FISHERIES AT LAKES TAUPO AND ROTORUA (REPORT ON), FROM 1st JUNE, 1914.

Appendix to the Journals of the House of Representatives, 1915 Session I, H-21

H.—2l

1915. NEW ZEALAND.

FISHERIES AT LAKES TAUPO AND ROTORUA (REPORT ON), FROM 1st JUNE, 1914.

Presented to both Houses of the General Assembly by Command of His Excellency.

Department of Internal Affairs, Wellington, 26th July, 1915. Memorandum for the Hon. the Minister of Internal Affairs. I have the honour to submit my second annual report respecting the fisheries at Lakes Taupo and Rotorua. J. Hislop, Under- Secretary.

Work done during the Past Yeah. During the year just ended work in connection with the fisheries has been carried on systematically at Rotorua and Taupo. While, as in the past, the primary object has been the improvement of the fishing in the lakes, careful attention has been been paid to all phases of the work, which may be grouped under the following heads : (1) Destruction of ill-conditioned fish ; (2) marketing of fresh and smoked trout; (3) procuring fresh food-supplies ; (4) study of the worm parasite in trout; (5) destruction of shags ; (6) trout-hatchery. (1.) Destruction of Ill-conditioned Fish. Immediately after the close of the fishing season 1913-14 the work of thinning out illconditioned fish was again undertaken, and carried on from the 1st June to the 31st October. At Taupo the numbers taken and destroyed were greatly in excess of last year's totals, not on account of the fish being in poorer condition, but because the rivers being lower than usual better facilities for netting were provided. At Rotorua a greater number of fish was handled than during the same period of last year, but the majority being in much better condition than usual they were placed above the barriers to spawn. The total number taken and destroyed was — Number. Tons owt. qr. lb. Rotorua Lake ... ... ... ... ... 11,263 10 1 0 14 Taupo Lake ... ... ... ... 11,216 20 0 2 8 Totals ... ... ... ... 22,479 30 1 2 22 During the fishing season, 1st November, 1914, to 31st May, 1915, ill-conditioned fish taken from the fish netted for market and destroyed numbered— Number. Tons cwt. qr. lb. Rotorua Lake ... .. ... ... ... 3,678 10 13 118 Taupo Lake ... ... ... ... ... 1,563 6 19 3 19 Total ... ... ... ... 5,241 17 13 1 9 (2.) Marketing of Fresh and Smoked Trout. The following statements show the business of the open season 1914-15 at the Rotorua and Tokaanu Depots : — Number. Tons owt. qr. lb. Rotorua ... ... ... ... ... 28,460 18 3 3 6 Tokaanu ... ... ... ... ... 11,574 22 6 2 6 Total ... ... ... ... 40,034 40 10 1 12

H-.—21

2

Netting operations were carried on during this period at such times and places as would not interfere with sportsmen, and the catches were limited to the numbers deemed desirable to be taken from the lakes for thinning-out purposes. The success attending the marketing of fresh and smoked trout led to the presentation of several requests for permission to be granted to residents of Taupo to sell fish, but all were declined, it being considered that the granting of such permission would lead to an undue depletion of the fish in the lake, thus defeating the real object of the Department's operations—namely, the improvement of the fishing. ' ; ' During the season considerable quantities of fish were sent to the officers and men at the Trentham Camp and to the Maori Expeditionary Force at Avondale. (3.) Procuring Fresh Food-supplies. Continuing the work of last year, shrimps to the number of 342,000 caught in the Waikato River at Mercer have been liberated in Lake Rotorua at places where they have a fair chance to multiply. (4.) Study of the Worm Parasite in Trout. It was alleged a short time ago that cooking did not kill the parasite, and to settle doubts on this matter Dr. Wohlmann, Government Balneologist, of Rotorua, was asked to make some practical experiments. He reported as follows : — " Department of Tourist and Health Resorts, " Rotorua, 30th January, 1915. " As requested, I have experimented as under with the effects of cooking on these parasites, and find that with ordinary cooking they are killed. lam not sufficiently acquainted with their lifehabits and their mode of reproduction to be in a position to state positively that there is no danger whatever in their presence in cooked food, as I do not know whether they may have eggs which may be peculiarly resistent to heat, but such a contingency is so exceedingly improbable that I have dismissed it from further consideration. There is one point worthy of note in Experiment 11, as it may explain the belief that the parasites are not killed by cooking : on removing the dead parasites from the body of the fish they curled up to a certain extent as if they were alive. This was due to shrinkage of their elastic bodies on removal from the tissues supporting them. " Experiment I. —Two large parasites were placed in a test-tube, boiling water poured in, and the tube kept at the boil for thirty seconds. At the end of that period both were dead, and no signs of life were discernible after being kept for twenty-four hours in normal salt solution. " Experiment II. —A ' slab ' trout of about 1 lb. weight was cut open, and the digestive tract found full of living parasites. The carcase was bound up securely in string, and boiled for twenty minutes by the Sanatorium cook in the ordinary way as for the table. The fish appeared cooked to the ordinary degree, and, on opening, the parasites were dead. " Experiment III. —A similar fish was opened, and the digestive tract found full of living parasites. The carcase was tied up in paper to prevent escape of contents, and fried in the usual way. The parasites were found to be killed. "In none of the fish examined by me were parasites found in the muscular tissues. This was perhaps unfortunate, in view of the completeness of the experiments, as it might be said that worms in such a situation would be more protected from the effects of boiling water, but by wrapping up the parasites in the carcase of the fish I protected them in my experiments as far as possible, and I have no hesitation in saying that all worms are killed by ordinary cooking. " Arthur S. Wohlmann, " Government Balneologist." Owing to the war it has not been possible so far to spare a Biological officer to proceed to the various points on the sea-coast where there are no trout, to ascertain if shags on the coast are infested with the parasite. The experimental ponds established at Rotorua have been maintained during the past year. The following report of the work done during the year has been furnished by the Director of the Live-stock and Meat Division of the Agricultural Department who is in charge of the experiments: — " I regret that owing to the outbreak of war, which necessitated a number of the veterinary officers of the Department leaving New Zealand with the Expeditionary Forces, and that consequently a great amount of work had to be thrown upon those remaining, as well as upon myself, it has been found impossible to make the progress with this special work which I would have liked. As you are aware, since Mr. Kerrigan, Veterinary Inspector, left Rotorua I have largely carried out the work myself, with the assistance of Mr. Collins, Veterinarian, of Hamilton, but I have been kept closely tied to headquarters, while Mr. Collins's duties have been greatly increased. " The experiments undertaken with trout and toi-toi iv the ponds adjacent to the Rotorua Sanatorium have been in progress for several months, and, so far, have given absolutely negative results. In the one case where healthy trout from outside were placed in the pond and fed with toi-toi from the lake no indication of ill health has been shown by the trout; on the other hand, those toi-toi which have been examined after being secured from the lake have in every case proved to be free from infection by the parasitic worm which is responsible for the trout trouble; hence our experience on this point has been rather disconcerting, seeing that the experiment was undertaken in the hope that affected toi-toi would be found, and that the trout in the pond would become infected in turn through feeding upon them. In the other case where a number of small fish were obtained from the Waikato River, at Mercer, and were placed in a pond over which two shags were caged, none of these small fish have been

