Euglenophytes in aquaculture ponds - their ecology and role in fish production

The ecology of euglenophytes and their role in fish production were studied in 12 small earthen ponds beside the Faculty of Fisheries, BAU from July to November 2001. Four experiments each with three replications were conducted and those were as follows: pond treated with both poultry droppings and cowdung (T1); pond treated with only poultry droppings (T2), and pond treated with only poultry droppings (T3), while the control (T4) where no organic manure was applied. Fishes comprising of rohu (Labeo rohita), catla ( Catla catla), mrigal ( Cirrhinus cirrhosus), silver carp (Hypophthalmichthys molitrix) and silver barb (Barbonymus gonionotus) were stocked at the same stocking density of (10,621 fish/ha) and species ratio (1:1:1:2:2). The stocked fishes were fed with a common supplemental diet comprising of mustard oil cake and rice polish (1:1) at the rate of 4% of body weight per day. The highest cell density of euglenophytes was found in the ponds of T2, where poultry droppings were applied and was followed by T1, where both poultry droppings and cow dung were applied. Higher temperature, nitrate-nitrogen, phosphate-phosphorous and acidic pH were found to be conducive for the bloom of noxious euglenophytes. The bloom was found to use up most of the nutrients resulting in reduction in the growth of beneficial plankters and planktivorous fishes. The SGR (%/day) of catla, rohu and mrigal was lower during heavy bloom period while that of silver carp and silver barb were comparatively higher. The mortality of fishes in a pond of T2 during the bloom period was possibly due to formation of anoxic situation (dissolved oxygen level as low as 0.34 mg/1) in the early mornings through bacterial decomposition of the settled dead individuals or due to the combined effect of anoxic situation and toxic metabolite secretion by the euglenophytes.

Effects of black Bengal goat manure on growth and production of Genetically Improved Farmed Tilapia (GIFT) starin [sic], Oreochromis niloticus

In a goat-tilapia integrated farming system, the effect of Black Bengal goat manure on the growth and production of Oreochromis niloticus was studied at the Freshwater Substation, Shantahar, Bogra for 4.5 months. The stocking density used in three treatments were, 200 goats and 15,000 GIFT strain/ha (T1); 300 goats and 15,000 GIFT strain/ha (T2); and only 15,000 GIFT strain/ha (T3). The initial individual total length and weight of stocked tilapia were 7.6 cm and 11.34 g, respectively. Twelve ponds each having an area of 40 square meters were used for this trail [sic]. On one side of each pond goat shed was constructed and the space allocated for each goat was 0.75 m x 1.5 m. Newly weaned black Bengal goats of average weight 8.45 kg was used in the trial. Every morning the goats manure was swiped out in ponds through the fixed opening of bamboo made floor of goat shed. Water depth of the ponds was maintained at 0.75 m. The highest fish production was in treatment 1 (1,750 kg/ha) followed by treatment 2 (1,455 kg/ha) and treatment 3 (621 kg/ha). The difference in individual goat weight was not significant (P>0.05) among treatments 1 and 2.