SPAWNING GROUNDS. 49 



whilst in others, very similar, the fish are often 9 Ibs. 

 each; in this latter case we may suppose the ocean 

 and the river afford them a supply of better food in 

 greater abundance. 



We may assume that the food in the ocean may 

 be greater in some or less in other seas. The food in 

 the rivers varies. Some rivers drain a peaty, poor 

 soil, in which the fish from its infancy is stinted, and 

 consequently its growth is checked. Other rivers 

 drain rich soils, abounding in insect life ; hence in 

 these the fish from their infancy are abundantly sup- 

 plied with food, and the smolts are larger when they 

 migrate to the sea than those born in rivers which 

 drain a poor soil, just as a mountain sheep is smaller 

 than another reared upon a rich lowland pasture.* 



As to the quality of the water, this, I have no doubt, 

 varies in different rivers, from the nature of the soil 

 and bed of the river over which the waters flow into 

 the sea ; as the some fish return from the sea to the 

 river of which they are natives. It is also known that 

 salmon traverse along the shores of the sea beyond 

 their own river's mouth, for distances of 40 or 50 

 miles, and pass and repass the mouths of other rivers, 

 and yet return to their own native river to breed ; for 

 example, there are three or four salmon rivers flow 

 into the Frith of Moray, in Scotland, in one bay ; 

 they all associate and live together for some months 

 in the sea, until the period arrives for their return, 

 when each class of fish returns to its own river, as 

 they are well known to the fishermen who catch 

 them, from there being distinguishing features in the 

 shape of each class of fish known to inhabit these dif- 



* The late Duke of Atholl, in March, 1859, caught three salmon, 

 on their way to the sea, weighing 10, llf, and 12$ Ibs. each ; these 

 same fish having been marked by the Duke by a copper band round 

 their tails, returned in six months, and were again captured, having 

 increased to 17, 18, and 19 Ibs. each. They went to the sea as lean 

 kelts, and had become fat from the quantity of food they had found. 



