MANUAL OF FISH-CULTURE. 125 



4 feet wide, and 4 to 8 or more feet deep. They sLould be placed end 

 to end iu two rows, some 3 or 4 feet apart with a plauk walk between, 

 for convenience in caring for them. The hsh must be handled as little 

 and as gently as possible, otherwise the eggs will form into a hard mass 

 and never ripen. One cause of injury is the scoop net with which they 

 must be handled; the knots and the twine are so hard that they injure 

 the delicate scales of the whitefish, which struggles violently when 

 taken from the water. A net made by puncliing suitable-sized holes 

 in a sheet of thin, soft, flexible rubber would be yielding and perhaps 

 cause the least injury. 



HATCHING METHODS AND EQUIPMENT. 



At Put-in Bay the water for hatching is obtained from Lake Erie 

 through a pipe that extends 75 to 100 feet into the lake. Pumps 

 elevate the water to the loft of the hatchery, where it is received into 

 supply-tanks, whence it is distributed by the usual methods of piping. 

 The circular supply-tanks, two in number, are about 11 feet in mean 

 diameter, 8 feet high, and have a capacity»of 5,000 gallons each. These 

 tanks are necessary to give an equal i)ressure in the pipes and to 

 provide a supiily of water in the event of cessation of pumping. A 

 gauge in the boiler room shows the height of water in the tanks. 



Whitetish eggs are hatched in the McDonald jar and the Chase jar; 

 the former is in more general use iu the United States Fish Commission, 

 although both give satisfactory results. The eggs are put into the 

 hatching-jars by means of a dipper having a perforated bottom. The 

 proper number to a jar is 3f quarts, as determined by a gauge; these will 

 swell to4J[ quarts, which is about the proper quantity for the jars used. 



The form of the embryo whitefish can be seen iu the egg by the use 

 of a magnifying glass in from 10 to 15 days and the eye-specks and 

 color stars in from 15 to 20 days, the time depending much on the tem- 

 perature of the water. The fry being hatched, the food-sac is absorbed 

 in from 5 to 15 days, varying somewhat with the period of incubation. 

 If hatching is long retarded by low temperatures, the sac will be nearly 

 all absorbed when the fry hatches. 



The microscope is a great aid in whitefish culture, enabling the 

 operator to determine the exact percentage of dead eggs and to a great 

 extent the cause of their loss, thus allowing him to remedy some if not 

 all the evils. For examining eggs in their early stages the microscope 

 is placed horizontally, the eggs being held in a cell filled with water. 

 This may be easily made by fastening two ordinary glass slides to a 

 strip of wood an eighth of an inch thick, with a portion cut away to 

 form a receptacle for the eggs. The wood is thoroughly saturated with 

 asphaltum varnish, and after drying the sides should receive a thin 

 coat, the shdes being laid on and placed under pressure to dry. When 

 dry an additional coat to the outer joints of contact will guard against 

 possible leaks. 



