BIOLOGIST’S RESEARCH WORK

Evening Star, Issue 22453, 25 September 1936, Page 14

BIOLOGIST’S RESEARCH WORK

SPAWNING REDDS IN KAKANUI INTERESTING RESULTS OBTAINED [From Our Correspondent.] Mr D. F. Hobbs, biologist to tbe Freshwater Research Committee, who for the past fortnight has been investigating the spawning redds in the Kakanui River, gave an interesting and instructive account of the results of his research work to the members at the annual meeting of the North Otago Angling Club. Mr Hobbs has examined the river bed from the Kakanui traffic bridge to Five Forks, and also the Kauru River, and from his investigations it would appear that in this stretch of the river there are half a million fertile ova in the spawning redds. Mr Hobbs said the two problems facing the Research Committee were the number of fish and the size, and they were trying to find out the relative importance of hatchery output and natural production. The bulk of the money of societies vas spent on stocking rivers through hatcheries - on the assumption that there was a great loss on natural production. His research work had started at Avoca, and after examining over 200,000 specimens he found thev were pretty clean throughout and virtually all the eggs were fertilised at spawning time, the loss being less than 2 per cent. The testing of the redds showed that the eggs gob a fair start in life, except for muddy localities where they were smothered by the mud. The fish laid the eggs in a substantial type of shingle bed in the Kakanui, but there was the natural small loss and loss from flood action, and from superimposition of the redds from fish spawning later than the early ones. The Kakanui River bed was very suitable for spawning redds, but when the river was low and unsuitable for the fish to go over the dam the fish came up later on and super-imposed the eggs on the earlier redds, and some of the earlier eggs were lost through being dislodged by the later fish. Mr Hobbs recounted bis experiences in the examination of the redds from the mouth of the river to Ruddenklan’s in the hills. He bad counted all the redds, and dug every twentieth redd, and in that way they got a fair sample. Ho found the average number of eggs in every twentieth redd, and multiplied the number by 20, and arrived at a very conservative total, as a considerable number of eggs would be missed in the netting and missed in the examination.. There were 364 redds discovered, and the result was approximately 534,400 _ eggs. Of the 40,000 specimens examined, 1,800 were dead, which represented a loss of 2 per cent. Out of the total, 162,000 eggs were in the mill race, which was found to be a valuable spawning area of the river, and if the whole race could be made suitable for spawning there would be a million eggs there, which would make the work of taking shingle to the race well worth while. The river did not have sufficient spawning areas for the number of fish wanting to spawn, as the late fish disturbed the early spawning. The improvement of the spawning area in tho race was one of the possibilities that , was shown through the research work, and such improvement there would not affect the spawning areas upstream, which were approaching capacity. Mr Hobbs_ answered several questions on tho subject, and was accorded a very hearty vote of thanks for his address.,