On Stocking. 49 



growing, when they have reached a certain limit. Range also 

 influences the rate of growth. Large ponds grow trout faster 

 as a rule than small ponds. Put ten trout in a pool three 

 feet square, and ten others in a pond ten rods square, and 

 those in the pond will grow much faster than those in the 

 pool on the same food.' 



Stone of course writes on the American brook 

 trout, S. fontinalis, which is a first cousin of the 

 Highland Chars ; but the above extract is equally 

 applicable to our British trout. Stone goes 

 on to impress the necessity of giving trout plenty 

 of space, and dilates on the difference between 

 range and space ; but in this matter I do not 

 entirely hold with him. Space means the cubic 

 feet of measurement in each pond divided by the 

 number of trout. Now, the real factor is com- 

 posed of surface measurement ; gallons of fresh 

 water or cubic feet of fresh water supplied per 

 minute ; and cubic contents of the pond in feet ; 

 and it is further varied by the capacity for 

 oxygen of the water a capacity which is exceed- 

 ingly variable. 



The real crux is to furnish each fish with a 

 sufficient supply of oxygen. The water may be 

 considered as the medium from which this supply 

 is obtained. Again, the quantity of available 

 oxygen must be proportioned to the gross weight 

 of trout, and not to the number of fish, and again, 

 a slight rise of temperature will double or treble 

 the quantity of available oxygen required. I 



