CANCER IN TROUT.

New Zealand Herald, Volume XLI, Issue 12555, 22 April 1904, Page 6

CANCER IN TROUT.

INTERVIEW WITH MR. AYSON;

THE DISEASE CONFINED TO

HATCHERIES.

Advantage was taken of the presence of the chief inspector of fisheries (Mr. L. F. Ayson) in Auckland to interview him with regard to cases of cancer discovered in trout, as the discovery might occasion some alarm in the minds of sportsmen, alarm which, it is satisfactory to' state, may be at once dispelled. • Mr. Ayson said the discovery was not a new one, and he was good enough to outline the history of it. " I first noticed this gill disease in 1890, among the American brook trout (Salvelinus fontiualis) t at the Masterton trout, hatchery. The disease was at first peculiar to this fish until the rainbow trout (Salmo iridens) were introduced, and among them it made its appearance when the fish were three years old. I have neve; found any in the English brown trout. (Salmo faiio), but I found three Loch Leven trout (Salmo levenonsis) affected in 1896. These fish were all from three to four years old, and the three were collected from" 1000 fish taken in 1896. In 1898 about two per cent, of the American brook trout over three years of age would be affected/and about, one per cent, of rainbow trout over that aye.' " Have you ever found any fish affected under three years of age?" " No, and I have no record of fish having been affected under that age. I wish you to understand very clearly that it is only the fish kept in hatcheries that have been found, so far as I know, suffering from this disease, and that all diseased fish not kept for specimens are knocked on the head and destroyed when they have been taken. I have'never known a case of brown trout being affected, and I should most, certainly have been the first to be informed of 'such a case. I think Mr. Cheeseman has stated that 'ho had not heard of any cases occurring in the bush in fish in the wild state in the Auckland district, although he believed such cases had occurred in tho South, where the disease had been more troublesome among the brown and brook trout, which were possibly more subject to the complaint than the rainbow trout.' Now, as a matter of fact, as I have already said, 1 never heard of a single case of brown trout being affected, and not a solitary instance of the disease occurring in wild iish either in the South or the North Island; no case, in short, except among fish confined in the hatcheries, fish that are kept there for bleeding purposes. The largest percentage of the fish affected were the rainbow trout and tho American brook trout."

- " And to what do you attribute the disease among the fish you have specified, and which are stock fish, kept at the hatcheries*/"

"It is, I believe, due to the artificial life that they lead, to artificial food, tho principal part of which is minced sheep's plucks and bullock's liver." " Can you establish any connection between the disease and this food?"

"Well, at the Government salmon hatcheries at Hakateramea, a certain proportion of sheep's plucks are used, but a considerable part of the food used is a patented preparation made from the flesh of certain sea fish imported from Home. So far there has been no appearance of the disease among the salmon there. We have sent some of this food to be used by the Otago Acclimatisation Society in their hatcheries." '"Is not your discovery likely to be of considerable service in the elucidation of cancer, the cause of which, when known, is considered to be the first step towards its cure?"'

" It is impossible to say how important. a bearing this discovery of cancer in brood trout may have on this vast subject. You will have seen that Mr. Gil ruth, the Chief Government Veterinarian, has already sent specimens of the affected parts of fish to Dr. Bashford, director of the Cancer Research Fund, in England, and some affected trout have been sent to Dr. Bashford, preserved in ice. It is impossible to foretell at this stage the important issues hanging upon this investigation, not only for New Zealand, but for the whole world. So far as we here are : immediately concerned, I would conclude with a summary of my remarks: (1) That the disease has not'been found among fish in the wild state; (2) that it is confined to the' hatcheries ; (3) that no case has been found among the English brown trout; (4) that it is chiefly American brook trout and next rainbow trout that are affected; (5) that only three instances of Loch Leven trout have been brought to my notice—and lam certain to have heard of other cases of any disease sooner or late ; and (6) that no "fish have been found diseased under three years old."