FRESHWATER FISH RESEARCH

Press, Volume LXX, Issue 21243, 15 August 1934, Page 4

FRESHWATER FISH RESEARCH

BLUE SWELLING IN TROUT DISCLOSURES FROM SCALE READING The New Zealand Freshwater Research Committee met yesterday. Present were Messrs A. E. Hefford (chairman), Dr. G. F. V. Anson, Messrs M. H. Godby, E. J. C. Wiffen, G. Howes, Professor E. Percival (director of research), Messrs D. F. Hobbs (secre-! tary), and A. W. Parrott (biologist). Professor Percival reported that experiments were being carried out to determine the effect of lime on blue swelling. The experiments were incomplete, but results so far indicated that lime reduced the incidence of the disease. In his report, on the work of the committee, Professor Percival said that the survey of size and growth of trout was proceeding, and several interesting points that had arisen were followed up. One point was the significance of the relation between condition of trout, the time of the year, and state of scale growth. Another was the study of the nature of the first eirculi laid down in hatchery and wild fish which might throw light on the efficiency of artificial stocking with fry. A report had been made on the Oreti river system. Work on the early life of trout was being continued in Westland, where spawning runs were being studied intensively. A table showing the age-distribution of fish in the Waikato river and two of its tributaries, the Waipa and the Pokaewhenua was included in Mr Parrott's report. The fish from the main river showed a wider and more even age-distribution. This was also found to be the case in other river systems examined. The report recommended that minimum sizes of 12 inches for the two tributaries and 12J inches for the Waikato be adopted. It was found from an analysis of material from the Rangitata that there was a fairly close correlation between winter band formation and the condition of the fish. A rise in the temperature of the water in spring and early summer was associated with an increase in the growth in length of the fish. Mr Hobbs was asked to prepare a summary of his work in the field for the conference of acclimatisation societies.