48 REPORT OF COMMISSIONER OF FISH AND FISHERIES. 



TRANSFER OF EGGS TO THE HATCHERY AND THEIR CARE. 



From Dead Brook the eggs are transferred to the hatchery at Craig 

 Brook station, about 2 miles, and spread on trays in the spawning- 

 house. The trays are placed in frames, inclosed in boxes which are 

 padded within to guard against concussion. In spite of all precautions 

 some of the eggs are occasionally killed, though the trays are placed in 

 pans of water and the eggs poured from the spawning-pans with the 

 greatest care. The frames or " stacks " containing the eggs are placed 

 at once in the troughs where they are to be developed. 



The trays are 12^ inches square, and constructed by attaching iron 

 wire-cloth to light wooden rims with blocks at the corners, so that when 

 piled up, one above another, there are narrow interstices on all four 

 sides, through which water circulates freely. The rims of the trays 

 are very slender, in order that they may never have buoyancy enough 

 to float, which woiild necessitate some means of holding them down and 

 increase the trouble attending their manipulation. Southern poplar 

 (whitewood) is commonly used, and a rim h inch wide and | inch deep 

 answers the purpose well, provided the wire be not very light. The 

 corner pieces are ^ inch thick, and give the interstices just enough 

 width to provide an ample circulation of water, but not enough to 

 allow the escape of salmon eggs, which are nearly ^ inch in diameter. 

 Eusting is prevented by varnishing the wire-cloth with several coats of 

 asphaltum varnish, which works better if made very thin by the use of 

 a large proportion of spirits of turpentine. The same varnish gives a 

 clean and glossy surface to submerged woodwork, and the varnishing 

 is extended to the rims of the trays, the ''stack-pans,"and the interior 

 surfaces of the troughs themselves. Material subject to rust should be 

 used only with great caution. Wire or other metallic forms galvanized 

 with zinc vary in quality. Total loss of eggs has been known to result 

 from the use of galvanized wire-cloth when unvarnished. Careful 

 experiment should precede the use of any particular brand. Tinned 

 wire cloth is better, but whether enough so to warrant the extra 

 expense is a question. 



In developing eggs, in order to economize room, the trays are piled 

 up 10 or 20 deep in frames that confine them only at the corners and do 

 not hinder the free passage of water horizontally through the "stack." 

 About 2,000 Atlantic salmon eggs are placed on a single tray, and a 

 trough of the ordinary length, lOi feet, therefore carries 140,000 to 

 280,000 eggs, with suitable free space at either end. It is therefore an 

 exceedingly compact apparatus and has the further advantage that it 

 can be used in a very plain trough which can, with a few minutes' work, 

 be transformed into a rearing-trough for young fish. For 10-tray stacks 

 the trough is made of pine boards. 12a inches wide and inches deep 

 inside, and is set up level, with the top about 30 inches from the floor of 

 the room. 



