NATURAL HISTORY OF BRITISH SALMONID^. 135 



by ascending thus early, before their spawn is at all matured, 

 are vigorous, and able to overcome the obstacles in their upward 

 course to the extreme sources of the river — to which those fish 

 remaining in the sea until heavy with spawn could never pene- 

 trate. 



Curiously enough, an analogous fact has been noticed with 

 regard to the spawning of the common trout. Dr. Davy, who 

 was in the habit of opening the fish he caught, records that by 

 this means he discovered that, as the spawning season ap- 

 proached, only about one-half of the females had visible eggs, 

 whilst in the other half there were no signs of the development oj 

 the ova. Charr, also, are frequently taken in Windermere in 

 high condition in October and November, which is their regular 

 spawning season — a fact which would seem to point to the pos- 

 sibility of the rule of alternate spawning years holding good in 

 the case of all the fish of the salmon and trout species. 



But to return. The ascent of salmon to the spawning 

 grounds is usually somewhat in this wise. During the early part 

 of the season, the fish in the rivers, which do not at once 

 ascend, remain in or near the mouths. But with the advance 

 of the season they get gradually farther into the fresh water 

 beyond the influence of the sea. The edible quality of the 

 salmon when thus ascending rivers depends entirely upon the 

 state of development of the milt or roe— a loss of condition, 

 accompanied by the usual change of colour, following, even in 

 the salt water, upon the maturing of the spawn. The efforts of 

 the salmon to surmount all obstacles to their ascent of the 

 rivers increase with the approach of the spawning time, and 

 they shoot up rapids, and make wonderful exertions to surmount 

 cascades and other impediments, frequently clearing a height 

 of two or three yards at a bound. It has been calculated that, 

 when swimming, or rather darting at full speed, the salmon will 

 glide through the water at the rate of about 1,500 ft. per minute, 

 or upwards of 400 miles per day — a pace which, if it could 

 be maintained, would speedily carry the fish round the world. 



Although the height to which a salmon will leap seems 



