18 U. S. BUREAU OF FISHERIES. 



tion elsewhere is the comparatively small amount of milt produced 

 by the males. 



"When first taken the eggs are of a pale yellow hue and are almost 

 transparent, resembling a drop of honey. They are about one-sixth 

 inch in diameter, nonadhesive, and, because of the presence of a com- 

 paratively large oil globule, they are semibuoyant. The average egg 

 production is about 3,000 per pound weight of parent fish. The eye 

 spots, small gilt specks with a minute black pupil, appear in from 

 three to five days, and the eggs hatch in from 12 to 15 days in a water 

 temperature around 50° F. 



The eggs may be successfully incubated in the trays or baskets 

 ordinarily used in salmon and trout work, but, because of their 

 buoyant tendency, the Downing jar has been found more satisfactory 

 during the early stages of development. Approximately 125,000 eggs 

 are placed in a hatching jar and held to the eyed stage, at which 

 time it is customary to transfer them to trays for the completion of 

 incubation. 



A peculiarity in connection with the development of grayling eggs 

 is the appearance on the green eggs during the first day of an opaque 

 spot, which gradually enlarges until one-half the surface of the egg 

 is covered, giving it somewhat the appearance of a dead egg. This 

 cloudy condition is of short duration and by the end of the third or 

 fourth day is no longer visible. The embryo becomes active in the 

 egg before the eye spot can be seen by the unaided eye. 



Eyed grayling eggs can be transported without difficulty when 

 properly packed. Any of the methods in general use may be suc- 

 cessfully applied in the preparation of grayling eggs for shipment. 



FRY AND THEIR DISTRIBUTION. 



The percentage of fry produced from grayling eggs in Montana is 

 low, as a rule, seldom exceeding 50. The young fry are provided 

 with a very small yolk sac. On emerging from the egg they are 

 comparatively helpless and show little signs of animation until the 

 sac is practically absorbed at the end of the first week. They are 

 then free-swimming, about one-half inch long, and quite slender 

 and delicate, resembling the fry of whitefish or shad. At this period 

 they move about in search of food but are never as active as are 

 salmon or trout fry at a similar age. 



It is customary to distribute the fry within two or three days 

 after incubation is completed, since the attempts made to rear them 

 have not given good results. The fry do not take readily to arti- 

 ficial feeding, and when moved from hatching troughs to rearing ponds 

 they usually refuse food entirely for tlie first several days. How- 

 ever, the outcome of recent experiments along this line gives ground 

 for the belief that with proper facilities this difficulty in rearing 

 may be overcome. 



THE LAKE OR MACKINAW TROUT. 

 RANGE. 



The lake trout is found throughout the chain of the Great Lakes 

 and the inland lakes of northern New York, New Hampshire, and 



