FECUNDITY OF NORTH AMERICAN SALMONIDAE 



461 



dently ascribed to egg size if we consider the data 

 on weight of fry in conjunction with that of egg 

 diameter (see appendix table 6). Thus, the sac 

 fry of 0. tshaioytucha weiglied 2.9 times the upper 

 limit given for Salmo salar. 



There is general agreement that, within the 

 genus OncorhynchuK, the largest eggs are found 

 in lahawytscha and the smallest in nerka. O'Malley 

 (1920) gives the following number of eggs of each 

 species required to fill a hatchery basket: 



Species: Thousands of eggs 



0. tshawytscha 20-30 



0. kisutch 30-35 



C. keta 33-38 



O. gorbuscha 40-50 



0. nerka 50-60 



Bean (1893, p. 30) says of the pink salmon, 

 0.<j<vhu,tcha, "The eggs are larger than those of the 

 red salmon [0. nerka], but smaller than king 

 salmon [0. tshawytscha] eggs and not so bright 

 red." 



It is not surprising that there is some disagree- 

 ment concerning the relative size of the eggs of 

 kisutch, keta, and gorbuscha since, as we have seen, 

 there is considerable difference between localities 

 in regard to average number within the same 

 species. Only accurate measurements of fully 

 mature eggs from several localities, preserved in 

 the same manner, can be relied upon to show 

 the size ranges in eggs of the various species. 



RELATION OF EGG NUMBER TO 

 LATITUDE 



In order to determine whether there is any 

 relation between fecundity and latitude we have 

 constructed table 3, showing the average fork 

 length and egg number for species of Oncorhynchus 

 arranged geographically from south to north. 

 The averages are shown in figure 8 with the 

 southernmost locality for each species in black. 

 The egg number of four of the species is liigher 

 than expected for the average length in the 

 most southern locality. 



If further research should prove that there is 

 a valid tendency for higher fecundity toward 

 the south, this may possibly be ascribed to the 

 difl'erence in growth rates. This follows because 

 the average age at maturity of all of the species 

 (except gorbuscha) tends to increase toward the 

 north. We have already shown that at Karluk 



the sockeye spending 2 years at sea have a higher 

 fecundity than sockeye of the same length spend- 

 ing 3 years at sea. 



Table 3. — Egg number and fork length in species o/ Oncor- 

 hynchus, arranged geographically from south to north 

 (Includes only samples of more than 20 fish] 



1 Scott Creek omitted, as averages (appendix table 1) were read from re- 

 gression curve. 



— 5 

 CO 



Q 



z 

 < 



CO 



r> 

 o 



X 



CO 



CO 

 CD 

 UJ 



U_ 

 O 



tr 



LU 



m 



O - 0. NERKA 



A - 0. KISUTCH 



<J) - 0. GORBUSCHA 



2 -0 KETA 



D -0 TSHAWYTSCHA 



♦*^ 



50 



60 



70 



80 



90 



FORK LENGTH (CM.) 



Fini'RE 8. — Rchition of mean egg number to mean fork 

 length in species of Oncorhynchus, by locality. South- 

 ernmost localities are shown in solid black for each 

 sjiecies. 



