PISCES 121 



While in the hatching trays the eggs are examined frequently, and 

 are sometimes stirred and rolled over with feathers; sometimes they are 

 stirred by raising and lowering the trays in the water; and any eggs that 

 escaped fertilization, or for any other reason have died, are carefully 

 removed before they have time to mold or decay and infect the good 

 eggs. A dead egg has a sort of opaque appearance that, with a little 

 experience, is easily recognized. The hatching trays are of various 

 types, a common form being a box about 15 X 24 inches and 6 inches 

 deep made of galvanized wire netting. These trays, containing 

 thousands of eggs, are usually placed in narrow, wooden troughs with a 

 series of transverse partitions so arranged that the stream of water that 

 passes through them is forced upward through the eggs in the tray 

 and keeps them thoroughly mixed and aerated. The arrangement of 

 trays, etc., varies at different hatcheries and with varying conditions. 



In a month or more, varying with the temperature of the water and 

 other conditions the eggs hatch and the young fish, with the huge yolk 

 sack attached, wriggle out of the trays and are taken care of until the 

 yolk is absorbed and the fish are active and able to take care of them- 

 selves if liberated into the waters of a suitable stream. While the yolk is 

 still present the fish will not feed, but if they are kept longer they must 

 be fed at frequent intervals on finely minced liver or other meat, great 

 care being taken to prevent fouling of the water by uneaten scraps of 

 meat. 



One of the primary factors in handling the eggs and young fish is 

 cleanliness. Unless the water is of exceptional purity it must be led 

 into settling tanks where the heavier sediment settles to the bottom 

 and then it may be necessary to strain it through cloth to remove the 

 finest particles of foreign matter that in the open streams, settles over 

 the eggs and causes high mortality. Another factor is a free circulation 

 of water in sufficient quantity to keep the eggs in motion and to keep 

 them well aerated. It is often important that the temperature of the 

 water be low during the season when hatching is in progress. 



When the young fish or "fry" have reached a proper size it is often 

 necessary to transport them long distances to the place where they are to 

 be liberated. For this purpose, as noted above, the Bureau of Fisheries 

 employs several cars with tanks and aerating devices. The vessels 

 most commonly used for handling the fry are the ordinary, large 

 milk cans, holding about 15 gallons. The water in these cans must 



