Discussion. 



Mk. Ward T. Bowek, Washington, D. C. : The method of measuring 

 eggs referred to is not unlike that devised by Mr. Hector von Bayer, 

 formerly architect and engineer of the Bureau of Fisheries, vphich was 

 reported fully in a publication of the Bureau. It would seem that the 

 same principle is involved. Years ago in my experience at the station at 

 Battle Creek, California, where we handled in one season more than 

 57,000,000 Chinook salmon eggs, it was well known that their average size 

 varied considerably through the season. Several times during the con- 

 tinuance of operations very careful counts of the eggs were made a few 

 hours after they were taken, and a variation of 200 to 300 eggs per quart 

 would be found, the eggs increasing slowly in size as the period of incuba- 

 tion advanced. 



Dr. G. C. Embody, Ithaca, N. Y. : The claim made in this paper is 

 that because the eggs do not vary in size in one particular stream, those 

 eggs came from parents that were hatched there and have returned to that 

 same stream, and that since there is a variation in the three different 

 streams, each having a different size of egg, each must have been pro- 

 duced by parents that were hatched there. Mr. Robertson does not indi- 

 cate here which of the three streams was entered first by the fish, but he 

 says that the larger size of the egg is not due to fuller development in the 

 later spawning fish, for apparently the sockeye which spawns latest in the 

 season has the smallest egg of all of the Pacific coast sockeyes. 



Mr. G. O. Leach, Washington, D. C. : I do not believe that sockeye 

 eggs vary in size as do brook trout eggs, where we find a variation of 

 possibly 300 per ounce. Yes Bay, Alaska, has a run of sockeye salmon 

 that enters the lake along in July, begins to spawn about the first of 

 September, and continues until along in January. There is a consider- 

 able variation in the size of the eggs between the first spawners and those 

 later in the season. The cannerymen in Alaska know the number of 

 salmon from a particular stream required to fill a case, and that this 

 average per case varies little from year to year. I believe it is gener- 

 ally conceded that there is some slight variation in the size of the eggs. 



Dr. D. L. Belding, Hingham, Mass. : This paper is especially valuable 

 in adding one more bit of presumptive evidence in favor of the parent 

 stream theory. I do not believe that we can say absolutely that the 

 measurement of eggs alone proves the parent stream theory, but it cer- 

 tainly offers strong circumstantial evidence. There is little doubt that 

 the alewife or branch herring returns to a particular river to spawn. 

 When there are several branches with separate spawning ponds, there is 

 some question whether fish return to the identical pond where they were 

 hatched. That this specializing' tendency exists has been shown by creat- 

 ing fisheries through planting adult alewives in unfrequented waters to 

 which they return for spawning in three or four years. However, there 

 is also evidence that they do not always return to these particular ponds. 



In 1920 a fishway was installed at the Lawrence dam on the Merrimac 

 River, which for years had formed an impassable barrier to fish. Ale- 

 wives had spawned in certain tributaries and even in the river below the 

 dam, when they could not get to the spawning ponds, and they now ran 



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