OUR HERITAGE OF THE FRESH WATERS 
91 
GOVERNMENT MESSENGERS PLANTING FISH 
Before transferring fish from cans to an open stream, it is necessary gradually to bring the water in 
the cans to the approximate temperature of that in the stream; otherwise the fish will experience a shock. 
feet long when it died. Its length when 
received was about six inches. This spe¬ 
cies sometimes attains a weight of 8o 
pounds or more. It is likely that some 
species grow faster in freedom, where they 
find their natural foods, but other kinds 
may develop faster in suitable ponds, 
where they are well cared for and pro¬ 
tected from enemies. 
TELLING THE AGE OF A FISH BY ITS 
SCALES 
Wild fishes of exceptionally large size 
being often found, we may assume that 
fishes continue to grow through life, the 
period of life depending largely upon 
enemies. In a world beset with sharp 
fangs and claws, the life of a wild animal, 
either in the water or on land, is apt to 
end in a tragedy. 
It is now known that the scales of fishes 
bear marks which indicate the length of 
life and the rate of growth in different 
years. Studies of the Atlantic Salmon 
in Scotland and of the various species 
of Pacific Salmon have proved 
this. 
The scale grows in proportion with the 
rest of the fish, principally by additions 
around its border. The fish grows at dif¬ 
ferent rates during different seasons of 
the year. Concentric ridges form around 
the edge of the scale, its marginal ex¬ 
pansion in summer being more rapid than 
in winter, so that the growth during each 
year is usually distinguishable. (See il¬ 
lustration, page 8o.) 
Studies of the five species of Pacific 
Salmons have shown the ages at which the 
different species return to the rivers to 
spawn. Thus, the ridges on a fish’s 
scales are comparable to the annual ring 
