436 BULLETIN OP THE BUREAU OF FISHERIES. 



Of a large number of yearling landlocked salmon held in a small pond, 102 were 

 examined. Seven fish were affected, three having red floors and four visible tumors. 



There is nothing extraordinary about the conditions at Lake Auburn hatchery, which 

 shows rather a typical case of the endemic occurrence of the disease. Here are spring 

 water, dirt ponds, the common proteid foods, liver and heart, and adult fish in excellent 

 condition from the ordinary fish cultural standpoint, and with no unusual mortality 

 rate, but a considerable morbidity in visible thyroid enlargement, with immunity of 

 the brown trout. 



At two other State hatcheries similar or greater morbidity has been determined 

 from actual examination, and reports from superintendents of both Federal and State 

 hatcheries indicate the general extent to which these conditions obtain, with some few 

 exceptions, throughout the territory of trout culture in the United States. 



PRIVATE HATCHERY IN THE STATE OF WASHINGTON. 



At North Yakima, Wash., an interesting and instructive example is afforded of 

 endemic occurrence among young trout at a newly established private hatchery where 

 30,000 brook trout were held in earth trenches supplied by spring water. The food for 

 the first six months was liver, after that horse meat. The hatchery was started in 

 March. In the following December, before the trout were a year old, thyroid tumors 

 were observed among them, about i per cent being affected. The several specimens 

 we have examined show tumors which, relative to the size of the fish, are among the 

 largest we have seen. One of these was 13 millimeters in diameter in a trout 8.5 centi- 

 meters in standard length. Microscopically the structure shows solid carcinoma, 

 among the most malignant of our examples. 



Rainbow trout of the same age and living under exactly the same conditions at 

 this hatchery are not affected with thyroid tumors. The region in this part of the 

 State is said to show a high percentage of goiter among female children and among calves 

 and other domestic animals. Statistical studies, however, have not been made. 



This instance shows an unusual acceleration of the thyroid process. Malignant 

 carcinoma of large size developed in trout under i year of age and during the first year 

 of a fish hatchery. Obviously domestication of long duration, either in the individual 

 fish or in the local station where the fish are held, is unnecessary. Something local at 

 this particular fish hatchery seems to be concerned in the unusual result. Certainly 

 the general conditions of trout culture as expressed at the numerous stations where 

 trout are bred do not result in the rapid course of disease here shown. Is there merely 

 a local intensification at this hatchery of the essential cause of the disease? 



EPIDEMIC OCCURRENCE. 



The hatchery at Bath, N. Y., referred to in the introduction as having first 

 attracted our attention to this condition, was, up to 1907, free from visible tumors. 

 From the accompanying diagram (fig. 81) it will be seen that the water supply of this 

 hatchery comes from a large pond (A) fed by several springs on land adjoining the hatch- 



