Two experiments were conducted with a view to assessing the effects of stocking densities on the growth and breeding performance and larval growth and survival of Channa striatus. The first one was carried out with a view to find a suitable stocking density of Channa striatus at which they could spawn while the second experiment dealt with the effect of stocking density on growth and survival of the produced larvae. The first experiment was carried out in nine equal-sized chambers of raceway separated by netted wooden frame with an area of 1.83 ×1.12m 2 each. The effective water depth in each of the raceway chambers was maintained at 1.2m. The broodfish were stocked at 4 (357.22g/m 2 ), 6 (541.78g/m 2 ) and 8 (719.18g/m 2 ) at 1:1 male-female ratio and fed with washed and chopped poultry viscera twice a day and with live silver carp fry twice a week. No significant (P>0.05) difference in weight and specific growth rate was observed among the broodfish reared under different stocking densities during the experimental period of 80 days. The broodfish stocked at a density of 357.22g/m 2 and 541.78g/m 2 spawned naturally in their respective chambers. The fish stocked at 541.78g/m 2 showed the best breeding performance. The second experiment was carried out with 4-5 days old larvae in 9 bowls of 10l capacity divided into three treatments having 20, 40 and 60 larvae each i.e. the stocking density were of 2, 4 and 6 larvae/l respectively. Larvae of treatment I which was stocked with 2 larvae/l showed significantly higher growth rate from the 7 th day of the experiment and maintained the same trend up to the end of the experiment (i.e. 21 st day) compared to other treatments. Larvae of treatment I also showed significantly higher health condition (13.31±0.69mg/mm) and survival rate (80.00±3.00) compared to those of the other two.

The present study was conducted over 4 months during 1st September to 30th December 2005 to observe the effects of stocking density on growth and survival of Thai Sharpunti, Barbodes gonionotus in 3 earthen ponds of size of 2.8    decimal each. The stocking densities of 80, 100 and 120 fish/decimal were treated as T1, T2 and T3, respectively. All    the treatments were subjected to the same feeding regime and fertilization. The range of water quality parameters    such as temperature were 30.31, 30.16 and 29.65 0C, transparency were 29.94, 37.63, and 40.02 cm, water depth    were 143.91, 148.67 and 151.54 cm, dissolved oxygen were 4.72, 4.35 and 4.24 mg/l, pH were 7.71, 7.49 and 7.31,    plankton biomass were 43.05 x 105 /l, 37.97 x 105 /l and 36.05 x 105 /l in T1, T2 and T3, respectively. Among the    growth parameters, mean weight gain were 48.87 g, 41.43 g and 34.09 g, percent weight gain were 698.21%,    591.93% and 487%, the average daily gains were 1.65, 1.54 and 1.20 g, the specific growth rate were 1.73, 1.61 and    1.47%, in T1, T2 and T3 respectively. The gross total productions of Barbonymus gonionotus were 1041.96, 1085.71    and 1019.64 kg/ha/120 days while the net productions were 911.60, 929.46 and 846.43 kg/ha/120 days in T1, T2 and    T3, respectively. The gross and net total productions in T2 were highest among the treatments. The highest growth    and survival rate were obtained in T1.   DOI: http://dx.doi.org/10.3329/jbau.v9i2.11048   J. Bangladesh Agril. Univ. 9(2): 327–338, 2011

Abstract:The study was conducted to determine a suitable feed for the desirable growth of riverine catfish Rita rita (Hamilton) from January 2006 to December 2006. The experiment had three treatments with three replicates. Nine chambers of the raceway each of size 1.83 × 1.12 sq meter were used. Local prawn, chicken viscera and commercially available formulated feed (CP) were supplied in treatment T 1 , T 2 and T 3 , respectively at the rate of 7% body weight. Feed was supplied twice in a day in the early morning and in the evening as the fish is nocturnal. The initial average weight of fish was 24.93±0.05g, 24.99±0.04g and 24.95±0.04g in T 1 , T 2 and T 3 , respectively. The final weight of the fish under three treatments was 425.05±1.04g, 425.68±1.05g and 177.61±1.45g respectively. The initial length was 8.48±0.02, 8.49±0.02 and 8.50±0.01 in T 1 , T 2 and T 3 , respectively. The final length was 25.22±0.06 cm, 25.21±0.14 cm and 14.87±0.13 cm in T 1 , T 2 and T 3 , respectively. The mean final weight and length was significantly (p<0.05) higher in T 1 and T 2 compared with T 3 . However, there was no significant difference (p>0.05) between T 1 and T 2 in terms of final weight and length was concerned. Better growth performances, however, were observed in T 2 and T 1 , where prawn and chicken viscera were supplied as feed respectively. Lowest growth performance was observed in T 3 where formulated feed (CP feed) was supplied.

