390 XJ. S. BUREAU OF FISHEEIES 



of these trips was to review the entire system of trout propagation 

 and management in the State. Special attention was paid to the 

 prevalence and control of disease among hatchery fish. At the end 

 of the season a report was prepared on the operation of the indi- 

 vidual trout hatcheries based on actual observations and on a 

 questionnaire sent to all hatchery superintendents. 



In order to facilitate the study of diseases which are becoming a 

 serious problem in many trout and salmon hatcheries in the West 

 it was decided to install a pathological laboratory at the Fisheries 

 biological station in Seattle with Dr. Fish in charge. The need for 

 such a laboratory is very evident since there are reasons for believing 

 that in addition to most of the diseases which affect trout at Eastern 

 hatcheries there are other diseases which are peculiar to this region 

 or at least have not yet been found at Eastern hatcheries. 



Experiments have been conducted looking toward the improvement 

 of methods of treating fish in pools by allowing a very dilute chem- 

 ical solution to flow into the pool at a uniform rate. Solutions of 

 potassium permanganate, copper sulphate, and chlorine have been 

 recommended for this purpose, but in no instance have the methods 

 yet devised proved entirely satisfactory. It has been found ex- 

 tremely difficult in practice to treat fish in pools with such solutions 

 without serious danger of kilhng large numbers of fish. In some 

 instances very satisfactory results have been obtained, but in other 

 cases heavy losses have occurred wlien using the same treatment. It 

 is believed, however, that these difficulties can be eliminated largely 

 by further experiment in the technique of treatment. 



An experiment to test the value of iodine as a cure for furunculosis 

 was carried out at the Pittsford station. For this purpose a lot of 

 yearling California golden trout, which are quite susceptible to the 

 disease, was divided into two equal lots and placed in small circular 

 pools. Before beginning the experiment these fish had been showing 

 a small daily mortality from furunculosis for some time. One lot 

 was used as a control, the other lot was placed on a diet containing 

 salmon oil and a solution of iodine according to the recommenda- 

 tions of E. R. HeAvitt. The experiment was started August 10 and 

 for the first 13 days the losses in both lots were approximately the 

 same. The total losses on August 23 were 46 in the lot given iodine 

 and salmcn oil, and 47 in the controls. The supply of salmon oil 

 was exhausted on that date and the iodine solution soon after, but 

 the experimental lot was kept on a dry diet supplied by Mr. Hewitt 

 for a month longer. During this period the loss among this lot was 

 appreciably less than among the controls. The experiment was dis- 

 continued on September 22 at which time the losses among the lot 

 on the Hewitt diet totaled 74 and among the controls 144. 



While these results show approximately twice the mortality among 

 the controls as among the fish kept on the Hewitt diet, it is by no 

 means demonstrated that this difference was due to the inclusion of 

 iodine or salmon oil in the food. As a matter of fact, the supply of 

 both of these constituents was exhausted at about the time the fish 

 began to show improvement, and the decreased mortality among the 

 experimental lot may easily have been due to other causes. In 

 previous experiments marked differences in mortality from furuncu- 



