56 The Fungus of Salmon Disease. 



no injury during the spawning periods. Such a summer out- 

 break can hardly be considered an epidemic, though with a 

 continuance of these unfavourable conditions for the fish, it 

 may eventually develop into one. 



Since attention has been drawn to the subject, it has been 

 shown that isolated instances of the same disease causing death 

 (generally during the winter months) are not uncommon, and 

 are still frequent even in rivers where the epidemic form is un- 

 known ; and it is likely that such isolated cases of death among 

 salmon from fungus have always occurred, and in all probability 

 always will occur. 



It is of interest to know that the salmon disease is not con- 

 fined to Great Britain. In a letter that appeared in the Field 

 many years ago, a description was given of it as occurring in 

 the most virulent form in Siberia. The observer, Commander 

 Stuart, of the Navy, reports that in a river running into Cas- 

 tries Bay he saw thousands of dying salmon in all the stages of 

 disease. He acids that they presented the usual appearance, 

 and were covered with fungus. Such was their condition, that 

 when he was wading in the river they did not even attempt to 

 swim away, so that he could have killed them with a stick. I 

 also am informed of a lake in Russia where the disease appeared 

 and nearly killed all the fish. In this instance the fish were of 

 the coarse kind — perch, pike, soam, and I suppose carp, which 

 are very common there. 



The appearance of the disease on a fish is first marked by a 

 greyish spot, generally of a round shape, and if it be situated 

 on the dark skin of the head or back it is easily observable. I 

 have often watched the fungus growing from a favourable posi- 

 tion, and it is astonishing how rapidly it will spread, by fresh 

 growth at the edges. The fine threads or stems of the growing 

 fungus form a kind of halo round and enclosing the spots by 

 their standing out into the water. On a fully developed 

 patch of the disease, these filaments will protrude for more 

 than an inch into the water, growing as thickly as they can 

 stand. The fish, when diseased, often rush madly about, and 



