2o6 POPULAR SCIENCE MONTHLY. 



small percentage of the year's product for the river. At Battle Creek 

 Hatchery alone that year, 1897-8, there were nearly 50,000,000 eggs 

 taken. There is little migration of the young salmon during the sum- 

 mer months. In August we could account for 94 per cent, of the 

 fry we had marked in one of the pools in July; 76 per cent, in the 

 pool in which they were released, and 18 per cent, in the pool below. 



The growth of the larger fry in fresh water is slow. The average 

 size of the marked fishes in August was 3.91 inches, in September 3.86 

 inches, in October 4.20 inches, in November 4.20 inches, being a total 

 gain of but .29 inch in three months. The earlier rate was .3 inch per 

 month. Another effect of this summer residence in fresh water is the 

 maturing of the male genital organs. A large proportion of the males 

 that remain in fresh water until they reach a length of four inches 

 becomes sexually mature. Its significance is not understood, and its 

 effect upon the future growth of the fish is not known. The number of 

 parasites found in the stomachs of young salmon living in fresh water 

 increases with their size and with the time of year, there being more in 

 the fall than earlier. Their food in fresh water at all ages, seasons, 

 and places is insects, about two thirds being aquatic larvae, and the 

 other third adult insects. 



The Adult. 



As stated above, young salmon reach the ocean when four or five 

 months old. Concerning their habits from that time until they return 

 to fresh water at maturity, we know very little. They are occasionally 

 taken in the ocean near San Francisco, but so rarely as to indicate very 

 little concerning their habits. They are abundant in Monterey Bay 

 during the spring and early summer, but their appearance there is only 

 the first step in their migration up the rivers to spawn. 



The length of their stay in the ocean has been determined with con- 

 siderable certainty by a series of observations carried on recently with 

 the Columbia Biver salmon, which is the same species as the Sacramento 

 salmon. In May, 1896, 5,000 young salmon 2.5 inches long were 

 marked by cutting off the adipose fin, and were released in the 

 Clackamas Biver, a tributary of the Columbia. The eggs from which 

 they were hatched were spawned in September, 1895. During the sum- 

 mer of 189'8, a little over two years after the marking, and a little less 

 than three years after the spawning of the eggs, 375 of the marked 

 salmon were taken in the Columbia, and five were taken in the 

 Sacramento Biver in California. A few more were taken both in the 

 Columbia and in the Sacramento in 1899, and again in 1900. The 

 size of those taken in 1898 varied from 10 pounds to 57 pounds. 



Besides indicating the age of the spawning salmon, this experiment 

 shows that most salmon return to the river through which they reached 

 the ocean. They do not do this because it is the stream in which 



