72 



U. S. BtTREAIT OF FISHERIES. 



In addition to the hatchery exhibit a display of adult fresh-water 

 fishes was maintained in the aquaria throughout the year. The 

 total number of fish exhibited was 2,614, representing 45 species. 

 Collections for restocking were made from time to time from the 

 Potomac River at Bryans Point, Md. Other sources of supply were 

 the bureau's stations at White Sulphur Springs, W. Va. ; Bellevue, 

 Iowa; Bozeman, Mont.; the New York Aquarium, and the New 

 York Conservation Commission hatchery at Caledonia, N. Y. 



The health of the aquaria fishes throughout the j^ear was gener- 

 ally good, with the exception of a short period during May and 

 June, when a number of the fish were attacked by the parasite 

 Ichthyophthirius, causing a considerable loss, particularly among 

 the warm-water fishes. It has recently been found that this para- 

 site may be destroyed by .treating the fishes infected with a saturated 

 solution of bicarbonate of soda. The solution is conveniently ap- 

 plied directly to the fish when held in shallow water with a small 

 paintbrush. The treatment removes the mucous coating from the 

 fish and destroys the parasite with no injuiy to the fish. 



Spawning Seasons of Fishes Handled at Stations. 



Records of the spawning seasons of the various species of fishes 

 handled at the bureau's stations during the fiscal year 1921, together 

 with the water temperatures at the beginning and end of such pe- 

 riods, are given in the following table, in which the stations are 

 grouped and arranged as in the preceding discussion of the propa- 

 gations of the conmiercial species and the species for stocking the 

 interior waters; that is. Pacific salmon. Great Lakes, Marine, New 

 P^ngland salmon and trout. Rocky Mountain trout, combination 

 trout and pond fish-cultural, and pond fish-cultural stations. 



Spawning Skasons of Fishes Handled at Stations, with Water Tempera- 

 tures AT Beginning and End of Periods, Fiscal Year 1921. 



PACIFIC SALMON STATIONS. 



