Arthur. — On the Brown Trout introduced into Otago. 501 



out of their stomachs, as related by me above, and they are known or sup- 

 posed to have killed and eaten trout about 2 lbs. in weight. The ordinary 

 shag of our rivers is about as big as a tame duck, but much thinner in body 

 having a long sinewy neck and a dreadful bill with a hook at the point. 



Disease at our Opoho hatchery among the ova is unknown. Dead eggs 

 have been found to be unimpregnated, and no loss has resulted from silt, of 

 which there is always a good deal. Deaths among the young fish have been 

 consequent on a dropsical affection of the umbilical sac, and of monstrosi- 

 ties. Having already made some remarks on very thin male trout which 

 appeared to be " dying by inches," in consequence of their flesh and fat 

 consuming away, I will not add more than the suggestion that fever would 

 account for the symptoms or effects of their ailment. Several specimens 

 of trout found dead in our rivers have come under my notice. Dissection 

 showed that some internal organ as the intestine was ruptured, but how oc- 

 casioned it would be hard to say. For several years Mr. Nelson has seen 

 trout in Lovell's Creek which were quite blind. This he proved repeatedly 

 by trials ; yet when a worm or bait was thrown into the water they took it 

 at once. These trout were of both sexes, 4-5 lbs. in weight, not by a long 

 way the largest trout in the stream, and their eyes had white opaque spots 

 on each. In the case of females, the ova were found at the spawning season 

 to be bad, although the fish were in good condition. No cause has been 

 found out for this singular eye affection, but probably its origin is parasitic. 

 Fungus, unfortunately, is not unknown in Otago waters. It was noticed 

 first on trout in confinement at the Wallacetown ponds, by Mr. Howard, 

 about 1874 or 1875. During spawning it has been seen on trout in Fulton's 

 Creek ; but in Queenstown Bay, Lake Wakatipu, it is very prevalent among 

 the shoals of trout there, as formerly described by me.* The pathology (to 

 borrow a medical expression) of this disease has not yet been worked out 

 exhaustively, and it is surrounded by many difficulties. At the same time 

 I may be pardoned if I again give my opinion, that all the exciting causes 

 of the affection may be narrowed down to two conditions, viz. : — the absence 

 of sufficient salt in the water inhabited by the fish, and of sufficient oxygen 

 in the blood of the fish itself. Salt has been found to be a wonderful health 

 promoter among the Salmonidas ; and oxygen, in the necessary proportions 

 in the blood of the fish, is indispensable to secure it from fungoid attacks. 

 Trout in Shag Eiver have died, as supposed, because of excessive heat. 



HI. — Structure. 



Although external colour and markings can scarcely be referred to struc- 

 ture, yet these come more naturally under that heading than any other. 

 Specimens of trout from High Wycombe, Bucks, are thus described by Mr. 



* Trans. N.Z. Inst,, 1882, vol. xv., p. 198. 



