Pinky Debnath
Department of Fish Biology & Genetics, Sylhet Agricultural University, Sylhet-3100, Bangladesh
Sajib Kumar Chowdhury
Department of Fish Biology & Genetics, Sylhet Agricultural University, Sylhet-3100, Bangladesh
Nirmal Chandra Roy
Department of Fish Biology & Genetics, Sylhet Agricultural University, Sylhet-3100, Bangladesh
Oreochromis niloticus, Dietary salt, Supplementation, Growth, Feed utilization
Post-graduate laboratory of the Department of Fish Biology and Genetics, Faculty of Fisheries, Sylhet Agricultural University, Sylhet
Animal Health and Management
Tilapia, Feed, Salt
2.1 Study Area: The experiment was conducted inside the Post-graduate laboratory of the Department of Fish Biology and Genetics, Faculty of Fisheries, Sylhet Agricultural University, Sylhet. The experiment was carried out for a period of 21 days from 18 May to 7 June 2016 in 12 aquariums.
2.2 Collection and acclimatization of tilapia fry Healthy and uniformed sized Tilapia (Oreochromis niloticus) fry were collected from a private hatchery (Pirojpur Fishery Khamar, Dakhsin Surma, Sylhet) and kept into an oxygenated polybag. Before stocking fry were acclimatized to the aquarium water gradually for one hour.
2.3 Experimental design The experiment was laid out in a Completely Randomized Design (CRD) using 100 liters aquarium each stocked with 30 fry. Four treatments with three replicates for each were used for the experiment. The treatments were designated as T1 (control), T2, T3 and T4. T1 contains 0%, T2 contains 1.0%, T3 contains 1.5% and T4 contains 2.0% dietary salt in diet, respectively.
2.4 Supplemented diet The stocked fry of tilapia were fed with commercial starter feed (containing 32% protein) at the rate of 20-10% of body weight twice daily.
2.5 Experimental Procedure Tilapia fries were collected from a commercial hatchery with initial mean weight of 2.2±0.01 g and initial mean length of 5.0±0.01 cm and kept in 100 liter rectangular aquarium for 2 hours acclimatization. After acclimatization weight and length were recorded and fries were stocked in aquarium according to the design of the experiment. The aquarium was provided with sand and iron filtered freshwater (2 lmin-1) and with continuous aeration to maintain the dissolved oxygen level near saturation. Tilapia were fed twice daily at 09.00 am and 4.00 pm. Fish were weighed in bulk every week and measured the length until the ending of the experiment (3 weeks). Fecal matters were removed by siphoning each morning before morning feeding and at each afternoon before afternoon feeding and half of the water replaced with the filtered water twice daily after the removal of the fecal matters and before the feeding. Mortality was cheeked daily. The experiment was conducted at ambient temperature with a natural photoperiod (approximately 12 h light and 12 h dark). Water temperature and salinity were monitored daily between 08.00 to 09.00 am, while pH and dissolved oxygen were monitored twice weekly. Every 7 days intervals in the morning (9.00 to 10.00 am), approximately 15 h after the last feeding all fish were counted and randomly selected 6 fishes were weighted from each replication to determine weight gain, specific growth rate and length increment. Weight was taken with a spring balance (DONGIL-15 kg x 50 g) and length was measured with a measuring scale. All the data were recorded in a note book and finally calculated the average length and weight of fishes according to treatment on each sampling day. After taking the data, all the fishes were kept to their own aquarium carefully. At the ending of the 3 weeks experiment, all fishes were counted and individually weighted to determine the survival, weight and length.
The following formulae were used to evaluate the growth: a) Length gained = Mean final length – Mean initial length b) Weight gained = Mean final weight – Mean initial weight.
2.6 Statistical analyses Growth, survival and production parameters were analyzed using one way analysis of variance (ANOVA) to compare the treatment means. If the main effect was found significant, the ANOVA was followed by Duncan’s Multiple Range Test (DMRT) at 5% level of significance using SPSS version 22.
International Journal of Fisheries and Aquatic Studies 2017; 5(6): 275-280
Journal