28 April 1972 (day 2251 after fry emerged 

 from the incubators. Horizontal bars show 

 when eggs hatched and fry emerged from the 

 incubator seeded with 1,600 eggs. 



FRY 

 EMERGED 



wimiiin 



_l I 1—1 L-l_ 



I    



_l l__l i__l I 1- 



75 100 125 150 



DAYS AFTER FERTILIZATION 



175 



200 



November (day 61). It remained near 3.6° C from 

 16 November 1971 until termination of the exper- 

 iment on 28 April 1972 (day 225). The daily tem- 

 perature variation was <0.2° C. 



During the incubation period, pH of the hatch- 

 ery water supply changed little (pH, 6.13-6.39). 

 Effluents of incubators with eggs had a pH from 

 6.08 to 6.36. Effluent from the incubator with the 

 highest density of eggs (average pH, 6.19) was 

 more acidic than the hatchery supply (average pH, 

 6.27). 



Concentrations of total ammonia in effluents 

 were higher in seeded incubators than in control 

 incubators and generally increased with more 

 eggs (Figure 2). Concentrations of total ammonia 



ECCS HATCHED ^2, 



mmmmmA 



FRY EME RGED 



100 125 150 



DAYS AFTER FERTILIZATION 



Figure 2. — Concentrations of total ammonia in hatchery water 

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

 dicated numbers of pink salmon eggs. Horizontal bars show when 

 eggs hatched and fry emerged in the incubator seeded with 1,600 

 eggs. Peak total ammonia concentration for each seeding density 

 is indicated numerically. 



in the effluent from control incubators and in the 

 water supply were nearly identical (maximum 

 concentration about 0.011 mg/1). During the 

 study, maximum concentrations of total ammonia 

 in seeded incubators ranged from 0.03 mg/1 for the 

 incubator seeded with 1,600 eggs (March) to 0.32 

 mg/1 for the incubator seeded with 25,600 eggs 

 (January). 



The rate of total ammonia production per indi- 

 vidual was periodically measured in all of the in- 

 cubators. As development progressed from the 

 eyed-egg stage to the emerging fry stage, rate of 

 total ammonia production per individual in- 

 creased. For example, in the three incubators 

 seeded with 6,400 eggs (Figure 3), the mean of 

 total ammonia production 3 wk before hatching 

 (89 d after fertilization) was <2 x 10 "* mg/h per 

 egg. By hatching (110 d after fertilization), the 

 mean of total ammonia production increased to 

 nearly 4 x 10"^ mg/h per egg. At emergence, ap- 

 proximately 14 wk after hatching (208 d after fer- 

 tilization), the mean of total ammonia production 

 was almost 6 x 10 ■* mg/h per alevin. 



The rate of total ammonia production per egg or 

 alevin increased with seeding density (Figure 4). 

 The rates of total ammonia production per indi- 

 vidual were meaningless for the incubator with 

 25,600 eggs (not shown in Figure 4) because many 

 of the eggs and alevins had died and were decom- 

 posing and because many of the alevins had 

 emerged 30-60 days early. At the other three seed- 

 ing densities (1,600, 6,400, and 12,800 eggs), the 

 rates of total ammonia production were higher at 

 higher seeding densities, and the regression of av- 

 erage rates of total ammonia production per indi- 



651 



