Nos. 61S-619] RESTOCKING INLAND WATERS 



349 



lined. It is unnecessary to say that many thousands of 

 dollars' worth of fish would be rendered available through- 

 out the United States, if this one disease alone could be 

 prevented. Perch and bass which are so generally in- 

 fected with Trematodes are delicious pan fish and usually 

 easily caught in large numbers. It would seem as if the 

 mere calling attention to this large amount of food an- 

 nually wasted would stimulate some organization to 

 finance the necessary scientific investigation. Such an 

 investigation would need to continue at least two years 

 and possibly longer; but the expense involved would be 

 a small fraction of the returns, if the disease could be pre- 

 vented. 



"Grubby" perch are but one illustration of the diseases 

 that occur in our fresh-water fish. There are a number 

 of diseases due to bacteria and others caused by certain 

 Soporozoa, Fig. 7. These diseases are usually epidemic, 



killing large numbers of fish in a few weeks. The main 

 fact that is known now is that the fish die and several 

 specific microorganisms are observed to be associated 

 with certain ulcers, cysts, etc. But as to what causes 

 lead up to the fatal termination of the diseases, little is 

 known. 



An admirable monograph upon carcinoma of the 

 thyroid in the Salmonoid fishes was prepared, but left in- 

 completed because of lack of funds. This is about the 

 only serious study of fish diseases that has been made in 

 the United States. 



At this time, when all are anxious to help in whatever 

 way that they can, it may be permissible to suggest that 