3

H.—2l

found affected. One of the shags died, and on post-mortem examination was found to be harbouring a large number of worm parasites, which, however, had nearly all died, and were undergoing degenerative changes. The position regarding this shag is shown in the accompanying copy of a memorandum sent to the Conservator of Fisheries, Rotorua. " It is a matter for regret, therefore, to have to report that no further tangible advance in our knowledge of the trouble affecting the fish has been made. My opinion, however, regarding it remains unaltered. "0. J. Reakes, D.V.Sc, M.R.C.V.S., Director, Live-stock and Meat Division. " 23rd December, 1914. " The specimen from the large black shag arrived yesterday, and was examined by myself and Mr. Kerrigan, who happened, fortunately, to be in Wellington. The following is the result of the examination : Stomach itself is free from parasites, but pyloric end of duodenum shows great chronic thickening of wall, with masses of what are evidently degenerated parasites embedded in it. Only one parasite found, which was evidently living at time shag died. This was also in pyloric wall. " I note that you intend to replace the birds as soon as possible with other of the same species. The sooner this is done the better. You will remember that we have been wanting another shag for some time. There is one point in connection with the feeding of these shags which requires very careful supervision—namely, that the worm-infested trout used for feeding them should be given to the shag as soon as possible after the fish have been caught. Though the worms are found alive for some time after the fish dies, yet their vitality is doubtless progressively reduced as time goes on. Moreover, it must be borne in mind that it is only when the worm has reached the proper stage of development in the trout that it is capable of taking up its abode in the shag, and there completing its cycle of existence. " C. J. Reakes, D.V.Sc, M.R.C.V.S., Director, Live-stock and Meat Division. " F. Moorhouse, Esq., Conservator of Fish and Game, Rotorua." (5.) Destruction of Shags. During the past year 2,064 shags have been accounted for to the Conservator of Fish and Game, and during the coming season further efforts will be made to rid the district of these birds. (6.) Trout-hatchery. The value of the Government hatchery is becoming more apparent as times goes on. Not only are the fisheries within the Rotorua district stocked from it, but it is proving of the greatest value to the acclimatization societies, who at little cost can obtain supplies of first-class rainbow ova, fry, or yearling fish. The following statement shows the work done for the year : — Number of rainbow-trout ova sold and distributed ... ... 1,135,000 Trout-fry liberated ... ... ■•■ ... ... ... 775,000 Yearling trout sold ... ... ... ... ... ... 200 Total ... ... ... ... ... 1,910,200 The trout-fry was liberated not only in rivers and streams throughout the district, but also in the rivers in the Tongariro National Park, in the Waimarino district. The demand for rainbow ova from the hatchery is not restricted in New Zealand, large orders from New South Wales being filled during the season. Gifts of ova have been made to some of the smaller acclimatization societies.

Approximate Cost of Paper.—Preparation, not given ; printing (750 copies), £2 15b.

Authority : John Mackay, Government Printer, Wellington—l9ls

Price 3d.)