ABTIFICIAL. PROPAGATION OF TEOUT. 43 



When injured in this way, the ovary may not recover its natural 

 function and may become sterile. If, however, simple precautions 

 are observed, no injury to the fish will result. As an illustration it 

 may be mentioned that fish have been kept for 14 years and their 

 full quota of eggs extracted each season during the egg-producing 

 term, which is normally from 10 to 12 years. The male fish is to be 

 treated very much in the same manner as the female, except that the 

 milt must not be forced out, as only that which flows freely is of 

 value. 



After stripping, the fish are not returned to the spawning pond, 

 but spent females are placed in one pond and males in another. The 

 males are very pugnacious at this season and sometimes fight for an 

 hour or more at a time until they are entirely exhausted; they run 

 at each other with open mouths, lock their jaws together, and in that 

 position sink to the bottom of the pond, where they lie for a short 

 time, each holding the other in his grasp until rested, when they rise 

 and resume the combat. As their teeth are abnormally long, they 

 scar each other and even bite pieces of skin and flesh from the sides of 

 their antagonists. 



From 15 to 25 per cent of the females yield eggs the second year, 

 about 60 per cent the third year, and from 80 to 90 per cent each 

 season thereafter. From 10 to 15 per cent of the fully matured 

 females are barren each season. At one time it was thought that the 

 same individuals were barren each year, but experience has shown 

 that such is not the case, as fish that were barren one season have been 

 held over in a separate pond until the following year when a large 

 proportion, if not all, produced eggs. The sterility may be the result 

 of injuries received during the progress of spawning. The males are 

 good breeders when 2 years old. 



PRODUCTION or EGGS. 



The number of eggs produced by a fish depends upon its size and 

 age. The maximum from one 2-year-old fish, weighing from 6 to 12 

 ounces, is from 500 to 800 ; from one 6-year-old, weighing from 2 to 4 

 pounds, it is 2,500 to 3,000. The average of fish from 3 to 6 years old 

 is 1,200 to 1,500. The eggs vary in size from 4| to 5 eggs to the linear 

 inch, and from 300 to 360 per fluid ounce, according to the age of the 

 fish, though in some localities larger eggs, averaging not more than 

 220 to 240 per fluid ounce, are not uncommon. They are of a rich 

 cream color when first taken, changing to a pink or flesh tint before 

 hatching. Eggs from wild fish are of a pink or salmon color, and 

 as a rule average somewhat smaller than those from domesticated 

 fish. 



HATCHING TROUGHS AND TRAYS. 



The eggs are incubated on trays placed in troughs of wood, metal, or 

 concrete and of various shapes and sizes. Standard troughs are 14 feet 

 long, 14 inches wide, and 8| inches deep, inside measure. They are set 

 in pairs, as shown in Figure 13, page 44. Six inches from the lower 

 or outlet end inside is a guard screen of perforated zinc or wire mesh, 

 fastened on a frame exactly fitted across the trough. Zinc with per- 

 forations one-sixteenth of an inch in diameter for very young fry, 

 and larger ones as the fish increase in size, is preferable to wire cloth. 



