BROOK TROUT. 
85 
sion in 1900. The usual age of maturity under natural conditions is doubtless somewhat more 
advanced. As shown in another place, the size of the fish does not indicate its age, therefore 
breeding brook residents only two or three inches long, are not necessarily young fish although 
possessing parr marks. 
According to Livingston Stone, all two-year-old trout spawn; some yearlings do and some 
do not; and the main dependence of the trout breeder for eggs is on trout upwards of two years 
old. 
The duration of fertility is also variable, but has not been ascertained. But very large 
fish, although present on the spawning grounds, are often found to be old and practically sterile. 
The eggs vary in size, but are usually one-sixth of an inch in diameter. The number 
yielded by one fish depends on its size and age, yearlings usually producing from 150 to 250, 
two-year-old, 350 to 500, and older fish, 500 to 2,500 (Manual of Fish Culture). 
Livingston Stone states: “The number of eggs to a fish is given as one thousand to the 
Text-fig. A. — Head of male Brook Trout. 
Text-fig. B. — Head of female Brook Trout. 
pound, but it is often more than this, and varies much with the size of the eggs, those having 
small eggs yielding the most in number. I have taken eighteen hundred eggs from a pound 
trout, and once took over sixty eggs from a trout that weighed just half an ounce immediately 
after being stripped.” 
Regarding the size of the eggs Stone says: “The eggs of the trout are large compared with 
those of most fish, except the salmon. They average about three sixteenths of an inch in diam- 
eter, varying very considerably in size, the very largest containing probably twice the bulk of 
the very smallest. 
“They are sometimes colorless, sometimes orange-hued, and sometimes have a rich red 
tint. The cause of the variation in the color of the eggs is not positively known. It has been 
