Abstract: Background and Objective: To maintain the current production rate with a consistent acceleration, more research on farming procedures, survival rate, feed conversion capability and growth performance of Cirrhinus mrigala in a confined cultural environment is needed. Therefore, this research aimed to determine the optimal feeding rate at which Cirrhinus mrigala, can develop at its best, with the highest survivability and feeding conversion capability in cages. Materials and Methods: A nine-week research was carried out to assess the growth and survivability of Cirrhinus mrigala in two separate cage treatments. The cages were all the same size and shape and the stocking density in each treatment was 280 per decimal. T1 and T2 received formulated feed and were fed 10 and 7% of their body weight, respectively. Results: The initial mean weight of fish was 25.4±1.63 g in each treatment. Net weight gain in T1 and T2 were found 44.4 and 35.4 g while mean weight gain in percentage was found 74.80 and 39.37% in T1 and T2 , respectively. The mean final length attained at the time of harvesting in T1 and T2 were 17.9±0.26 and 17.5±0.44 cm where the initial length was 9.6±0.83 cm for both treatments. The FCR was found to be lower in T2 than in T1, with values of 5.78 and 4.62 in T1 and T2, respectively, in this study. Temperature, pH and DO were all between 30-32.5°C, 7.3-7.85 and 4.7-6.6 mg L–1, respectively. In T1 and T2, survival rates were found to be 90 and 85%, respectively. Conclusion: Cirrhinus mrigala showed better growth and survival rates when fed 10% of their body weight (T1) compared to 7% (T2) in this experiment, indicating that a 10% feeding rate can be beneficial for cage culture.
INTRODUCTION
Mrigal (Cirrhinus mrigala, Hamilton)1, an Indo-Gangetic riverine carp, is one of three Indian large carp species commonly cultivated in Southeast Asian countries. This species has a long history of being used in polyculture with other native species, especially in India. However, records of its culture date from the early twentieth century. In the early 1940s, it was introduced for aquaculture to other areas of India outside its natural range, along with Catla (Gibelion catla) and Rohu (Labeo rohita) and in the 1950s and 1960s to Bangladesh, Pakistan, Myanmar, the Lao People's Democratic Republic, Thailand and Nepal2 and has also been introduced into Sri Lanka, Vietnam, China, Mauritius, Japan, Malaysia, Philippines and the former USSR3.
Cirrhinus mrigala (Mrigal) has established itself as one of the most important component species in pond culture due to its initially faster growth rate and compatibility with other carps. Mrigal is eurythermal, meaning this species can withstand temperatures as low as 14°C. Mrigal can grow up to 1 m in length4. The species usually reaches 600-700 g in the first year of cultivation, depending on stocking density and management practices. Mrigal grows more slowly than catla and rohu among the three big Indian carps2.
Successful aquaculture depends exclusively on water quality, primary productivity, stocking density, culture system, fish species and quality of artificial feed and genetic variance of species. The primary productivity of a water body depends on some common physical factors such as temperature and transparency as well as chemical factors such as Dissolved Oxygen (DO), pH etc and without primary productivity aquatic production is not possible. Some researcher5-10 explained the necessity of water quality for fish culture and mentioned the level of some physicochemical parameters like as temperature range is 25-32°C, transparency from 25-45 cm, DO from 5.0- 8.0 mg L–1 and pH from 6.5-8.5.
The right amount of feed must be given each time to prevent overfeeding or underfeeding the fish. The amount of feed to be given to the fish per day, known as the feeding rate (ration), is determined by the fish's weight. To meet their metabolic energy needs, fish change their food intake rates.
