194 FISH HATCHERY MANAGEMENT 



Figure 66. Commercially available shipping boxes can be used to transport fish 

 eggs. The boxes should be constructed to keep the eggs moist and cool without 

 actually carrying them in water, (l) A wet cloth is placed in the shipping tray 

 and the eggs are carefully poured into the tray. (2) The tray should not be filled 

 to the point where the next succeeding tray will compress the eggs and put pres- 

 sure on them. The cloth is then carefully folded over the eggs and the next tray 

 put in place. (3) The top tray is filled with coarsely crushed ice or ice cubes to 

 provide cooling during shipping. The melting ice also will provide water to keep 

 the eggs moist. Ice should never be used directly from the freezer and should be 

 allowed to warm until it starts to melt before it is placed with the eggs. (4) The 

 insulated lid is put in place, and the box is sealed and properly labeled for 

 shipping. (FWS photos.) 



and the fry have fallen through the mesh cloth, the trays are removed with 

 the dead eggs that remain on them. These units are relatively cheap and 

 easy to maintain, and egg picking is relatively simple. The disadvantages 

 are that rearing troughs must be available, there must be some means of 

 excluding light from the troughs while the eggs are being incubated, and 

 there is always a danger of improper water flow through the trays. 



CLARK-WILLIAMSON TROUGH 



The Clark- Williamson trough is a tray-hatching system for incubating 

 large numbers of eggs. The eggs are held on screen trays and are stacked 

 vertically rather than being placed horizontally in the trough. Dam boards 



