THE SALMON. 285 



fry in small artificial ponds, and observing their growth, 

 is led to surmise that none of the salmon fry leave the 

 river in which they are hatched until they have acquir- 

 ed the age of two years, and during the whole of that pe- 

 riod he believes their growth to be not more than six inches 

 in length, or three inches for the first twelve months.* Un- 

 der this head, I may here remark that allanimals while placed 

 under confinement, and deprived of their natural food, are 

 found to make but little progress in their growth ; in proof 

 of which, it is recorded in the second volume of Mr Yar- 

 relPs British Fishes, that a trout about a pound weight had 

 lived for twenty-eight years in a well at Dumbarton Castle, 

 and had never increased in size from the time of its being 

 put in. The kind of food exerts a material influence on 

 the growth of fishes, as mentioned by Mr Stodart in his in- 

 teresting work on the Art of Angling. " Trout were placed 

 in three separate tanks, one of which was supplied daily 

 with worms, another with live minnows, and the third with 

 those small dark coloured water-flies which are to be found 

 moving about on the surface under banks and sheltered 

 places. The trout fed with worms grew slowly, and had a 

 lean appearance ; those nourished on minnows, which, it 

 was observed, they darted at with great voracity, became 

 much larger; while such as were fattened upon flies only, 

 attained in a short time prodigious dimensions, weighing 

 twice as much as both the others together, although the 

 quantity of food swallowed was in nowise so great." The 

 natural and most nutritious food of the salmon fry during 

 the months of March, April, and May, is, there is no doubt, 

 flies and the larva of insects, which, in small and recent ar- 

 tificial ponds, are comparatively scarce. 



Edin. Phil. Jour, for 1836 and 1838. 