The amount and quality of feed consumed has a significant impact on the growth rate, feed conversion efficiency and chemical composition. Shivagami et al.11 recorded higher feed consumption at an 8% feeding regime and lower feed consumption at a 4% feeding regime in their experiment. Desai et al.12, on the other hand, found that a 6% body weight/day ratio is ideal for common carp development at temperatures between 28 and 32 °C. The best growth output of Cirrhinus mrigala was recorded by Khan et al.13, with the feed at 4-6% body weight of total biomass. Farming procedures, feed conversion ability, growth efficiency and survival rate among other things are important determinants of aquaculture success. That is why, while cultivating Mrigal in a restricted cultural context, it is critical to research these factors to maintain the current production rate at a consistent rate of acceleration. As a result, this study was carried out to learn about Mrigal's growth in response to commercial feed in various rations as well as to save money on feeding by observing the FCR value.
MATERIALS AND METHODS
Study area: For this experiment, an adjacent pond was used which located at Noakhali Science and Technology University (22°47 31 N 91°06 07 E) in Bangladesh and conducted during the period from 07 August to 13 October, 2017 for 9 weeks.
Experimental design: For nine weeks, the experiment was performed in an enclosure. Treatments 1 (T1) and 2 (T2) were used in the experiment, with feed rates of 10 and 7% of the fish's body weight, , respectively. Those two procedures were carried out in two separate cages with a 0.0723 decimal area and dimensions of 8×4×4 feet each. Between the cage and the embankment, there was a gap of 100 cm.
Preparing the water body before setting the cage: Manual uprooting of rooted weeds in the pond embankment. The hand net was used to keep track of floating weeds. For weed control, no chemicals were used. During the entire experiment, aquatic insects and other potentially harmful species like crabs were manually monitored. The installation of a bamboo pile in the dike helped to prevent soil erosion. The bottom was cleaned of excessive sedimentation.
Installed the cage: Bamboo, nylon net and jute fibre were used to make the cages which were all readily available in the region. The cage was designed to hold a one-meter distance between it and the dike. The pond bottom and the net bottom are separated by one foot.
Stocking of fry: The average length and weight of 40 days old fry were 9.60±.83 cm and 25.4±1.63 m, respectively, which are collected from a nearby fish hatchery. During the morning, fry were transported in an oxygenated polybag. Three days after setting up the experimental enclosure, the fry was acclimatized using the same pond water as the experiment. For both procedures, fish fry was stocked at a density of 20 per cage in Table 1.
| Table 1: Stocking density in treatments (T1 and T2) | |||
Area of the |
No. of fish/ |
No. of fish/ |
|
| Treatment | cage (decimal) |
decimal |
cage |
| T1 | 0.0723 |
280 |
20 |
| T2 | 0.0723 |
280 |
20 |
| Table 2: Proximate Composition of supplemental feed fed to Mrigal | |
| Feed ingredients | Amount of feed (%) |
| Fish meal | 34.1 |
| Mustard oil cake | 16.2 |
| Wheat flour | 10.6 |
| Bone meal | 9.3 |
| Cornflower | 11.3 |
| Rice bran | 16.5 |
| Starch | 2 |
| Total | 100 |
| Proximate analysis | |
| Crude protein | 31.6 |
| Crude fiber | 37.8 |
| Moisture | 9.6 |
| Fat | 7.1 |
| Ash | 13.9 |
Management of feeding: Fish meal, mustard oil cake, wheat flour, cornflower, rice bran, bone meal and starch were used in this experiment to create a sinking diet. During the formulation of the feed, the diameter size was kept constant at 2.00.3 mm. The diet used in the experiment had a nutritional composition of 94% Dry Matter (DM), with 31.6% Crude Protein (CP), 37.8% Crude Fiber (CF), 7.1% fat and 13.9% ash in Table 2. In this experiment, the protein was determined using the Kjeldahl method, fat was determined using the Soxhlet method, moisture was determined using the oven drying method, fibre was determined using the acid detergent method and ash was determined using the muffle furnace method. Directly thronging from hand, the feed was spread uniformly over the surface of the water inside the cage. The first half of the ration was provided at 8 am and the second half was provided at 4 pm. The amount of feed to be given adjusted after calculating the biomass of the cage every week.
