28 U. S. BtTREAU OF FISHERIES. 



in small spring- fed tributaries when possible. Wliere deliveries of 

 fish are to be made to individuals or organizations on formal appli- 

 cation, the applicant is expected to meet the shipment at the rail- 

 road station and effect the necessary arrangements for their final 

 planting. The demand for fingerling'fish for stocking streams far 

 exceeds the available supply. 



The methods outlined on page 47 for handling fry may be ap- 

 plied advantageously to brook trout, and where it is necessary to 

 economize, either in space or in the flow of water, the fry may be 

 carried through the sac stage on trays stacked one above another in 

 the trough compartments as is done with the eggs. In employing 

 this method it is customary to transfer the eggs from the hatching 

 trays to trays similar in size but covered with wire cloth 16 meshes 

 to the inch just prior to the time of hatching. The more open mesh 

 is desirable during the incubation period, as it gives a freer cir- 

 culation of water, but the smaller mesh must be used to hold the 

 fry successfully. This method of carrying fry is practiced exten- 

 sively in fish-cultural operations addressed to such important com- 

 mercial species as the Pacific-coast salmons and the lake trout of the 

 Great Lakes. 



REARING AND FEEDING. 



If the fry are to be reared for breeding, one week before the food 

 sac is absorbed they should be changed from the trays to a large pan 

 and removed to the rearing troughs. Gravel may be used in 

 these troughs, but in general practice it is undesirable, as the uncon- 

 sumed food works down into it and, becoming fungussed there, causes 

 a great spread of disease and increases the labor of caring for the 

 fish. 



Trout fry are ready to be fed regularly when they rise to minute 

 particles of food thrown upon the water. The time and frequency of 

 feeding young fish, the kind of food, and the manner of feeding them 

 are of the utmost importance. A difference of opinion exists among 

 fish-culturists as to how often young trout should be fed, but the 

 majority is in favor of feeding them from five to six times a day 

 until they are a few weeks old and after that giving them larger 

 quantities of food at less frequent intervals. Only such an amount as 

 the fish will eat readily at one time should be spread upon the surface 

 of the water with a feather until they are accustomed to taking it. 



While various foods have been fed more or less successfully, it is 

 believed that beef heart and beef liver give better results than any 

 artificial food, and their preparation is very simple. A less expensive 

 and very satisfactory substitute is beef melts or spleen. The meat 

 is first ground fine by running it through a meat chopper several 

 times, using a plate with perforations five sixty-fourths of an inch 

 in diameter, a little water is added, and the meat beaten to give it 

 the proper consistency. An egg beater is used by some fish-cultur- 

 ists in preparing the food. The finely ground meat is placed in a 

 deep pan, with sufficient water to bring it to the proper consistency, 

 and then thoroughly mixed with the egg beater. This removes 

 practically all the small particles of connective tissue and muscle 

 which orclinarly pass through the finest plate of the meat chopper 

 and cause trouble by clogging the screens and fouling the troughs. 



