M. R. Islam
Department of Fisheries, Faculty of Biological Sciences, University of Dhaka, Dhaka-1000, Bangladesh
M. R. Hassan
Zoology Section, Biological Research Division, Bangladesh Council of Scienti?c and Industrial Research (BCSIR), Dhaka-1000, Bangladesh
M. Begum
Zoology Section, Biological Research Division, Bangladesh Council of Scientific and Industrial Research (BCSIR), Dhaka-1000, Bangladesh
N. J. Punom
Department of Fisheries, Faculty of Biological Sciences, University of Dhaka, Dhaka-1000, Bangladesh
M. K. Begum
Department of Fisheries, Faculty of Biological Sciences, University of Dhaka, Dhaka-1000, Bangladesh
N. Sultana
Zoology Section, Biological Research Division, Bangladesh Council of Scienti?c and Industrial Research (BCSIR), Dhaka 1000, Bangladesh
M. S. Rahman*
Department of Fisheries, Faculty of Biological Sciences, University of Dhaka, Dhaka-1000, Bangladesh
Moina macrocopa; Nile tilapia Oreochromis niloticus; Live food; Growth performance; Body composition
Department of Fisheries, Faculty of Biological Sciences, University of Dhaka, Dhaka-1000, Bangladesh
Animal Health and Management
Experimental design The whole experiment was designed for 2 types of culture; a) culture of live zooplankton M. macrocopa and b) culture of experimental fish fry of Tilapia, O. niloticus. Experiment 1: Effects of different diets on rearing M. macrocopa The experimental organism, M. macrocopa samples were collected from various places of Gulshan Lake (about 23º48' N latitude and 90º25' E longitude), the northernmost lake in a chain of water bodies located in Dhaka city and carried to the laboratory located in Zoology Section, Biological Research Division, Bangladesh council of Scientific and Industrial Research (BCSIR). Samples of M. macrocopa were easily collected in winter (November) from the water surface by sieve number 270 (mesh=0.05 mm) and kept in cool and dry place. The collected M. macrocopa was identified according to Brooks (1959). To prepare M. macrocopa stocks, collected samples were kept in aquarium at a temperature of 25 ± 2 ºC and having pH of 7.5 and aerated vigorously. After 7 days, aeration was stopped and they were removed to some new aquaria by siphoning out. Before starting the main experiment, they were fed with Spirulina flake. During stock maintenance, culture was examined daily, all exuviae and any dead individuals were removed and up to 50% of water was also changed twice a week. M. macrocopa was semi continuously cultured for 30 days. The culture was designed as four treatments and each treatment had two replications. Treatment-1 was fed with handmade feed, treatment-2 was fed with cabbage leaves, treatment-3 was fed with yeast and treatment-4 was fed with Spirulina (Spirulina platensis) flake. Mass cultivation of M. macrocopa was carried out in eight aquariums of size 0.9m× 0.46m × 0.6m with 24 hours aeration having 60 liters of tap water under natural light illumination at a temperature of 25 ± 2°C adjusted by using thermostatically controlled heaters, pH 7 ± 1 and a dissolved oxygen level of 3-6 mg/L. The tap water was left one day for seasoning. On the 2nd day feed was applied in the aquarium according to the experimental design. On the 3rd day, 200 individual of M. macrocopa was stocked to each aquarium. To count the population of zooplankton 1000 ml of culture water was sampled randomly and then in 1 ml of that water was taken by a dropper and number of zooplankton was counted. Finally total population density was determined according to the formula outlined by Ovie (1991): Pd= 100×Bx/ V ml, where Pd =population density of M. macrocopa in 1000 ml of water, V= Average volume of water sample, Bx = Average number of M. macrocopa counted in various random sampling. Experiment 2: Effects of M. macrocopa on culture of Tilapia fry The culture of O. niloticus was conducted for 56 days. The experiment was designed as three treatments where treatment-1 was fed with handmade feed (control), treatment-2 was fed with commercial feed & treatment-3 was fed with live food M. macrocopa (fed Spirulina). The proximate composition of the experimental diets are shown in Table I. The experimental homemade feed was combined with fish grain 13.7%, shrimp grain 13.7%, soybean 13.7%, Wheat 14.5%, vitamin and minerals 0.85%, corn grain 14.5%, rice bran 14.5%, oil cake 13.7% and fat 0.85%. Six culture aquariums of 1.1m × 0.46m × 0.3m were washed, drained and left to dry for a couple of day prior to the beginning of the experiment. The experimental aquariums were disinfected by 70% alcohol prior to the experiment started. Fry of Tilapia (O. niloticus) (2.87 ± 0.04 cm and 0.424 ± 0.03 g) were collected from Mymensingh and carried in oxygenated bags with water in the laboratory located in Zoology Section, BCSIR Lab, Dhaka. Before stocking, Tilapia fry were acclimated in laboratory conditions at a temperature of 25 ± 2°C adjusted by using thermostatically controlled heaters, pH 7 ± 1, 24 h continuous aeration and a dissolved oxygen level of 3-6 mg/L for 24 h without supplying any food. The fry were randomly distributed at a rate of 30 fry per aquarium. The three diets were fed to the experimental fish in six replicate aquariums per dietary treatment. Feeding was done twice daily at 90-400 Moina/individual fish for first 20 days, then 500-850 Moina/individual fish for 15 days and 900-1250 Moina/individual fish for remaining days. Each ration was divided into two equal parts, one portion was offered at 10.00 am while the other at 5.00 pm. Partial exchange of water from each aquarium was done daily during the removal of uneaten feed and faeces. Physico-chemical parameters of water such as temperature, dissolve oxygen, pH, conductivity, total dissolve substance and light intensity were recorded twice in a week. Sampling was performed in the 14th, 28th, 42th and 56th day of the experimental period and, length and weight of individual fish were recorded for further analyses. Growth indices Fish growth performance was calculated using the following formulae: a) Condition factor, K= W/ L 3× 100 Where, K= Condition factor, W= Body weight in grams and L= Body length in centimeters b) Average Daily Gain (ADG, g/day) = (Mean final weight - mean initial weight) /time interval (days) c) Specific Growth Rate (% day) = (Loge final weight - Loge initial weight) /time interval (days) ×100 d) Feed Conversion Ratio (FCR) = Feed consumed by the fish / weight gain by the fish e) Survival Rate (%) = Number of fry that survived / Total no. of fry stocked ×100 Body composition analysis At the end of the 56-day rearing period of Tilapia fry total protein (micro-Kjeldahl method), total lipid, ash and moisture content were determined (AOAC, 1995). Moisture content was estimated by drying the samples to constant weight at 105°C in a drying oven and nitrogen content using a micro-Kjeldahl apparatus (Automatic Kjeldahl Digester, DKL 8 Series, VELP Scientifica, Italy and Kjeltec 2100, Distillation Unit, FOSS Analytical, Denmark). Crude protein was estimated by multiplying nitrogen content by 6.25. Lipid content was determined by ether extraction in a multi-unit Soxhlet extraction apparatus for 16 h. Ash was determined by combusting dry samples in a Muffe Furnace at 550°C for 6h. Statistical analysis Data were analyzed by using one-way ANOVA followed by Tukey’s HSD post hoc for multiple comparisons. The data were presented as mean ± SEM and evaluated by using the statistical package of SPSS (version 20.0) with the level of significance at p<0.05.
Bangladesh J. Sci. Ind. Res. 52(2), 81-88, 2017
Journal