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Part III. — Seventh Annual Report 



disease prospered but little, but towards the end of October in the same 

 year great quantities of salmon lying in the pools below Brechin were 

 badly marked with it. He considers that the disease usually gets less 

 toward the latter end of January and at this time clean spring fish 

 passing up the river are seldom touched with the fungus. He further 

 notes that the practice of 'sniggering,' adopted by certain people, by 

 which process a hook is allowed to sink into a pool in which fish are 

 collected and then dragged about forcibly with the intent to foul-hook 

 fish, is well calculated to promote the extension of the disease. He 

 bases this theory on the fact that many of the diseased fish obtained by 

 him were marked by cuts, which might have been thus inflicted. The 

 South Esk is this year almost entirely free from salmon disease and the 

 same applies, but in a less degree, to the North Esk. The lessees 

 attribute the freedom from disease to the fact that the river has through- 

 out had plenty of water. 



As far as we can learn the earliest recorded observations of such a 

 disease affecting fish are those of Unger's,* who described a fungoid 

 disease which occurred among some carp, confined in a pond in the 

 Botanical Gardens at Gratz. The fungus in question has been styled by 

 him as the Achyla prolifera, but there seems to be little doubt, from his 

 description, that it is a Saprolegnia. It must, however, remain questionable 

 whether or not it is really the S. ferax. In one of Mr Stirling's papersf 

 he gives a very interesting account of a disease which occurred at 

 Ightham, in Kent, affecting dace, roach, gudgeon, small perch, and small 

 pike, in which, however, the direct cause of death seemed to be suffoca- 

 tion from the fungus clogging up the gill openings. Ulceration here was 

 not a marked feature, but when it occurred it was found to be in those 

 situations most densely covered with the fungus. The eels present in the 

 moat and ponds always escaped the disease, although living in the midst 

 of the diseased fish. I have had numerous accounts given me of a 

 disease somewhat similar, if not absolutely identical, occurring among fish 

 kept in aquaria. There seems little doubt, as is noted by Professor 

 Huxley, but that salmon disease occurs frequently in a sporadic form in 

 many rivers, but it is still questionable whether like fungoid diseases 

 attacking other fish are exactly identical with S. ferax. 



Fish affected with the disease in question are easily recognised while 

 in the water, as the patches of disease have a white or greyish appearance, 

 which contrasts most markedly with the dark skin on the rest of the 

 body. So much so is this the case, that one approaching the river side 

 where a diseased fish is lying, usually detects the presence of the animal 

 in the first instance by the appearance of the white diseased patches. The 

 earlier symptoms of disease are usually better marked while the fish is 

 still in the water, than when it has been taken out of it, and consists in 

 the appearance of small greyish patches, which if small are usually 

 almost completely circular. The first patches generally make their 

 appearance about the head, and frequently upon the snout, but other 

 cases frequently present themselves in which a patch may be seen first on 

 the adipose fin and about the tail, and I have even seen it confined to the 

 extreme tip of one of the pectoral fins. Mr Stirling believed that the 

 principal cause of the localisation of diseased patches on and about the 

 head lay in the fact that fish usually lie with their heads up stream, and 

 as the skin in this situation is liberally supplied with mucus, spores 

 coming down stream tend to adhere in this situation and there germinate. 



* ' Sur l'Achyla prolifera,' Ann. d. Sci. Nat. Bot., 1844. 



t 'Additional Observations on Fungus Disease of Salmon and other Fish,' Broc. 

 Roy. Soc, Edin., vol. x. 1879. 



