ALASKA SALMON INVESTIGATIONS IN 1900. 
307 
Period of incubation . — The temperature records are not at all complete, and no 
attempt has been made to determine the thermal hatching unit. Generally it may 
be said that with a temperature of 45° F., the average highest, to 39°, the average 
lowest, the eye-spots appear in from 30 to 38 days. A few are earlier, and a few are 
45 days before they are well eyed out. In 90 days they are hatching rapidly; in 100 
days two-thirds are hatched; in 110 days four-fifths are out, and the remainder 
straggle along for several months. As the hatchery closes March 1 the unhatched 
eggs are buried in the gravel, simulating the natural conditions. The cohoes hatch 
about 10 days earlier, and an experiment made with a basket of humpback eggs 
showed that they hatched in 70 days under conditions in which the redhsh hatched 
in 90 days. 
Eggs which hatch out well in advance of the mass (“prematures”) and those 
equally late, produce usually very weak fish or “freaks.” It has been the experience 
here that it is useless to waste time on these fish, as they invariably die. It has been 
found that the fry just hatched collect in the lower end of the troughs, and to prevent 
loss they are removed as early as possible, within a day or two after hatching, and 
placed in the nursery, the upper ponds of the feeders, and sometimes in the lake, 
where the bottom is grassy or covered with pond lilies. 
The yolk-sac is absorbed in from forty-five to fifty days, but shows plainly at 
sixty days, though skinned over and in the belly. After this has taken place they 
are taken from the nursery and some are placed in the feeders and others in the lake, 
where the natural conditions are most favorable for their protection. 
The loss varies from 8 to 12 per cent, depending upon the season; if t here is an 
abundance of rain, permitting the fish to ascend without injury, the eggs are found 
in good condition and the loss is small. During a dry season the fish are kept from 
ascending until the fall rains, and as they partially ripen in the salt or brackish water 
the eggs are more easily injured. Realizing the advantage in having the fish arrive 
in the lake in a healthy, vigorous state, considerable work has been done at the out- 
let to remove obstructions and to improve the natural conditions. 
Barren lakes. — Mr. Callbreath lays considerable stress upon the use of what he 
terms barren lakes in connection with hatchery work. These lakes have in their sea 
connections high falls or cascades preventing the passage of fish from the sea and 
usually are quite clear of the enemies of salmon fry. Mr. Callbreath has planted 
redfish fry in two of these barren lakes, both discharging their water into Burnett 
Inlet. In 1894 and 1896, 1,000,000 redfish fry were planted each year in Burnett 
Lake, about 13 miles from the hatchery, and in 1895, 2,000,000 redfish fry were 
planted in Francis Lake, about 11 miles from the hatchery. The following coho fry 
have been planted in Falls Creek, previously referred to: 1893, 66,000; 1894, 50,000; 
1896, 135,000; 1899, 60,000. The rest of the hatchery output has been planted in 
the home lake and feeders. The fry are transported as soon after hatching as the 
weather permits and before the egg sac is absorbed, as they then require fewer 
changes of water. Coal-oil cans are used for transportation cans; a screw-top 
mouthpiece, 11-inch opening, is soldered to the top of the can and the fry are 
poured in through a funnel having a large opening. A 5-gallon can will hold 30,000 
redfish fry, or about 15,000 coho fry, and two such cans placed in the original case 
make a load for one man carried on the back with pack straps and, if the weather 
is cold, wrapped in blankets. 
