278 BULLETIN OF THE BUREAU OF FISHERIES. 



the river quickly swim away and are seen no more proves nothing. The disease would 

 not be evident for two or three days in any case. 



In order to determine the prevalence of the disease among rescued fishes a long 

 series of experiments will be required, but owing to the limited time at the writer's 

 disposal only a few preliminary experiments have as yet been carried out. In these 

 experiments a special effort was made to duplicate so far as possible the average condi- 

 tions found in rescue work. The fish were seined from small, isolated ponds, one of 

 which is shown in figure 259, and then carried in washtubs to the river, where they were 

 placed on a launch to be carried to the station. These fish were in the tubs from one-half 

 to one hour, which the writer was assured by the fishermen is somewhat less than the 

 average time they are held in tubs in ordinary rescue work. On reaching the station 

 the fish were at once placed in an inclosure surrounded by fine-meshed poultry wire. 

 This inclosure (fig. 258) was constructed in shallow water along the river shore and was 

 sufficiently large to obviate any danger of the fish being crowded. A small stream 

 carrying the overflow from the fishponds flowed into the inclosure, so there was a good 

 supply of running water at all times. The cross partition shown in the figure was added 

 later for some special experiments which are not considered in this paper. It is believed 

 that the fish held in this inclosure were in fully as favorable an environment as they 

 would have been if liberated in the river. 



Experiment No. 6. — September 2, 1919, 42 buffalofish, 41 crappie, and 8 bluegill 

 were seined from the pond shown in figure 259. This pond was believed to be typical 

 of those from which fish are taken in rescue work. It was about 400 feet long by 100 

 feet wide and quite shallow, being not over 3 or 4 feet in depth at the deepest part. The 

 bottom, as in most ponds of this kind, was composed of fine, soft mud. The tem- 

 perature of the water at the time the fish were removed was 83° F. All the fish 

 appeared in 'good condition when placed in the inclosure. The next day (Sept. 3) 

 six crappie were found dead. Since no bacteria could be found on these fish they are 

 believed to have died from injuries due to handling. September 4 one badly diseased 

 buffalofish was removed, and the next day there were two dead buffalofish, both with 

 well-developed lesions. The inclosure was seined on September 6 and all thefish removed. 

 Only four dead fish were found, three buffalofish and one crappie. However, many of 

 the living fish were badly diseased and in all probability would have died in a short time, 

 but it was not thought best to leave them in the inclosure longer, since there was 

 great danger of the disease spreading from the infected to the healthy fish. It is not 

 believed that any of the fish which are classed as infected at this time had contracted 

 the disease in this way, since all were in advanced stages of the disease. The diseased 

 fishes included 1 9 buffalofish and 10 crappie. They were removed to aquaria well supplied 

 with running water, but all died within 24 hours. It is believed justifiable to assume 

 that all the fish classed as diseased became infected as a result of the treatment to which 

 they had been subjected and would have eventually died if set free in the river. 



