FT Vol.58(3)

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    Efficacy of a Closed Water Depuration System with Charcoal filter on the Bacteriological quality of Villorita cyprinoides var. cochinensis (Hanley, 1866)
    (Society of Fisheries Technologists (India)Cochin, 2021) Antony, Ally C.; Silvester, Reshma; Aneesa, P. A; Francis, Bini; Abdulla, Mohamed Hatha
    Bivalves are good bio-indicators of the sanitary quality of the aquatic bodies in which they survive. The sanitary quality of the shellfish harvesting areas is assessed based on the faecal coliforms/E. coli levels of the harvesting water/shellfish tissue; on exceeding the regulatory limits depuration suggested. In the present study, the efficacy of a closed water depuration system attached with a charcoal filter to depurate Indian black clams (Villorita cyprinoides var. cochinensis (Hanley, 1866) was evaluated. The depuration system consisted of a closed water holding glass tank, with a wall-hung immersion water pump which re-circulated (18 l min-1) the seawater [salinity – 10 ppt, pH -7.3, ambient temperature (29-30°C)] through a coconut shell based activated carbon (charcoal) filter. Clams were sampled at time intervals of 0, 6, 12, 24, 72, and 96 h to assess the reduction of total coliforms (TC), faecal coliforms (FC) and faecal streptococci (FS). Initial TC, FC, FS and Salmonella loads were assessed using standard microbiological methods. Salmonella was not detected in any of the clam samples. Complete removal of both FC and FS whose initial loads were 4.6 x 104 MPN 100 g-1 and 1.1 × 105 MPN 100 g-1 respectively was observed within 48 h. Maximum rate of depuration of TC, FC as well as FS were observed during the initial first 6 h. However, TC could not be fully depurated even after 96 h of depuration. The differences in the depuration rates of TC, FC and FS were found to be statisticallysignificant (p<0.05). The FC load of the black clams selected for the study conformed only to the class C shellfish growing area of EU which could be reduced to acceptable regulatory limits of <230MPN 100 g-1 of depurated shellfish; which proved the system used is efficient. The system uses simple, cost-effective, easily available, natural, and renewable water treating agent such as coconut shellbased activated carbon and is suitable for household purposes. In India, black clams do not have much export value and is also not preferred to be eaten raw. Hence less stringent, cost-effective, and simple depuration measures as mentioned above may be sufficient enough to meet the required sanitary quality as it is consumed only after proper cooking.
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    Economics and Resource use Efficiency of small scale Fish Production in Manipur
    (Society of Fisheries Technologists (India)Cochin, 2021) Singh, Kh. Rishikanta; Ch. Basudha, Ch. Basudha
    The present study was taken up in Manipur state of north east hill region to examine the economics and resource use efficiency in fish production. Three districts viz., Bishempur, Imphal West and Thoubal were selected for the study and two villages were selected from each district. From each villages 25 fish farmers were randomly selected, altogether there were 150 respondents. The farmers were classified into marginal, small and semi-medium category based on pond size. Cobb-Douglas production function and marginal value productivity were employed to examine the resource use efficiency. Per hectare cost of fish rearing were the highest for the marginal category and decrease with increase in pond size category. The overall average yield of fish was 1078 kg ha-1. Farmers in the marginal category obtained the highest yield with a production of 1611 kg ha-1. The yield decrease with the increase in pond size. Net return obtained from fish production were Rs.125311 ha-1 for marginal, Rs. 87010 ha-1 for small and Rs. 29471 ha-1 for semi medium category respectively. Fish production is profitable with a BC ratio of 1.60 but the productivity is very low and needs to be increased. It was found that fish seedling was underutilized for semi-medium category, feed was underutilized for marginal category and labour was underutilized for both small and semi-medium category farms. Floods, poor quality of pond water, incidence of pest and disease, high cost of feed and lack of skilled workers are five major problems faced by the fish farmers