To observe the effects of vitamin E on the ovarian development and breeding performances of Clarias batrachus an experiment was conducted in two phases. The first phase concentrated on studying the effects of vitamin E on ovarian development and the second phase on breeding performances. Eighty female C. batrachus broodfish were stocked in 8 cisterns (2.38 × 1.45m 2 each) divided into 4 treatments each having two replicates. Each of the cistern was stocked with 10 females. The fish were fed with feed having different levels of vitamin E viz. 0 mg (served as control), 50 mg, 100 mg and 200 mg vitamin E/kg feed for 3 months to study the effects of vitamin E on the growth and ovarian development of C. batrachus broodfish. It was found that growth in terms of body weight of fish fed with 200 mg vitamin E/kg feed (under T 4 ) was higher, while 50 mg vitamin E/kg feed (under T 2 ) gave the poorest result. There was no significant difference among different treatments. Gonadosomatic index and fecundity were highest in fish treated with 100 mg vitamin E/kg feed (under T 3 ), but there was no significant difference among the treatments. After rearing for 3 months fish were used for induction of breeding to study breeding performance. A pituitary gland (PG) dose of 100 mg/kg body weight was used in all treatments. Ovulation rate was 100% in females of all treatments. In case of fertilization and hatching rate the highest result (88.33±2.51 and 82.33±3.05 respectively) was obtained in T 2 (50 mg vitamin E / kg feed), but there was no significant difference between T 2 and T 3 . The overall result of this experiment indicates that 50 mg vitamin E/kg feed is the best dose for the breeding performance of female C. batrachus broods.

Sumithion, an organophosphate pesticide, has been used extensively in agriculture as well as in broodfish and nursery ponds in Bangladesh. Although it is being applied for beneficial purposes but eventually it exhibits some short and long term toxic effects to the aquatic ecosystem. Therefore, the present study investigated the toxic effects of sumithion on the breeding performance and subsequent viability of embryos and larvae of Heteropneustes fossilis. A total of 400 adult H. fossilis were equally stocked in two ponds. Sumithion at the dose of 0.24 ppm was applied for four months every 7 days interval in one pond while the rest one was considered as control. No significant (p>0.05) difference was found in growth between the treated and control H. fossilis; however, fertilization and hatching rates of the eggs obtained from the treated group were significantly (p>0.05) lower than that of control. Subsequently, the embryos and larvae produced from the broods of the control pond were exposed to 5 different concentrations of sumithion (0.5, 1.0, 2.0, 4.0, and 8.0 ppm) against a control (0 ppm). Each concentration was assessed in five replicates having 200 eggs. Data obtained from the sumithion acute toxicity tests were evaluated using the Probit Analysis. The mortality of embryos increased with the increasing sumithion concentrations from 0 to 8.0 ppm and the significant (p>0.05) differences were found only among the treated concentrations above 2.0 ppm. The 24 h LC 50 value for embryos was estimated to be 7.803 ppm. Dose-response decreased in hatching success and recorded as 90.8, 85.0, 76.2, 73.0, 65.0, and 51.2 % for control and 5 different concentrations of sumithion, respectively (p<0.05). The numbers of dead larvae also increased significantly with the increasing sumithion concentrations exposed for 24-96 h. The 24, 48, 72, and 96 h LC 50 values were estimated to be 8. 677, 8.245, 7.664, and 6.782 ppm, respectively and these values were significantly (p<0.05) different to each other. Besides, the larvae obtained from 0.5, 2.0, and 8.0 ppm sumithion were reared against a control for 21 days to assess the residual effect. Significant negative effects on both growth and survival of the larvae were found among the sumithion concentrations used. The study therefore, suggested that sumithion has adverse and residual effects on the breeding performance along with early embryonic and larval development of H. fossilis even in lower concentration.