PROPAGATION AND DISTRIBUTION OF FOOD FISHES, 1922. 83 



aggi'egate number of fish eggs thus handled during the fiscal year 

 1922 was as follows : 



Chinook salmon 11,100 



Atlantic salmon 19,950 



Brook trout 49.870 



Rainbow trout 50,000 



Lake trout 1,000,000 



^VllitetLsh 600, 000 



Shad 1, 311, 000 



Total 3. 041, 920 



Fry to the number of 2,300,500 were hatched from these eggs, but 

 practically all of them were lost, as described above. 



An interesting occurrence in connection with the aquarium fishes 

 was the spawning of a pair of Potomac catfish. On the morning of 

 June 12 it was noted that a pair of Potomac catfish {Arnslwms 

 catus), which had been held in one of the small aquarimns since 

 April 29, had prepared a nest in the gravel covering the slate bottom 

 of the tank, and the female had deposited therein a glutinous mass 

 of eggs. The number was roughly estimated at 600, but this proved 

 to be considerably below the actual number. The male fish immedi- 

 ately assumed charge of the nest, working over it constantly, agi- 

 tating the water over the eggs with a quick gentle motion of the 

 pectoral, ventral, and caudal fins. He maintained his vigil from the 

 time the eggs were deposited until the fry were hatched and were 

 strong enough to leave the nest. At no time did he permit the female 

 to approach the nest. His labors were evidently for the purpose of 

 keeping the eggs free of sediment and circulating the water through 

 the mass. When first deposited, the eggs were of a pale-blue color. 

 The incubation period was eight days in a mean water temperature 

 of 75° F. 



When the fry first emerged from the egg, they were about one- 

 fourth inch in length, transparent, and of about the same color as 

 the egg. They remained on the nest for the first six days, at the end 

 of which time they began rising a few inches above it, at first falling 

 back almost immediately, but gradiuilly remaining longer above the 

 bottom. By the eighth day they were strong swimmers and seemed 

 about to scatter. On the ninth day they were transferred from the 

 aquarium to a hatching trough, numbering at that time 1,453 by 

 actual count. In the trough they received food (beef heart) twice 

 a day, which they took readily. They made excellent growth. 

 When nine days old, they averaged five-eighths of an inch in length 

 and by the end of June, when 19 days old, 1 inch. 



Part 2— DISTRIBUTION OF FISH AND FISH EGGS. 



[E. C. Pearnow, Superintendent of Fish Distribution.] 



The total net output of the bureau's stations (see table, p, 8) for 

 the fiscal year 1922 (5,125,101,320 fish and fish eggs) was widely dis- 

 tributed, shipments of fish and eggs being made throughout the States 

 and to Alaska and Hawaii and assignments of eggs to Canada, 

 Czechoslovakia, and Switzerland. About 99 per cent of the output 

 was made up of fish and fish eggs of commercial species, which were 

 planted in waters where the egg collections were made, except in 



