An on-farm experiment was undertaken in nine earthen ponds to evaluate the growth and production potentials of stinging catfish shing, Heteropneustes fossilis for the period of six months from March to August 2010. Three stocking densities such as 1,25,000 (T1), 1,87,500 (T2) and 2,50,000 ha-1 (T3) were tested with three replications each. Fish were fed with commercial pelleted feed containing 35% crude protein. After six months rearing, the mean harvesting weights of shing were 69.42±6.20, 58.74±3.85 and 49.50±4.52g in T1, T2 and T3, respectively. Significant (P<0.05) highest mean harvesting weight was found in T1. The best survival was found in T1 (87%) among the treatments. The calculated mean production of shing (H. fossilis) in three treatments such as T1, T2 and T3 were 7549±52, 9031±71 and 8786±60 kg ha-1, respectively, which were significantly different (p<0.05) from each other. DOI: http://dx.doi.org/10.3329/ijarit.v2i2.14009 Int. J. Agril. Res. Innov. & Tech. 2 (2): 9-14 December, 2012

The fingerling‐rearing experiment of the threatened catfish, Mystus cavasius was carried out at different stocking densities in earthen nursery ponds. Twelve‐day‐old fry were stocked at 200 000 ha−1 in treatment‐1 (T1), 250 000 ha−1 in treatment‐2 (T2) and 300 000 ha−1 in treatment‐3 (T3) respectively. The mean length and weight of fry at stocking was 1.24 ± 0.25 cm and 0.11 ± 0.04 g respectively. Fry in all the experimental ponds were supplemented with SABINCO nursery feed for the first 14 days and starter‐I feed for days 15–56. The physico‐chemical parameters and plankton population of pond water were within the suitable level for fish culture. Growth in terms of final weight, final length, weight gain, length gain and specific growth rate and survival of fingerlings were significantly higher in T1 than those in T2 and T3. Feed conversion rate was significantly lower in T1 followed by T2 and T3 in that order. Significantly higher number of fingerlings was produced in T3 than that in T2 and T1. Even then, consistently higher net benefits were obtained from T1 than those from T3 and T2. Among the treatments evaluated, 200 000 fry ha−1 was the best stocking density considering the highest growth, production and net benefits of fingerlings of M. cavasius in nursery ponds.

Molluscs are the most important resources among all the seafood items in South-East Asian countries. However, very little information available on nutritional value of molluscs in these regions. In this study, we evaluated the 7 economically important species of molluscs in terms of proximate composition, amino acids profile, fatty acids profile, cholesterol and heavy metal contents in the bivalves (mussels, oysters, clams and cockles) and univalve (snail) collected from freshwater and marine environments of Bangladesh. The results of the proximate analyses revealed that significantly higher amount of crude protein contents were present in marine water oysters, clams and cockles (59.3 AE 0.3 to 75.4 AE 0.2%) than the freshwater mussels and snail (36.9 AE 0.4 to 49.6 AE 0.6%) on dry matter basis. However, carbohydrate contents were significantly higher in freshwater mussels and snail (30.2 AE 0.9 to 57.3 AE 0.2%) compared to the marine water bivalves (8.1 AE 0.4 to 20.2 AE 0.6%). Crude lipid contents were ranged from 2.5 AE 0.2 to 11.2 AE 0.1% and ash from 11.4 AE 0.1 to 16.8 AE 0.6% among the bivalves and snail species. The amino acid contents were comparatively higher in marine water bivalves than their freshwater counterparts. Saturated fatty acid contents were found to be higher in marine water bivalves than the freshwater mollusc species. The results also show that the omega-3 (eicosapentaenoic acid, EPA and docosahexaenoic acid, DHA) fatty acids were comparatively higher in oysters, clams and cockles in marine water than those in freshwater mussels and snail. However, omega-6 fatty acids like linoleic acid (LA), αlinolenic acid (ALA) and arachidonic acid (ARA) were higher in freshwater mussels and snail than in the marine bivalves. The n-3/n-6 ratio were significantly higher in oysters and cockle species than the other groups of bivalves and snail. The index of atherogenicity and index of thrombogenicity of the mollusc species ranged from 0.74 AE 0.1 to 1.74 AE 0.2 and 0.5 AE 0.1 to 2.6 AE 0.2, respectively. The results show that marine water bivalves contained higher amount of potassium, sodium, iron, chlorine especially oyster species contained significantly higher iodine than the freshwater bivalves and snail. However, freshwater mussels and snail showed significantly higher amount of zinc contents than the marine bivalves. The heavy metal contents such as arsenic, chromium and mercury were absent or present in very tiny amounts among the mollusc species. Significantly higher amount of cholesterol was present in marine bivalves and freshwater snail species than the freshwater mussels. Overall, the results indicate that marine bivalves can be good sources of high quality protein and lipid especially EPA and DHA. On the other hand, freshwater mussels and snails also could be good sources of protein, LA and ARA but scarcity of EPA and DHA.

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