Sampling and measurement: A scope net was used to capture the fish and a scale and a digital balance (Lutron GM-600.0 g×0.1 g) were used to measure the length and weight of each fish. To reduce sampling error, 30% of the total fish were sampled at each period. A pH meter (model: HANNA-HI96107) was used to calculate the pH of the water. A portable DO meter (Lutron-DO-5509) was used to measure dissolved oxygen twice a week The following formula was used to measure growth efficiency (weight and length), survival rate, Specific Growth Rate (SGR) and Feed Conversion Ratio (FCR) in this experiment14:
Statistical analysis: All data were subjected to make graph and table using MS Excel.
RESULTS AND DISCUSSION
Water quality parameters: Physical, chemical and biological environmental parameters were interrelated in a complicated sequence of physiochemical reactions15 and each aspect of fish culture was affected (survival, growth and reproduction). Temperature, pH and dissolved oxygen changed over time in this experiment but clarity remained nearly constant. T1 and T2 had weekly average temperatures of 31.3±1.001 and 31.1±0.661°C, respectively in Fig. 1. The experimental cage temperature was within the appropriate range for culture ponds, which is consistent with the other findings16-18 but the temperatures of both cages were slightly higher for mrigal culture4,19.
In T1 and T2, the weekly average pH ranged from 7.22-7.85 and 7.27-7.74, respectively, with mean (SD) values of 7.52±0.186 and 7.483±0.149 Fig. 2. The pH values of both T1 and T2 agree well with the findings4-6,9.
The weekly average DO (mg L–1) was ranged from 5.0-6.6 and 4.7-7.2 mg L–1 with a mean SD value of 5.71±0.592 and 5.667±0.795 mg L–1 in T1 and T2, respectively in Fig. 3. The level of Dissolved Oxygen (DO) was within the acceptable range in this study in accordance with the other studies4,7,10.
Growth performance: The growth curve was upper in T1 compare to T2 in Fig. 4. T1 and T2 achieved average final weights of 69.8±7.3 and 60.8±9.09 g, respectively, at harvest, where the initial weight was 25.4±1.63 g for both treatments (Fig. 5). Shivagami et al.11, who discovered that Mrigal showed developed better in higher feeding rations than lower feeding rations, agreed with this study.
| Fig. 1: | Weekly average temperature in both treatments |
| Fig. 2: | Weekly average pH in both treatments |
During the study period, T1 and T2 had net weight gains of 44.4 and 35.4 g, respectively in Fig. 5. In T1 and T2, weekly weight gain ranged from 3.6-6.4 and 2.8-4.8 g, respectively, with mean SD values of 4.93±0.75 and 3.93±0.72 g in Table 3. In other studies, the weight gain of Mrigal was 62-8120 and 57.06 g21 which was close to the present treatment of T1. Observed in the present study, mean weight gain in percentage was 74.80 and 39.37% in T1 and T2 respectively and another finding was 13.64-85.71% in case Indian major carps11. Mean final weight and net weight gain of both T1 and T2 based on mean initial weight are given in Fig. 5 which showed the comparison between the growth performance of Mrigal.
The Specific Growth Rate (SGR) of mrigal in T1 and T2 were found 1.6±0.71 and 1.38±0.50% respectively in Table 4. The SGR value in both treatments was lower compare to the findings of Biswas et al.20, Zhen-Yu et al.21, Desai et al.12, Abdelghany et al.22, Jena et al.23, Hossain et al.17 and Sahu et al.4 where they found the SGR of Indian major carps (rohu, catla, mrigal) and common carps usually ranged between 2.0-4.0%.
