DO GRAYLING INJURE TROUT STREAMS? 301 



and for this reason alone grayling will increase faster than 

 trout, as this source of destruction (a very large one in 

 mere trout streams) is wanting as regards the grayling ; 

 and added to this, as the ova are much smaller, and they 

 are far more numerous than those of the trout. Grayling 

 certainly are more of burrowers and ground feeders than 

 trout ; and if it be thought that the grayling do really 

 diminish the trout, a little artificial breeding would easily 

 keep up the balance. But I conceive that when grayling 

 are introduced into fairly stocked pure trout streams, the 

 following change takes place : as the grayling increase, the 

 trout must either fall off in condition or diminish in num- 

 ber somehow, for a stream will only support a certain num- 

 ber of fish up to a certain size and condition ; and if, for 

 example, it holds 5,000 trout you cannot put 5,000 gray- 

 ling into it as well, and still keep up the number and con- 

 dition of your trout. But if, for the sake of extending 

 your sport for many months, or for the variety, you are 

 satisfied with a slight diminution in the weight of your 

 baskets of trout, then you can do well enough ; or, if this 

 does not suit, then you must resort to a large system of 

 artificial feeding. To what extent we can or could carry 

 this point of the question in an open stream, is a calcula- 

 tion which experiments in fish culture, to be carried out 

 in the future, alone can assure us of. Everybody can under- 

 stand that if a field of turnips will support fifty sheep for 

 a month, and you turn twenty cows into it as well, the 

 field will not support the additional call made on it for the 

 same period ; but if you choose on this space to draw cart- 

 loads of turnips, then you can support any reasonable 

 quantity of stock as long as you like, and even fatten them 

 like pigs or prize cattle, the increase being regulated by 

 the quantity of turnips you draw on. A stream is in this 

 sense a field of turnips, and you must till it and stock it 

 accordingly ; but you must not be surprised, if you starve 



