152 SALMON-REARING AT STORMONTFIELD. 



salmon, is decidedly superior. Why? How is it that 

 this little stream has not its equal in all England for 

 the size and flavour of its trout? Mr Francis surmises 

 that the fresh-water pulex or screw has not a little to 

 do with the production of this marked superiority. " I 

 have seen the trout picking them at the walls, which 

 pen the stream in some places, as rapidly as a child 

 would pick blackberries from a hedge ; and I am in- 

 duced to think that this insect has much to do with 

 the fineness of the fish ; and the more so because, 

 when I have found it to exist in any quantity, I have 

 invariably observed that the trout are of fine size, and 

 in unusually good condition." 



Hence the feasible suggestion that the entomologist 

 and the botanist shall assist pisciculture by ascertain- 

 ing the kinds of living creatures and plants on which 

 fish thrive most, and by pointing out how they may 

 be introduced into localities where naturally they do 

 not abound. 



The bottom of Loch Leven is in some places covered 

 with a peculiar weed, sheltering various insects, chiefly 

 crustacese, and small snails of various sorts ; the lake 

 also abounds in the more minute entomostracas. Large 

 quantities of both are found in the stomachs of the 

 trout. And therefore, when recently consulted as to 

 stocking a certain water with this prized trout, we in- 

 sisted on the ova being accompanied by a quantity of 

 the weeds and small stones to which the favourite food 

 of the fish would adhere. 



Besides noting what fish eat, Mr Francis would have 

 pisciculturists note the creatures that eat fish or their 

 spawn. He is particularly wrathful with Thames swans, 

 whose voracity for fish spawn he has often witnessed. 

 Allowing a swan the moderate daily allowance of a 

 quart of trout spawn (containing at least 50,000 eggs), 

 and supposing that only 200 swans are at work (about 

 a fourth perhaps of the number really employed), he 

 makes out that in a fortnight they will have devoured 



