CXLIV REPORT OF COMMISSIONER OF FISH AND FISHERIES. 



MISCELLANEOUS MATTERS. 



Fish ova for educational purposes. — The Commission has from time to 

 time received requests for fertilized fish eggs for use in biological 

 courses of schools and colleges. Such eggs are very acceptable objects 

 of study, especially during the colder months, when other material is 

 scarce; and as they can be furnished at an inappreciable expense, the 

 Commission has been pleased to accommodate applicants. With a 

 view to increase the aid that might thus be given to biological work, 

 it was decided, in the fall of 1898, to make the fiict more generally 

 known among educational institutions that living fish-eggs, in small 

 quantities, would be supplied on request. Accordingly, a notice was 

 published in Science, stating the conditions under which eggs would 

 be sent, the stations at which they were incubated, the kinds of eggs 

 at each station, and the season when available. A number of univer- 

 sities and schools took this opportunity to obtain class material. 



Investigation of trout epidemic at Northville, Mich. — About the middle 

 of October, 1898, a very disastrous epidemic broke out among the 

 yearling brook trout {Salvelinus fontinaUs) at the Commission's station 

 at iSTorthville, Mich., and continued for three months, during which 

 time upward of 3,000 fish died, or about 32 per cent of the total number 

 in the affected ponds. The epidemic was first investigated by Mr. M. 0. 

 Marsh; later, when it became necessary to assign Mr. Marsh to other 

 duties. Dr. 0. M. Blackford, jr., took up the inquiry. 



The affected fish had been hatched in the preceding spring and were 

 previously in good condition. The earliest symptoms of the disease are 

 sluggish movements and inability to keep u}) with the other fish of the 

 school. Later, they remain close to the bottom and are almost motion- 

 less, a slight fanning movement of the pectoral fins being the chief indi- 

 cation of life. As the disease progresses the gills are involved in a 

 large proportion of cases and breathing becomes difficult, the fish going 

 to the surface and gasping for air. The power of maintaining equilib- 

 rium is gradually lost, and the fish turns on its side, and the effort to 

 regain the upright jiosition may carry it past the center and cause it to 

 roll over and over as it swims. 



The characteristic lesions are effusions of blood in the subcutaneous 

 tissues and between the muscles; and frequently, but not constantly, 

 an inflammation of the gills leading to bulging of the opercles, and 

 inflammation and softening of the heart and large blood vessels. The 

 areas of extravasated blood occur upon all parts of the body, but most 

 commonly at the bases of the fins, varying in size from a mere speck to 

 three-fourths of an inch, larger spots sometimes being formed by the 

 confluence of several small ones. Should the fish live long enough these 

 effusions undergo degenerative change, with tlie formation of pus and an 

 abscess cavity. In time the abscesses reach the surface and discharge, 

 leaving a deep ulcer witli pockets and sinuses extending in various 



