202 Transactions. — Zoology. 



waited for the ''troubling of the water." Being unable then to fulfil the 

 functions of nature at the spawning season, is the first contributing cause 

 to the outbreak of the fungus. 



Again the chemical constituents of the water have an important bearing 

 on the health of the trout. Trout under domestication when attacked by 

 fungus have in almost all cases been cured by the addition of common salt 

 to the water supplying the ponds or tanks containing the fish, provided the 

 disease has not been permitted to go too far. As already mentioned, Dr. 

 Black reports that the Wakatipu water has less salt in solution than any 

 water. ever examined by him. Now, as salt is an essential to health in 

 trout, its entire absence in the water under consideration must act pre- 

 judicially on these fish. This is the second and only known cause tending 

 to accelerate the outbreak of the disease. But there is yet another cause 

 which I suspect, although not in a position to prove, namely, — the absence 

 of a clue proportion of oxygen among the gases held in solution by the 

 water. To determine this, not only is a gaseous analysis required, but it 

 is also necessary to find out what that quantity of oxygen is which trout 

 require. Science has yet to discover this ratio so far as I know, and it is 

 an important element in its bearings on this question. As already stated, 

 the fact of the trout seeking those places, as the mouth of the creek and the 

 reef, where oxygen is likely to be most abundant owing to the constant 

 agitation of the water, shows that the instincts of these trout teach them to 

 look for water where the best aeration is to be found. 



These causes, then, seem to me sufficient to prove that the disease 

 among the Wakatipu trout has been consequent on functional derangement, 

 and that this has so lowered the vital force of the fish as to leave them 

 powerless to resist the attacks of the fungus, a plant which the best authori- 

 ties tell us is present in all fresh waters. 



Can the Disease be cured in the Wakatipu Fish ? 



And here I confess that, considering the unfortunate situation of these 

 trout in Queenstown Bay, no ordinary remedy could be applied efficiently. 

 For although the submergence of rock salt at the places frequented by 

 the fish, and the artificial increase of tire water supply to the Town 

 Creek, might probably lessen the extent of the evil, yet these applica- 

 tions could effect but a partial and temporary check on the disease. 

 Moreover, there would be no finality to these operations, and their 

 cost would exceed the means of the local Acclimatization Society I 

 fear. No doubt it would assist if the trout were netted and all affected 

 fish killed and burned; but in this there might be no finality either, 

 still it ought to be done. While I am bound then to admit that I see 

 no specific cure of an easy and cheap nature, there is yet hope, I think, 



