1 86 The Life Story of the Fish 



could be identified when caught again. They have "tagged" 

 them with numbered metal plates or plastic disks so that 

 individual fish could be identified when met with later. They 

 have studied their metabolism and their birth rate and their 

 growth rate. The result is that the natural history of the 

 Atlantic and Pacific salmon is better known than that of any 

 other fish, and what is set forth in the following paragraphs 

 has a mathematical certainty about it which cannot often be 

 attained in biological matters. 



Aside from the essential difference in survival after spawn- 

 ing, the Atlantic and Pacific species lead quite similar lives. 

 Both hatch out of eggs buried from five to ten inches under 

 the gravel in the shallow, swift, upper reaches of streams. 

 Both live for a certain length of time in these rivers. The 

 pink salmon and the chum salmon of the Pacific stay only 

 a few weeks, the others may remain anywhere from a few 

 months to as much as three years, and this period varies not 

 only between species, but also within each species, depending 

 on the conditions and on the individual. All grow slowly 

 during river life, few reaching a length of more than six 

 inches in fresh water. All eventually go to sea, and there 

 grow at a tremendously accelerated rate due to the enor- 

 mously greater amount of food available. The record is held 

 by an English fish which, according to the data, gained 27 

 pounds between May, 1905, and August, 1907 — at the rate 

 of a pound a month. The Pacific salmon rarely grow so fast. 



Some of the Atlantic fish, especially the males, return to 

 fresh water to spawn after only a few months at sea. They 

 are still small, and are what the English call "grilse." Most 

 of them remain longer in the sea, some being six or even 

 seven years old on their first return. Such fish have had a 

 chance to eat on a gargantuan scale, and it is probable that 

 all very large individuals are in this category. Of the Pacific 

 salmon, the pink all return at the end of their second year 



