Fish diseases

This historic book may have numerous typos, missing text or index. Purchasers can download a free scanned copy of the original book (without typos) from the publisher. 1883. Not illustrated. Excerpt: ... LONDON, 1883. Conference On Tuesday, July 3, 1883. The Marquis Of Hamilton in the Chair. ON FISH DISEASES. The title of the present paper is, I am sorry to say, far too large for its contents, for I propose to speak, not of fish diseases in general, but of that particular malady which attacks freshwater fishes, occasionally assumes the dimensions of a very formidable epidemic, and, in one of its forms, the so-called "Salmon disease," is too well known. At the first onset of this disease, small whitish patches make their appearance on the skin of the fish. The smooth integument of the top of the head, or of the end of the snout, is a very usual locality, but the adipose fin, and the axillae of the paired fins are also among the first parts to be affected. If there is an abraded or wounded surface, the disease is pretty sure to attack it, but the invasion of the malady is in nowise dependent upon the pre-existence of an injury. In severe cases, the mischief rapidly extends, until sometimes almost the whole body is covered with an ashen grey coat, which completely hides the scales. On brushing off the crust, however, the scales are usually found undisturbed. In the scaleless parts of the skin, sloughing soon sets in, and deep burrowing sores are formed. On the head, the cranial bones may be exposed, and the fins are eaten away, and become ragged. Very often one or both gill-covers become partially glued down to the shoulder, and the gill-openings obstructed, but I have never yet been able to meet with any sign of disease on the gills themselves. This is contrary to common belief, but I can only say that such is my experience. On the other hand, the disease frequently invades the cavity of the mouth, and often more or less destroys ...