FRESH WATER RESEARCH

Southland Times, Issue 22013, 12 May 1933, Page 9

FRESH WATER RESEARCH

COMMITTEE’S ANNUAL REPORT. VALUABLE DATA GATHERED. The Research Committee of the Southland Acclimatization Society in its annual report states:— It was decided that the greater part of the off-season’s work should be concentrated on the Aparima River so far as tagging and sampling was concerned. This decision was reached as it was considered that in the light of our previous experience with the Oreti a more regular programme could be carried out on the Aparima, and because it was felt that new data would be furnished differing from what had been gathered from the Oreti. Fish have been tagged at various places between Etal Creek and Thornbury, 141 large tags and 158 small tags, making a total of 299, have been used in marking. As small tags were unobtainable, tagging was restricted, and an additional 228 scale samples were taken. This makes a total of 527 scale samples forwarded to Christchurch for the winter’s work All but 10 of these were from the Aparima. The rivers were up in June but one visit was paid to Fairfax when, owing to an accident to the gear, no fish were taken. The absence of small tags was a severe handicap and in response to urgent requests for a further supply the Central Committee informed us that owing to the high cost and gloomy outlook no more were being imported at present. However, Professor Percival, in his letters to Mr Jacquiery, urged that we should continue taking samples through the winter as these would yield results which were not to be had from trapped fish which are usually large spawning specimens, and further that ours was the only society carrying out this particular method of scale sampling. A notable recapture of tagged fish was made at Thombury when three fish which had been tagged eleven months previously were retaken in the same pool where liberated. This tends to show that they had not yet become migratory and though the growth was rather poor the scales were of considerable importance in checking trie empirical methods used in scale reading. The particulars are as follows: — Tag 891—Length 14Jin; weight lib; gained length 2iin; weight 9oz. Tag 892—Length 15in; weight 11b 3jt oz.; gained length 2in; weight IJoz. Tag 898—Length 13Jin; weight 13Joz; gained length IJin.; weight s}oz. An inspection of the tagging results show that the fish on the average were larger in the lower reaches of the river. A special trip was made to Mossbum to Mr F. Christie’s farm to see if the average fish there were larger than lower down the Oreti. This was our least pleasant experience. The day was cold and fairly heavy rain set in. The river was swift and difficult to work. Mr Christie piloted the party, all the members of which got thoroughly wet. It soon became impossible to make records, but eight large fish were tagged and two samples taken from small fish. Our thanks are due to Mrs Christie for a hot meal and drying clothes. In view of the opinion generally held by anglers that these big Mossbum fish stay in the pools all the year it may be interesting to note that Mr Parrott, from/ scale readings of a Mossburn tagged fish caught later, is of opinion that it migrated at the end of the first year and had spawned in the third, fourth, fifth and sixth winters. A keen angler in Mossbum said that he had seen the big fish coming up in shoals to spawn. Some anglers have complained that as a result of tagging fish become slabby. We have insufficient records of recaptures to make a positive statement, so a request was made to Mr Parrott to state what his records showed. Mr Parrott said that the records did not show any preponderance of slabs among the tagged fish, and tagging has no ill effect. It may be as well to point out here that the nervous system of a fish is quite different from that of the higher vertebrates, and the injuries caused by a tag would not be felt or affect a fish as it would a mammal. It is stated that several anglers who have caught tagged fish failed to send in particulars and scales and this is to be regretted in view of the amount of time and expense involved and that the work is being done for the benefit of anglers generally. Other anglers have given particulars of growth, but omitted to send scales. We wish to impress on anglers that the scales are of prime importance. Even if the angler sends scales without length and weight these latter may be found by scale measurement, though they may differ slightly from the actual length and weight.

Professor Percival has made an attempt to get the hatchery costs of the Dominion brought together and to this end particulars of our costs were forwarded through our secretary. Observations have been made on the rate of flow of rivers, the condition of the bottoms, whether stable or otherwise, size of gravel, and flora growing m the water. One result of the work in the Aparima has been to bring to hght the fact that a large proportion of the fish up to 12 inches have apparently not spawned, being immature. To confirm the results of hundreds of inspections made, a small number of immature fish were killed and the internal organs examined, leaving no doubt of the truth of our assumption. Another thing noted was a very great preponderance of female fish. Professor Percival has stated that this investigation was of the first importance. As many anglers contend that trout in other streams commonly spawn at 9in., but are unable to give any exact figures to support itieir statements, the committee intends to test some of the streams indicated, such as the Otapiri, etc.

The size at which trout spawn , has a direct bearing on the . size limit It will, we think, be admitted that it is advisable for a fish to spawn once to help keep up the stock and reduce hatchery expenses. In this matter exact information is necessary for our own guidance. Professor Percival in a letter to Mr Jacquiery says that “the smallest fish to give spawn that he had seen this year in the main drairr was 12| inches.” He had counted the eggs of a number of fish and that there was a tendency for small fish to Produce small eggs, and owing to the smaller yolk these may produce small fry. He thinks that 12in. might well be the minimum size. The problem is to raise the size of the fish in. the early part of the season and only by size and long limits can this be got quickly. . . Mr Parrott paid a visit to this district in December last. He was met by the president and Mr Jacquiery and an evening was spent in discussing research problems, scale reading, etc., and many obscure points were cleared up. Mr Parrott visited the Oreti where scale samples had been taken, to check up some of the data by personal inspection, and was well satisfied with the result. Mr Jacquiery has during the summer been making some investigations into whitebait spawning grounds, and with the President and Mr Hefford made an inspection of the lower Mataura, where a commercial fishery exists. As it would seem that lack of safe spawning grounds is a considerable factor in the diminution of whitebait, we should afford the Marine Department help towards establishing some protection to this delicate food fish. „ We have to thank Mr F. M. Corkill, through whose courtesy our secretary was enabled to visit the Otapiri and ■make a scale collection and an examinlation of the organs of twenty fish. Mr

J. D. Speirs also supplied a collection of 30 sets of Waiau scales on which a special report was obtained, the average age being 2.6 years and average length. It would appear that the average fish in the Waiau is better than in the Oreti. The BJlb male salmon, 4j years old, forwarded by Mr Speirs from the Waiau at Wairaki, had spent one year prior to migration, the presmolt growth being small (3.9); the next year it grew to 20.1 inches, which is above the average. Mr Parrott says . that the growth rings on scale differ from others he has examined, not being typical lake growth; it had spawned in the second and fourth winters, but he would not say it was a sea-run fish without further material from the mouth of the Waiau. The chairman supplied three sets of Rainbow scales from Lake T 1 omas which showed extremely slow growth. No. 2,18 in long, was the smallest six-year-old fish Mr Parrott had examined. The thanks of the committee are due to Messrs F. Henderson, F. Strang, W. Henderson and J. D. Spiers for transporting parties to the rivers; also to Messis G. Braxton, B. Challis and H. R. Cottrell for complete fishing diaries. Many of those who undertook to keep diaries have not returned them. Ouy thanks are also due to 'those who returned tags and supplied particulars of fish, and those anglers who forwarded scale samples. Valuable reports from the Central Committee have, through the courtesy of the Press, been made available for anglers generally.