SCIENCE & ANGLING

Ashburton Guardian, Volume 55, Issue 272, 30 August 1935, Page 8

SCIENCE & ANGLING

WORK OF RESEARCH COMMITTEE ADDRESS BY PROFESSOR PERCIYAL. An informative address on tho work of tho New Zealand Freshwater Research Committee was given at Dunedin by Professor Percival, who has charge of the work of the committee. Professor Percival said that the New Zealand Freshwater Research Committee had been set up in 1929 to investigate trout and other acclimatised fish in New Zealand, and it had to report each year to the annual conference of New Zealand Acclimatisation Societies. It was his duty to show the relationship between the anglers and the committee. The Research Committee was responsible only to the association, and need have no direct relation with the various societies. When the committee was set- up it was decided that the delegates should ask their societies to give 40 per cent, of their opossum revenue and 10 per cent, of their fishing revenue towards the costs of the work of the committee. He detailed how financial troubles had been overcome. At the time when the committee was set up, he said, there had been a great outcry about the diminishing size of the fish which were being caught. The committee had been asked to investigate the Oreii River, which, despite efforts at re-stocking, was yielding smaller and smaller fish. The upshot of that investigation was the discovery that the weight of the fish in the Oreti had been, diminishing from as far back as it had been possible to go. Among other things it had been discovered that there had been a vast increase in the licenses sold, and he had been led to believe that tho increase in the number of motor cars in use had caused the intensity of angling to increase enormously. He went on to speak of the habits of the fish as rfevealed by his researches on the Oreti. The increase in speed of travel arid the greater accessibility to the trout streams had resulted in a greater death rate in fish, and! this had been found to apply throughout the country.

The problem of the societies, then, was how to prevent the decrease in weight. The theory had been put forward that the trout had changed and had become migratory and 1 the reason given was the extent of whitebait fishing carried oiii. There was evidence, however, that trout had been migratory ever since they had been introduced. He was quite certain on the evidence available that the brown trout had not changed its habits. This reminded) him of one of Otjigo’s problems—.the Waikonaiti. For years and years the society had been putting fish into that stream, and they always disappeared. There was no evidence that they died on the spot, so they must go aivay. Going on to the subject of food, Professor Percival said it was contended that certain insects had decreased. Unfortunately, no' attempt to count these insects had been made before 1929. He explained how estimates of the numbers of insects were arrived at, and said that it was not possible to say whether a stream was well populated by them'or not. As nothing of this sort had been done beioro the fisli were introduced, it was not possible to say w T hat effect trout had had on the insect life. Generally it was found that the biggest fish| were in the rivers which were strong running, and the smaller fish were more plentiful in the slower streams which were equipped with more food supplies. Professor Percival explained the differences he had fundi in feed conditions between a stream] which had never been stocked and one which had. The results of this investigation, howeyer, lie said, were not conclusive.

He Aveni on to say that if fisli A\ T ere continuously put into a river at the head, they had to look for more room and eventually reached tho sea. A fiver could hold only so many fisli, and the surplus had to go away. This sort of thing had) to he kept in mind in investigating the problems tackled by the committee.

An examination of the growth rate of trout had been an important* part of the committee’s Avork, said Professor Percival. He dealt with the field Avork AA r hicb had been done in this connection, and stated that a mass of information was now being put on record and this would be available for future comparisons. It might appear, he said, that much of this had little relation to the taking of fish on the end of a line, but it was necessary to realise that a great deal of information Avas necessary on which to have practical calculations. The questions AA'hen fish Avere in the best condition and Avhat factors contributed to the best groAvth Avere fully dealt Avith by the speaker, Avho Avent on to explain Avhat had been done in connection Avith the recurring problem ol ‘‘starving” fisli. It had l been found, he said, that, Avithin certain limits, tho appetite of the trout was affected by changes in temperature. This Avas important in connection with the study of groAvth. One point Avhich had arisen out of the examination of scales Avas the determination of the age at which fish became mature. The speaker elahoiated on the question and referred to its significance in the determination of the minimum takeable size. In 1932 investigations 1 of the mortality of naturally spawned eggs had been commenced and the field Avork had been carried on for two years. It had been said that the arrival of the quinnat salmon in. certain Canterbury rivers had resulted m the ruination of the trout. The investigator had examined a large piece of country including places whose rainfall varied! from 35 inches to over 200 inches per year. All types of streams had been included in the examination, and about 200,000 eggs had come under his notice. Processor Percival summarised the eonelusions Avlxich could bo reached as a result of this work and explained that the information could not yet he put to practical use.