TEE SACRAMENTO SALMON. 205 



salmon. In the vicinity of Sims in 1898 we found 700 to 1,000 in the 

 various pools. They were common in McCloud Eiver in September, 

 and in Fall Eiver in August. 



These summer residents, as they may be called, are confined to the 

 headwaters, the clear streams with rocky bottoms. They do not stay 

 much of the time in the swift current or riffles, but remain in the more 

 quiet pools, where they feed on insects and take the angler's fly the same 

 as trout. Considerable effort was made to learn as much as possible 

 concerning them, and Sacramento Eiver near Sims and its tributary, 

 Hazel Creek, were visited each month from May to December with that 

 end in view. 



During July and August, all specimens taken were marked by 

 cutting off the adipose fin, by which means we were able to make esti- 

 mates of the number in the pools, their rate of migration, and their 

 rate of growth. The number estimates were made thus: After 

 having marked a few and released them in the pool, the following pro- 

 portion was formed with the data from each seine-haul : the number of 

 marked fry taken is to the number of marked fry in the pool, as the 

 total number taken is to the total number in the pool. In August, 

 when we could distinguish those just marked from those marked in 

 Julv, we were able to make estimates of the number of Julv-marked 

 fry in a pool and, knowing the number released there in July, to com- 

 pute the rate of migration for the month. 



The following table gives the result of the work in one pool, and 

 illustrates the data used in making the number estimates : 



The average estimates for two other smaller pools are 685 and 861. 

 From these estimates it seems probable that there were about 10,000 

 young salmon to the mile in the upper Sacramento during the summer 

 of 1898, or less than a million in all the headwaters, which is a very 



