8 THE HABITS AND HAUNTS OF FISH. 



rivers ; but in the event of these failing, the fish often 

 prolong their stay in salt water bays and in the 

 mouths of rivers until the first rising of water will 

 admit of a passage. There are in most salmon rivers 

 numerous weirs so constructed as to render the pas- 

 sage of fish an impossibility, except during a heavy 

 flood. In waters where these artificial obstructions 

 do not exist, migratory fish pass frequently to and 

 fro, these periodic ascents being doubtless occasioned 

 by the quest of food. For a salmon to remain in 

 good condition for a protracted period in fresh water 

 would appear to be an impossibility. Their ova are 

 vivified and their young flourish in the inland streams, 

 but after attaining a given size their growth stops, 

 and they sicken and die if the passage to salt water 

 is obstructed. The cleansing influence of the marine 

 trip is necessary at least every two years, even when 

 the supply of food in fresh water is ample, which is 

 seldom the case. The freshly run fish may be said 

 to be invariably fat, and in the best possible con- 

 dition, not only in the substance of the flesh, but in 

 the large quantities of adipose matter which is found 

 on the pyloric appendages, which secret store serves 

 as an internal source of sustenance supporting the 

 fish during its summer stay in fresh water, where 

 food is comparatively^scarce.^^^^^^^ 



It is often asserted that ariLUlliuiuub fish will not 

 feed except in salt water, and that their internal fat 

 sustains them when absent from it. This is most 

 certainly erroneous, as migratory fish are not more 

 given to fast than are any other fresh water species 



