PROPAGATION AND DISTRIBUTION OF FOOD FISHES, 1923. 81 



quality, and it is believed it will do much toward the eradication, 

 of thyroid tumor, which appears to have gained a foothold among 

 the brood stock. The presence of this disease is believed to be due 

 in large measure also to the method employed in cleaning the ponds. 

 Under certain conditions it is necessary to wash all accumulations 

 of sediment down through a pond containing fish to the outlet at a 

 time when the depth of the water does not exceed 8 to 10 inches. 

 This is not considered conducive to the health of the fish, since a 

 large amount of the waste matter must pass through their gills. 



With the view of improving the methods in this respect a bulk- 

 head extending about 6 inches below the surface of the water was 

 recently installed about 12 feet below the upper end of one of the 

 l^onds, with a gateway in the center of it. When cleaning this 

 Ijond the water in the upper section is lowered and that portion 

 cleaned first, after which a seine is passed around the fish, causing 

 theui to enter the cleaned portion; the gate is then lowered, and 

 the remainder of the pond cleaned without subjecting the fish to 

 insanitary conditions. 



Acting on a suggestion from the fish pathologist, a small quantity 

 of iodine solution was mixed with the food given to one lot of fish 

 in the hope that it might tend to lessen, if not prevent, the develop- 

 ment of thyroid tumor. Sufficient time has not 3'e't elapsed to permit 

 of any statement as to its eftect upon the fish. 



The pathologist discovered that a large number of ailing No. 1^ 

 fingerling trout were infested with flagellate. It has been noted that 

 the mortality among fingerling trout of this size is considerably 

 greater than among older fish, and also that it is heavier in the 

 spring than at any other season of the year. 



The filtering system was used during the incubation period and 

 up to the time the fingerling fish were distributed. By the use of 

 a drofjping device for the purpose of introducing sulphate of 

 alumina in the water-supply tank, in varying amounts to meet the 

 requirements, the turbidity of the spring water was greatly reduced, 

 most of the sediment being precipitated to the bottom of the tank. 

 This greatly lessened the work of caring for the eggs and fry and 

 it is believed to have averted a large loss of fry, especially of the 

 brook trout, which do not appear to be able to survive roily water. 

 Considerable trouble was caused by the development of " pop-eye " 

 among one lot of rainbow trout that had been held in water taken 

 direct from the spring, but on transferring them to troughs con- 

 taining water supplied by the filter the disease lessened and gradually 

 disappeared. 



The efficiency of the station was greatly increased during the year 

 by the installation of 18 newly constructed troughs in the' old 

 hatchery building and arranging them so that the water supply 

 can be drawn either from the filter or direct from the sprmg. 

 These troughs have a capacity for 1,000,000 trout eegs, 750,000 fry, 

 or 180,000 fingerlings No. 1. 



The new hatchery has two hatching rooms. The one in the base- 

 ment is equipped with 20 troughs arranged in a single series on 

 iron-pipe supports, each trough being 13 feet 5 inches long, 14 

 inches wide, and 6 inches deep. The room on the floor above con- 

 tains -10 troughs arranged in two series, and the water supply, which 

 may be taken either from the filter or direct from the spring, is 



