• N K Panikkar

      Articles written in Proceedings – Section B

    • Some aspects of adaptation inChanos Chanos (Forskål)

      N K Panikkar P R S Tampi R Viswanathan

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      A study has been made of the adaptive responses ofChanos to variations in external salinity and temperature. In external salinities varying from 0·l% NaCl (hard tap water) to 5·3% NaCl (sea-waterplus common salt),Chanos fingeriings retain their blood serum chloride values fairly constant over a narrow range of 0·3% NaCl. In dilutions of tap water corresponding to a chloride content of 5 p.p.m. and less, the serum chloride values suggest a breakdown of the osmoregulatory mechanism.

      The period of survival ofChanos fingeriings in glass-distilled water is prolonged if they have been preacclimatised to fresh-water or if sodium or calcium chloride has been added to the medium. The serum chloride values for fingeriings kept in solutions of calcium chloride (144 p.p.m. of Ca) indicate that calcium in the external medium aids the fish in the retention of blood salts.

      The chloride and calcium contents of natural fresh-waters appear to be of critical significance whenChanos is transferred direct from high salinities. The heat death temperatures ofChanos fry and fingeriings (43 and 39° C. respectively) are higher than those reported for marine fishes. The heat death temperature of the fry is not significantly influenced by the salinity of the medium, the per cent, survival of the fry at any temperature being dependent only on the temperature of the water and the time of exposure.

      The fry and fingeriings are able to withstand momentary exposures to 18° C. and 14° C. respectively, both in sea-water and in tap water.

    • Biological and oceanographic differences between the arabian sea and the bay of bengal as observed from the Indian region

      N K Panikkar R Jayaraman

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      The paper presents some of the important differences in the oceanographical and biological conditions in the waters of the Arabian Sea and the Bay of Bengal along the Indian coasts. In discussing the biological variability of the two environments from the point of view of fishery productivity, attention is particularly drawn to the extremely complex nature of the oil sardine and mackerel fisheries, especially along the west coast of India, which accounts for the bulk of the fish landings. An attempt is being made to provide a suitable explanation for this on the basis of the nutrient distribution pattern associated with the occurrence of seasonal ‘upwelling’. It is also pointed out that the ‘upwelling’ processes along the west coast of India are also of a complex nature and the forces leading to this are yet to be properly understood. Some comparison is drawn between the conditions on the south-west coast of India and some of the classical upwelling regions of the world, particularly with reference to two important features, namely, formation and disappearance of temporary banks of mud and the occurrence of special planktonic blooms often leading to mass mortality of fish.

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