FISHERY BULLETIN: VOL. 78, NO. 3 



time of50% emergence in the incubator with 1,600 

 eggs is used as a standard, 50% of the fry in in- 

 cubators seeded with 6,400 eggs emerged on the 

 sameday (15 April, day 212); 50% of the fry in the 

 incubator seeded with 12,800 eggs emerged 7 d 

 early (8 April, day 205); and 50% of the fry in the 

 incubator seeded with 25,600 eggs emerged 82 d 

 early (24 January, day 130). 



150 175 



DAYS AFTER FERTILIZATION 



225 



FIGLTRE 8. — Effect of seeding density on daily cumulative per- 

 centages of emergence of pink salmon fry from gravel incubators, 

 December 1971- April 1972. Horizontal bars show when eggs 

 hatched and fry emerged from incubator seeded with 1 ,600 eggs. 

 Number beside each line is the number of eggs seeded in each 

 incubator. 



Size of Fry and Stage of Development 



In the incubators with seeding densities above 

 6,400 eggs, fry emerged earlier and were shorter, 

 lighter, and less developed (higher Kq ) than fry in 

 incubators with lower seeding densities. 



During the time we monitored emergence, ale- 

 vins emerging from the incubator seeded with 

 25,600 eggs were substantially smaller than ale- 

 vins emerging from the other incubators. At 50% 

 emergence, the alevins in the incubators seeded 

 with 25,600 eggs were in an earlier stage of devel- 

 opment (higher A'q) (Figures 9-11) than alevins in 

 other incubators. 



Analysis of variance of average lengths of fry at 

 the three lower seeding levels — 1,600, 6,400, and 

 12,800 eggs — indicated significant and changing 

 differences (P<0.001), i.e., interaction, in fry 

 length among seeding densities and sampling 

 times (Table 2, Figure 9). At the first sampling time 

 (about 25% emergence), fry emerging from the 

 incubator seeded with 12,800 eggs were substan- 



25 50 75 



SAMPLING TIME (PERCENTAGE EMERGENCE) 



Figure 9. — Average length of pink salmon fry that emerged 

 from gravel incubators seeded with indicated numbers of eggs. 

 Samples of 50 fry were taken from each incubator when 25%, 

 50%, and 75% of emergence from that incubator had occurred. 

 Bars represent 95% confidence limits. The sample for 25% 

 emergence at the 25,600 density was lost. 



Table 2. — Analysis of variance of average lengths of pink salm- 

 on fry, with variation among seeding levels within sampling 

 times partitioned out. 



•••p-iO.001. 



••p<o.oi. 



ns = not significant. 



tially smaller than fry emerging from incubators 

 seeded with 1,600 and 6,400 eggs. At the second 

 sampling (about 50% emergence), fry emerging 

 from the incubator seeded with 12,800 eggs were 

 still smaller than fry emerging from incubators 

 seeded with < 12,800 eggs, but the difference was 

 not as large as at the first sampling. By the third 

 sampling (about 75% emergence), differences 

 were not statistically significant (P>0.05). 



Analysis of variance of average weights of the 

 same fry from the three lower seeding densities 

 detected differences among seeding densities (Ta- 



654 



