SALMON AND TROUT CULTURE. 467 



of Salmonidae, over forty ponds, about thirty of which are 

 usually set apart for rearing yearling fish and for food-growing. 



A number of ponds is necessary, as there are at least five 

 favourite varieties of Salmonidae, viz. Salmo Fario (English 

 brook trout), S. Fontinalis (American do.), S. Levenensis 

 (Loch Leven do.), S. Ferox (Great Lake do.), and Thymallus 

 Vulgaris (Grayling) ; and there would be immense trouble in 

 separating them if the different varieties were placed in the 

 same pond. Fontinalis and grayling could be readily distin- 

 guished, but it is no slight work with fish so similar in appear- 

 ance as Fario, Levenensis, and Ferox, when small, to guarantee 

 that they are not mixed j it would be more simple if the fish 

 were not so active, and the water not quite so chilly. 



The ponds for the large breeding fish are constructed on a 

 different * water-shed,' or at all events on different levels from 

 the rearing-ponds, and are so fenced that there is no possibility 

 of the larger fish getting into the nurseries, or the small fish 

 getting out. The area of the ponds for the breeding fish is 

 much larger, and the water deeper. Ponds for sport only 

 may be as large as possible, and the bigger the better, but in 

 all cases they should be capable of being emptied, as there 

 is sometimes the probability of pike or perch getting in, and 

 these might have a real good time of it amongst the trout, 

 before detection. A few very large trout will also do as much 

 damage, amongst smaller fish, as pike, and if the water can 

 be run off they should be removed or destroyed. Pike and 

 perch are occasionally introduced into trout waters through the 

 medium of water-fowl. I have found small perch in one set of 

 my nursery ponds, which must have been conveyed by birds, 

 in the ova stage, as there were no perch nearer than five miles, 

 and these were in ponds on another water-shed. 



The presence of pike in some of our best trout waters is 

 the curse of the place, and it seems to be impossible to get rid 

 of them, although a price is set on their heads. One reads of 

 hundreds of pike having been killed during the season from 

 some favourite trout- stream ; but it seems probable that the 



