The state of Haryana in northeastern India has an excellent sub-tropical climate for the development of fresh water fish culture in a variety of aquatic bodies. Aquaculture not only plays an important role in nutrition but also in the rural economy of the State. The main purpose of the present study was to identify the primary production and fish production patterns in village ponds under different management practices. With a more or less narrow range of primary production, varying fish production and growth rates were recorded, indicating the influence of a combination of environmental and management factors. There was no close relation between primary production and fish production in the rural fish ponds of Haryana, India. Sudden and considerable fluctuations in dissolved oxygen concentration and pH impair the proper functioning of other trophic communities, supported the dominance of decomposition processes, i.e., anaerobiosis, and lead to further degradation and loss of the control functions of the whole water ecosystem. Increased organic load can be considered as a general signal of reaching the instability of aquatic ecosystem and decrease of production efficiency The optimum conditions for increased fish productivity were found to be the adequate DO level (>4 mg L -1 ) and appropriate pH (6 < pH < 9), low BOD (<1.6 mg L ).

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Two experiments were conducted to investigate the effect of inland water salinity on growth performance, feed conversion efficiency and intestinal enzyme activity in grey mullet. In experiment I, a 90 day monoculture of grey mullet at different salinity levels (0, 10, 15, 20 and 25&) was carried out. The fingerlings were stocked at 5000 per hectare and fed on a supplementary diet at 5% BW d À1 . This Study revealed that fish growth mean body weight (90.5 ± 4.5 g) and mean length (21.6 ± 0.4 cm), SGR (4.70%) and growth per day (0.99 g d À1 ) were significantly (p < 0.05) enhanced in fish maintained at 10& salinity in comparison with other treatments. Nutrient levels, phytoplankton population, NPP and chlorophyll 'a' all decreased with an increase in salinity (>10&). In addition, zooplankton populations increased with an increase in the salinity level. Most of the other hydrochemical characteristics remained at optimal levels in all other treatments. Fish weight gain showed a significant positive correlation with productivity indicating parameters viz. alkalinity (r = 0.53), turbidity (r = 0.62), NPP (r = 0.75) and chlorophyll 'a' (r = 0.46), clearly revealing that fish growth is also related to the trophic status of the ponds. In the second experiment (Experiment II), mullet fry were exposed to five different salinity levels (10, 15, 20, 25 and 30&) and maintained for 70 days in the laboratory. Significantly (p < 0.05) high growth, (SGR and per cent increase in body weight), feed conversion efficiency and intestinal enzyme activity were observed in the group maintained at 10& salinity in comparison with other groups maintained at similar salinity levels. Carcass composition, musc1e and liver glycogen levels were also significantly (p < 0.05) affected by salinity changes.

Studies were conducted to evaluate the antimicrobial potency of skin mucus collected from three carp species; Hypophthalmichthys nobilis, Ctenopharyngodon idella, and Cyprinus carpio (exotic to India) against certain human and fish pathogenic bacterial strains viz. Klebsiella pneumoniae, Pseudomonas aeruginosa, Escherichia coli, Staphylococcus epidermidis, Staphylococcus aureus, Bacillus cereus, and Aeromonas hydrophila. The antimicrobial activities were measured in terms of zone of inhibition (ZOI) in mm and compared with two antibiotics (amikacin and chloramphenicol). All selected fish species were also challenged with A. hydrophila through water to check, if there is any change in mucus secretion or its antibacterial effects. Studies have shown that after challenge with A. hydrophila, an increase in mucus secretion was observed in all the three species of carps. Skin mucus extracts (crude and aqueous) obtained from healthy and challenged fish species exhibited strong antibacterial activity against all the investigated microbial strains. Variations in antibacterial effect have been observed among same fish (in healthy and challenged) and amidst different carp species against same and different bacterial strains. In general, crude mucus of all the fish species showed higher bactericidal action than its aqueous extracts and antibiotic chloramphenicol. Hence, these results have clearly revealed that the mucus obtained from fish skin shows antibacterial activity which may play an important role in fish protection against pathogens and thus there appears to be a possibility of using mucus obtained from the skin of carps as an alternative to antibiotics in animals and possibly also in human health related problems.

The effects of four different doses of organic (cowdung) and inorganic fertilizers (single super phosphate: SSP) in combination were studied on plankton production, species diversity and fish biomass in saline and freshwater fish ponds. Physico-chemical factors of pond waters were also monitored.