SALMON AND TROUT CULTURE. 467 
of Salmonidz, 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 Salmonide, 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 ih appear- 
ance as Fario, Levenensis, and Ferox, when small, to guarantee 
that they are not mixed ; 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. Ihave found small perch in one set of 
mny nursery ponds, which mus¢ 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 
HH2 
