8 U. S. BUREAU OF FISHERIES. 



they do not return in large numbers during the spawning season, 

 and the only way to insure a satisfactory supply of eggs is to pen the 

 fish. Penning has been abandoned in most of the Great Lakes 

 fields, because most of the fish are taken by gill nets. Since pound 

 nets are seldom used, the green fish can not be obtained. Most of 

 the fishing boats take their own eggs and deliver them to the 

 bureau's agent in charge of the field. 



The pens are usually made about 16 feet long, 8 feet wide, and 5 

 feet deep and are placed end to end in two rows, with a plank walk 

 between as a convenience in caring for them. A partition is placed 

 in the center of each pen, dividing it into two compartments, each 8 

 feet square. In each compartment is a false bottom held down by 

 two 2 by 4 pieces fastened to the sides. Wlien the fish are to be re- 

 moved the false bottom is raised and held at any desired height by 

 inserting pins in the 2 by 4 pieces and the sides of the pens. The 

 fish 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 twine being so hard that they injure the delicate scales of the 

 whitefish in their violent struggles when taken from the water. 



Although crates or inclosures of wood construction have been very 

 generally used by the Bureau of Fisheries for penning whitefish, 

 retaining inclosures of cotton webbing are proving very satisfactory 

 in Lake Ontario. 



HATCHING METHODS AND EQUIPMENT. 



The water supply in the hatchery at Put in Bay is obtained 

 through a pipe extending 75 to 100 feet into Lake Erie, the water 

 being elevated by pumps to supply tanks in the loft of the hatchery, 

 whence it is distributed by the usual methods of piping. Two circu- 

 lar galvanized-iron supply tanks ^re used, each having a capacity of 

 approximately 18,000 gallons. These tanks are necessary in order 

 to give equal pressure in the pipes and to provide an even supply 

 of water to the whitefish batteries. In the event of being obliged to 

 suspend pumping operations for a short time, there will be sufficient 

 water in the supply tanks to care for the eggs for a period of several 

 hours. A float connected with the throttle valve of the pumps is so 

 arranged in the tanks as to maintain a steady water level therein. 



Whitefish eggs are hatched in the open-top McDonald, Downing, 

 and Chase jars, the Downing and Chase jars being more generally 

 used. On arrival at the hatchery the eggs are taken from the 

 shipping-box trays and placed in tubs of water to harden. After 

 remaining in the tubs from 12 to 14 hours, during which time the 

 water is changed once an hour, the tub of eggs is placed on a mov- 

 able stand and the eggs measured intO' jars by means of a dipper. 

 The jar is first filled with water and a shallow funnel with an out- 

 let extending well into the jar inserted, so that the water will 

 stand as high in the funnel throat as possible. In this way the 

 eggs are not subjected to a fall from the dipper to the jar. 



From this stand the jars are passed to a man who sets them up on 

 the batteiy. Tin tubes are placed in the jars and connected with 

 faucets supplying the water by rubber tubes. In the battery de- 

 scribed each jar on the top row is provided with a water supply of 



