342
CALCIUM CONTENT OF SOME FISHERY WATERS [ Vol. XXV, Part IV,
and again with 1210 fingerlings of the same species on the 13th January, 1950.
Netting was started from the 17th June 1950 and continued till 17th July, 1951.
The fish yield from this tank in two years (1949 to 1951) was 31 maunds, 12 seers
and 12 chataks (1278 lb. per year per acre) yielding a revenue of Rs. 1,085-10-6.
According to Ganapati and Chacko [1950] a ' very good ' tank yields about 2000 lb.
of fish per year per acre and for really ' good production ' about 650 p.p.m. of calcium
as carbonate is essential [Chacko and Ganapati, 1949].
Turki tank, Lucknow, with an area of about two acres did not have such good
growth as was the case with Garha tank and the values for calcium (CaCO 3 ) in this
tank ranged between 21 and 135 p.p.m. In this tank also, the calcium values
were high during summer, otherwise they ranged between 20 and 30 p.p.m. From
this it appears that calcium content varies with the depth of water in ponds. Turki
tank was stocked on 4th February, 1950, with 1200 fingerlings of Rohu, Nain
and Catla. The fish yield from this tank was only eight maunds in one year and
10 months from Feburary 1950 to November 1951 (357.8 lb. per acre per year).
The hydrobiological conditions prevailing in these two tanks are given in Appendix
II and the chemical constituents of the bottom soil are given in Appendix III.
The work on the growth of fish in tanks enriched by adding slaked lime is under
progress and will be published later.
CONCLUSIONS
In the samples of waters analysed calcium as carbonate ranged between 14 and
256.5 p.p.m. The values of calcium were high during summer due to appreciable
reduction in the depth of water. Of the water samples, 9.2 per cent were poor,
32.9 per cent were good and 57.9 per cent were very good, when classified according
to calcium contents.
ACKNOWLEDGMENT
Thanks are due to Dr A. J. Faruqi, Lucknow, Sarvshri K. H. Alikunhi, Cuttack,
and P. I. Chacko, Calicut, for valuable suggestions during the preparation of this
paper. Plankton data were supplied by Shri R. N. Misra, Technical Assistant,
to whom the author is also thankful. Thanks are also due to Dr R. L. Kaura,
Director of Animal Husbandry, Uttar Pradesh, for granting permission to publish
the paper.
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