Fluctuations in mackerel landings at Calicut in relation to hydrographical factors

Of the hydrographical factors, temperature and salinity have been found to exert a profound influence on the fish throughout its life-cycle. The tolerance range of the hydrographical factors of fishes is characteristic of the species. Even within the same species, the degree of tolerance may vary slightly, depending upon the age of fish; the degree of tolerance, however, increases with the growth of fish. Chidambaram (1950), has shown that sardine catches are maximum when the hydrographical factors are within certain limits, during the season. Pradhan (1956) remarks that the entire stock of mackerel, impounded near the mouth of Kali River is apt to die from a sudden fall in salinity, due to the influx of freshwater from the river. Similar observations were made by Hubbs (1948), Jenson (1930), Radovich (1961), Tanoue and Enami (1954), Tonoue (1958 and 1960) and Walford (1946). Hubbs {loc. cit.) showed that seasonal migrations of fish of the west coast of United States are controlled by temperature

Seasonal variations of the hydrological factors of the madras coastal waters

Studies on the hydrological conditions in the coastal waters of India are few compared to similar investigations in the temperate zones. It is an accepted fact that the chemical constituents, especially the nutrient salts, present in the waters act as limiting factors in the distribution and abundance of plankton, which is an important link in the food chain of fishes. Therefore the importance of hydrological studies in a fisheries research programme needs no emphasis. The present paper, embodying the results of investigations carried out at Madras from June 1956 to May 1958, deals with the seasonal fluctuations of pH, salinity, dissolved oxygen, phosphates, silicates and nitrites

Primary production of an atoll in the Laccadives

According to YONGE (1960) "an atoll raised to the surface in the midst of oceanic waters may be described as a large scale experiment in nature". Earlier studies have contributed to an understanding of primary production of atolls and coral reefs of the Pacific and Atlantic Oceans (SARGENTan d AUSTIN, 1949, 1954; ODUMa nd ODUM1, 955; KOHNa nd HELBRICH1, 957; ODUMB, URKHOLDER and RIVERO1, 959 ; GORDOaNn d KELLY1, 962). Comparable information on the atolls of the Indian Ocean has been completely lacking. Since GARDINER (1903-1906) published his classical work on the Maldive and Laccadive Archipelagoes, practically no knowledge has been added to the atolls of the Laccadive

Genetics, genomics and breeding of groundnut (Arachis hypogaea L.)

Groundnut is an important food and oil crop in the semiarid tropics, contributing to household food consumption and cash income. In Asia and Africa, yields are low attributed to various production constraints. This review paper highlights advances in genetics, genomics and breeding to improve the productivity of groundnut. Genetic studies concerning inheritance, genetic variability and heritability, combining ability and trait correlations have provided a better understanding of the crop's genetics to develop appropriate breeding strategies for target traits. Several improved lines and sources of variability have been identified or developed for various economically important traits through conventional breeding. Significant advances have also been made in groundnut genomics including genome sequencing, marker development and genetic and trait mapping. These advances have led to a better understanding of the groundnut genome, discovery of genes/variants for traits of interest and integration of marker‐assisted breeding for selected traits. The integration of genomic tools into the breeding process accompanied with increased precision of yield trialing and phenotyping will increase the efficiency and enhance the genetic gain for release of improved groundnut varieties

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Not AvailableOf the hydrographical factors, temperature and salinity have been found to exert a profound influence on the fish throughout its life-cycle. The tolerance range of the hydrographical factors of fishes is characteristic of the species. Even within the same species, the degree of tolerance may vary slightly, depending upon the age of fish; the degree of tolerance, however, increases with the growth of fish. Chidambaram (1950), has shown that sardine catches are maximum when the hydrographical factors are within certain limits, during the season. Pradhan (1956) remarks that the entire stock of mackerel, impounded near the mouth of Kali River is apt to die from a sudden fall in salinity, due to the influx of freshwater from the river. Similar observations were made by Hubbs (1948), Jenson (1930), Radovich (1961), Tanoue and Enami (1954), Tonoue (1958 and 1960) and Walford (1946). Hubbs (loc. cit.) showed that seasonal migrations of fish of the west coast of United States are controlled by temperature.Not Availabl

Not Available

Not AvailableStudies on the hydrological conditions in the coastal waters of India are few compared to similar investigations in the temperate zones. It is an accepted fact that the chemical constituents, especially the nutrient salts, present in the waters act as limiting factors in the distribution and abundance of plankton, which is an important link in the food chain of fishes. Therefore the importance of hydrological studies in a fisheries research programme needs no emphasis. The present paper, embodying the results of investigations carried out at Madras from June 1956 to May 1958, deals with the seasonal fluctuations of pH, salinity, dissolved oxygen, phosphates, silicates and nitrites.Not Availabl

Denitrification in the Arabian Sea

Estimates of the amount of denitrification in the Arabian Sea are inconsistent, and so two methods of calculation of 'original' nitrate concentrations used in earlier studies have been reviewed. Nitrite at intermediate depths was not restricted to the Persian Gulf water; concentrations were maximal much shallower than the depths of the Persian Gulf water. The nitrate-salinity relationship used to calculate 'original' nitrate concentrations in a recent study would lead to an underestimate of nitrate deficits because the approach requires denitrification to be restricted to Persian Gulf water. A method involving oxidative ratios has been modified and used to calculate nitrate deficits. The deficits so calculated lie between the values reported earlier. The degree of denitrification decreases steadily southward. The results indicate that denitrification extends up to 11 or 12°N latitude. Taking 30 years as the average residence time of water for the layer in which denitrification occurs, the denitrification rate in the Arabian Sea has been calculated as about 3.2 × 1012 gy-1. This represents about 5% of the annual global denitrification

Not Available

Not AvailableAccording to YONGE (1960) "an atoll raised to the surface in the midst of oceanic waters may be described as a large scale experiment in nature". Earlier studies have contributed to an understanding of primary production of atolls and coral reefs of the Pacific and Atlantic Oceans (SARGENTan d AUSTIN, 1949, 1954; ODUMa nd ODUM1, 955; KOHNa nd HELBRICH1, 957; ODUMB, URKHOLDER and RIVERO1, 959 ; GORDOaNn d KELLY1, 962). Comparable information on the atolls of the Indian Ocean has been completely lacking. Since GARDINER (1903-1906) published his classical work on the Maldive and Laccadive Archipelagoes, practically no knowledge has been added to the atolls of the LaccadivesNot Availabl