ARTIFICIAL PROPAGATION OF WHITEFISH, ETC. 7 



water-tight. The tray is placed in the tray board, which has pre- 

 viously been filled with water. The eggs are poured on the partly sub- 

 merged tray and at once spread evenly over its surface. For longer 

 distances greater j)recautions must be taken and a packing case that 

 has space for proper insulation and ice used. Several modifica- 

 tions of this t3-pe of case are in general use in fish-cultural work. 



After the eggs are placed on trays and drained they are covered 

 with a thickness of mosquito netting that has been well washed and 

 left damp. If the eggs are to go by express, unaccompanied by a 

 messenger, directions stating that they must be kept cool but not 

 permitted to freeze are fastened to the case. Whitefish eggs, ac- 

 companied by an attendant, have been safely shipped from North- 

 ville, Mich., to Australia. Where eggs are to be shipped from one 

 station to another, in care of a messenger, the regular field cases are 

 used. 



The trays used at the station are 18 inches square and are made 

 of white pine f by 1 inch, mortised together at the corners, with the 

 widest side of the strip horizontal. Cheesecloth or linen scrim is 

 tacked on the bottoms of these frames with galvanized or copper- 

 coated tacks, the cloth being stretched very taut to prevent its 

 sagging after being wet and dried. The tacks are spaced 2| to 3 

 inches apart, so that in a year or two the cloth may be retacked be- 

 tween the spaces to take up the slack. As the trays are square, they 

 fit into the cases either way, thus saving time in packing. Square 

 cases are also more convenient to store and for general handling. 

 One of these trays will hold 100,000 whitefish eggs. 



Where the eggs have to be retained in the field for several days 

 they are sometimes kept in floating boxes adapted for the purpose, 

 but unless the conditions are very favorable it is far better to place 

 them on trays, sprinkling them lightly once in two or three days. 

 (See description of floating box on p. 23.) 



When taken from the. kegs and trays at the hatchery, the eggs 

 are passed through a screen with meshes sufficiently large to permit 

 the passage of a single egg in order to remove scales and other 

 foreign substances that may be present. The screen is floated in a 

 washtub partly filled with water, with the wire netting well sub- 

 merged. 



Wooden kegs are preferred to tin cans for handling eggs and fry, 

 as their contents are not subjected to sudden changes in tempera- 

 ture and can be readily examined, and as the water can be more 

 easily poured off without risking the loss of eggs. Kegs are also 

 much lighter, cost only a sixth as much as cans, and last longer. 

 For shipment in wagons or by rail, however, tin cans made with 

 covers are indispensable. The kegs should be of white pine, made 

 large enough to hold about 15 gallons, and painted on the outside 

 but not inside. They should be provided with iron drop handles. 



PENNING WILD FISH. 



The uncertainty of climatic conditions and the liability of fail- 

 ure to obtain spawning fish during the severe storms occurring in 

 November make it desirable, whenever practicable, to capture fish 

 when the weather is favorable and place them in pens to ripen. 

 If the fish are driven off their spawning grounds by heavy storms, 

 52881'— 2.3 2 



