FRESH WATER LIFE

Evening Post, Volume CVII, Issue 48, 28 February 1929, Page 7

FRESH WATER LIFE

CURATORS' CONFERENCE

CAREFUL NOTES NEEDED

The conference of rangers, curators, and officials interested in tlio fresh water fisheries of the Dominion was continued yesterday.

The Chief Inspector of Fisheries (Mr A. E. Hefford) apologised for the absence of Mr. C. L. Ayson owing to a bereavement. 110 said Mr. Ayson's knowledge, as one born to fish culture, and with a life-long knowledge of it, would have proved valuable. His own connection with fresh water fish culture: was limited, but he tuid had the advantage of meeting many people connected with it, both here and in England, and it was from these interchanges of opinion that he could realise the advantages of a conference such as the present, which he hoped would bo tile first of a series at fixed periods. In the past, though there had no doubt been much valuable work done, curators and others had been working on their own, and had thus not been able to correlate their observations. He knew that their practical interest did not stop at producing eggs and fry, but went much further with the enthusiasm they all had to improve the streams and fisheries of tho Dominion. To get the full value of observations it was necessary to collate them, and to obtain also the experience of other countries. They could get a great deal of valuable help from people who were not fish oulturists,'but scientists. America had spent millions on its fish culture. A3 an instance of the value of careful study, and of the results obtained, be mentioned the investigations of a culturist in America and Canada. One man had gone carefully into the question of the ovi-duct in salmonidae, and his investigations had proved of greai value in stripping processes. He had shown that it was a mistake to take the fish by the tail, as it threw tho eggs into the chest of the fish. The exchange of results of investigations wa3 necessary to the best way of working. Different methods might prove the best in different localities and conditions. He quoted an old authority, 'Stoddart, Ss having carried out experiments in the ancient haphazard way. He took trout and placed them in three compartments, feeding some on worms, some on minnows, and some on flies. The worm-fed trout wero lean, the minnows, which were eagerly attacked, fattened the fish more, but the best results were from the fly food. This was an instance of incomplete records. It' tho weight, number, increase in weight, etc., of the trout had been recorded, as well as the quantities of the various foods eaten, then the investigations would have been more valuable. LOG SHOULD BE KEPT. Mr. Hefford urged them to keep a log-book of all they noted, with all particulars statistically noted. A bank did not balance its books from memory, and observations wero only valuable if fully recorded. As an instance of the valuable work dono by a Canadian culturist on modern lines, he gave the results of experiments with 50,000 trout fry placed in each of two streams, in enclosures sealed to other fish or fish foods. One pool, in a state of nature, wns examined carefully, and tho stomach contents of the various fish in it noted. Ono had cloven young trout in it, others less. Three months later the young trout remaining as the result of tho insertion of the fry were found to bo remarkably few, 96 per cent, of them having vanished. In the other stream, where tho cnclosuro had been almost entirely cleared of natural enemies, only 09.5 per cent, of tho fry were found as young trout, showing that even under such favourable conditions there was a great mortality. This was put down, as tho result of investigations, to cannibalism amongst the young trout themselves, tho bigger eating tho smaller, to the depreciations of half-a-dozen or so other fish left in the pond, to the feeding of herons, and even to the feeding of fowls from a neighbouring farm, which walked about in tho shallow edges. If the same care wero taken in investigations hero, tho result would bo valuable, lie quite understood that the curators had not tho time to spare from their other duties to undertake things on such a scale, but he mentioned the careful methods to show the value of exactness. Science was not. a matter of long words, but of accuracy. ilr. Purrutt road a paper on the importance of scientific investigations in relation to trout production and management, and puinlcd out that it w.-i.s futile to plant more fish in tho streams in New Zealand until they could be given more to eat. RAINBOW TEOUT. ' Mr. Anderson spoke of! the difficulties that had been found in keeping rainbow trout in somo tributaries of tho Manawatu, while they' wero found in others, though not to tho extent to which fry had systematically been put in. There were rainbow in tho tributaries of tho Makuri, and a fow in the Malcuri itself, but in tho Mauawatu, of which tho Mnknri was a tributary, it had been found impossible to keep rainbow. It was his conviction that tho mineral contents of streams had a great bearing on their suitability for rainbow. ]Ie suggested that the research branch of the Marine Department might make thorough investigations in this direction by analysing the waters to see what they lacked. Mr. Ycrex said that investigations I

were being made by the Department's officers at Rotorua and Taupo.

Captain Phillips addressed the conference on the advisability of co-opera-tion and co-ordination of results, and suggested the feeding of fry on young crustaceans instead of the customary ground liver. An address was given by Mr. J. S. Main (Tiinaru.). on the planting of streams, in which he demonstrated the use of his own invention, a machine very much resembling a seed drill, with pipes through which the eyed ova were put below the shingle in suitable places at the tails of pools, in either spring creeks or permanent waters unlikely to be flooded. The process was to dig a trench, and the machine was moved slowly back as tho ova were dcpositcrl, and covered by shingle freo from sediment.

Yesterday afternoon was devoted to a general discussion on stream planting methods, the depredations of natural enemies, the prevention of the pollution of streams, and tho protection of whitclit. In regard to the latter Mr. Hefford said that he was considering tho regulations for next season, and they could rest assured that a limit would, be put on the season, while the regulations would be altered in several ways to protect the whitebait, both in the interests of netters and the anglers.