466 Memoir Sears Foundation for Marine Research 



been suggested furthermore that the presence of parr is a safety factor. The spawning 

 males may fail to get their vent deep enough into the bed to have their sperm fertilize 

 most or all of the eggs. Under such circumstances, the parr are of importance since 

 their sperm, released very close to the eggs, have a good chance of reaching them. 



The number of eggs produced varies with the age and size of the females, as shown 

 in Table i. Menzies has given a range of 600—1000 eggs per pound of spawning female 



Table I. Average Number of Eggs Produced by Canadian Atlantic Salmon* 



, First Spawning After >j Salmon That Have 



2 Years at Sea 3 Years at Sea Spawned Before 



Number of females 503 15 16 



Average weight of female (pounds) ... 10.51 I9-I3 16.68 



Total number of eggs 8,848±68 i3,883±483 I2,3i3±648 



Eggs per pound of fish 834 ±5 723 ±13 738 ±34 



* From Belding {14)- 



{100). Jones and King estimated from the number of eggs recovered from redds made 

 by their nine-pound experimental female that she had laid 700 eggs per pound of body 

 weight {jg). Large females usually have larger eggs than small ones (-T^), but they are 

 fewer (lOO). 



Although Belding found a definite but slight difference in the number of eggs per 

 pound of fish between females of the Miramichi River (817 fish) and coastal females of 

 the Bay-of-Chaleur type (854 fish), this difference was not sufficient to warrant its use 

 in identifying river varieties of Atlantic Salmon at sea (14). 



After being deposited and during incubation, the eggs of the Atlantic Salmon 

 are subject to many vicissitudes, such as being dislodged by other spawning Salmon 

 in overcrowded streams, being washed out by floods, and being frozen in the winter 

 at times of low water. 



Incubation Period. The large, thick-shelled eggs, about 6—7 mm in diameter, de- 

 velop slowly over the winter and hatch in the spring at various times depending on 

 the temperature and on other conditions at the spawning sites. In hatching experiments 

 with eggs from specimens of different ages taken in or close to seven rivers of the 

 three Maritime Provinces of Canada, Belding, et al. (16) found that the date of hatching 

 varied from March 15 to May 4 and that the location of the hatchery in which the 

 eggs were incubated seemed to be an important factor, for it took place on 111/15 at 

 Prince Edward Island, on 111/21 and iv/25 at Middleton, N. S., on iv/ii-19 at Mar- 

 garee, N. S., on iv/20 at St. John, N. B., on iv/23 at Bedford, N. S., on iv/26 at 

 Antigonish, N. S., and on v/2— 4 at Restigouche and Miramichi, N. B. They observed 

 further that the water temperature "between 34 and 4i°F. is not a prominent factor 

 in determining the length of the incubation period," whereas temperatures above that 

 decrease the incubation time markedly; also the water temperature at the end of the 

 incubation period may determine the hatching date, since the temperatures in the early 

 hatcheries were only slightly lower at hatching (35°-38°F) than in the late hatcheries 



