458 



FISHERY BULLETIN OF THE FISH AND WILDLIFE SERVICE 



averages were compared according to 

 spent in each environment as follows: 



seasons 



I (-3.99, P for 0.05=3.75, 4 d. f. 



The significant difference of 298 eggs between 

 fish spending 2 summers at sea and those spending 

 3 summers, but with similar lake histories, is 

 fairly clear evidence that younger ocean-age 

 fish have higher fecundity than older ocean-age 

 sockeye of the same size. The rather consistent 

 difference between 2- and 3-ocean-age fish would 

 also indicate that the ocean environment is 

 relatively stable as the two groups were not at 

 sea during identical yeai's. 



If we now turn the analysis around and note the 

 egg counts for 3- and 4-fresh-water-age fish with 

 identical ocean histories that spend 2 and 3 

 summers in fresh water, the difference in fecundity 

 is neither consistent nor significant. This could 

 be interpreted to mean that fecundity does not 

 differ between fish of 3 and 4 fresh-water ages, 

 but since there are obvious differences between 

 year classes, owing probably to lake conditions, 

 such a conclusion is not fully warranted by these 

 data. What is required are data over a sufficiently 

 long period to discount these fresh-water en- 

 vironmental effects. 



RELATION OF EGG SIZE TO EGG 

 NUMBER 



Surprisingly few records have been published 

 on actual size of ova of Salmonidae, investigators 

 being content to speak of size in a purely compara- 

 tive sense. For instance, Belding et al. (1932, 

 p. 214) say — 



In general the size of the egg depends upon the size of 

 the parent salmon, the larger specimens producing the 

 larger egg. Also, the size of the egg varies with the sal- 

 mon of the different rivers. The material used in this 

 study permits its division into two classes, large and small 

 eggs. There is no relationship between the size of the 

 egg and the length of the incubation period. 



Gilbert (1915, p. 57) also used only a compara- 

 tive measure of size. He says in speaking of 

 British Columbia sockeye, 



A similar difference, but even more pronounced, is found 

 among certain lots of eggs collected by Mr. Stone in 

 Smith Inlet, those from Quey Creek being markedly smaller 

 than those from the Gelulch and Delelah Rivers. It re- 

 quired 74 Quey Creek eggs to fill a tube which would hold 

 only 38 from the Gelulch and the Delelah. 



Perhaps the chief reason for this lack of data on 

 size of ova is that the salmon taken by the 

 commercial fishery are in various stages of egg 

 maturation. Thus, at Karluk River many of the 

 sockeye taken in the fishery may not spawn for at 

 least another month. This is reflected in the 

 weight of sockeye eggs at Karluk ranging from 

 .03 to .095 grams (fig. 4). 



The same late maturation is found in the 

 Atlantic salmon. Speaking of S. salar in Norway, 

 Dahl and S0mme (1944, p. 39) say- 

 In the grilse, which have spent more than a year in the 

 sea, the GW/TW [ratio of gonad weight to total weight] is 

 still practically in the same undeveloped stage in the 

 early part of the season. A gradual development in the 

 relative size of the sexual organs asserts itself as the fish- 

 ing season advances, but the main growth towards matur- 

 ity takes place after the fish have entered the rivers. 



They agree with Belding et al. that the indi- 

 vidual egg size is partially dependent on fish size, 

 saying (op. cit., p. 22), "It is a well known fact 

 that in large salmon the ovaria as well as the 

 single ova arc larger than in salmon of small size." 



Egg size is regarded bj' Svardson (1949, p. 120) 

 as resulting from natural selection. He states — 



Summing up it can be said that the evidence now at 

 hand shows that competition among fry gives the larger 