| Table 3: Weekly weight gain of mrigal, (Cirrhinus mrigala) | |||||||||
| Weight gain (g)/weeks | |||||||||
| Treatment | 1st |
2nd |
3rd |
4th |
5th |
6th |
7th |
8th |
9th |
| T1 | 6.4 |
5.4 |
4.4 |
3.6 |
5.2 |
4.8 |
5.0 |
4.8 |
4.8 |
| T2 | 4.8 |
4.0 |
3.2 |
3.2 |
4.8 |
2.8 |
4.4 |
4.2 |
4.0 |
| Table 4: Specific growth rate of both T1 and T2 treatments | ||||||||||
| SGR (%) (weeks) | ||||||||||
| Treatment | 1st |
2nd |
3rd |
4th |
5th |
6th |
7th |
8th |
9th |
Avg. |
| T1 | 3.21 |
2.24 |
1.6 |
1.19 |
1.55 |
1.3 |
1.24 |
1.1 |
1.02 |
1.6±0.71 |
| T2 | 2.47 |
1.77 |
1.27 |
1.17 |
1.6 |
0.85 |
1.24 |
1.1 |
0.97 |
1.38±0.5 |
| Fig. 3: | Weekly average dissolved oxygen in both treatments |
| Fig. 4: | Mean body weight in gram changes of different treatments at a week interval |
| Fig. 5: | Comparison among mean initial body weight, final body weight and net weight gain between the treatments (T1 and T2) |
| Fig. 6: | Mean body length changes of different treatments (T1 and T2) at a week interval |
| Fig. 7: | Weekly length gain comparison between T1 and T2 |
| Fig. 8: | Mean initial body length, final body length and net length gain between the treatments |
| Fig. 9: | Comparison between FCR values of T1 and T2 |
| Fig. 10: | Comparison between survivability of T1 and T2 |
T1 had the highest length (18.2 cm) compare to and T2 (17 cm) at the harvesting period in Fig. 6. This study showed similarities with the findings of Ayyappan and Jena2 and Hossain et al.17, they showed the length of mrigal had a tendency to increase in higher feeding ratio. Weekly average length gain ranged from 0.2-2.3 and 0.2-2.6 cm with mean SD value of 0.92±0.62 and 0.87±0.75 cm in T1 and T2 respectively in Fig. 7. Net length gain for both T1 and T2 were found 8.3 and 7.9 cm respectively in Fig. 8. The range of final length was found to vary from 17.5-18.2 cm and 17-18.1 cm respectively in T1 and T2 where the average length was 17.9±0.26 and 17.5±0.44 cm at harvest, respectively but the initial length was 9.6±0.83 cm for both treatments (Fig. 8). In the first four weeks, both T1 and T2 treatments displayed a greater average weekly weight gain.T1showed a higher average weekly gain than T2 similar to the findings with Shivagami et al.11.
Feed conversion ratio: The FCR was lower in T2 than in T1, FCR was found 5.78 and 4.62 in T1 and T2 respectively in Fig. 9. The FCR of both treatments were higher in comparison with the study of Khan et al.13 in which he found that Mrigal showed higher FCR with the use of 4-6% body weight feed. The present study showed dissimilarities with the result of Shivagami et al.11 and Biswas et al.20, where they found FCR value 3.02 and 0.65-0.91 at the different feeding ration of total body weight. FCR values of T2 treatments showed close to the other studies24-26 where they found that FCR values of Indian major carps ranged from 1.97-4.91.
Survival rate of C. mrigala: T1 also had the highest survival rate, while T2 had the lowest. In T1 and T2, survival was found to be 90 and 85%, respectively, while the initial stocking number of fish was 20 in both treatments in Fig. 10. Similar finding (83.9-91.7%) were reported by Sahu et al.4 and was dissimilar studies (27.12-48.02)20.
CONCLUSION
In this experiment, fish in treatment 1 (T1) grew faster than other treatment 2 (T2), where feed was given at a rate of 10% of the fish's body weight. So, based on the current experimental situation, Mrigal growth is higher in high feeding percentages.
SIGNIFICANCE STATEMENT
This study discovered the growth performance of C. mrigala in cages that can be beneficial for fish culturists. Feed ratio has been improved in the present study which ultimately leads to higher production of this species. This study will help the researchers to uncover the critical areas of the feasibility of mrigal culture in the cage with different feeding rate that many researchers were not able to explore in the past. Thus a new theory on the growth improvement of C. mrigala may be arrived at by the present research.