Abstract: Field experiment was conducted to evaluate the growth performance of monosex tilapia using homemade feed with Peninsula Group fish meal and commercially available feed with local fish meal in earthen mini ponds from June-September 2010. Three ponds (T1) were supplied with prepared feed and the other three ponds (T2) with commercially available fish feed. Fish were fed at the rate of 10% of their body weight for the first thirty days then gradually reduced to 6% for the next ten days, 2% for the next ten days and 3% for remaining days. The temperature were ranged from 31.5-33.0°C, DO from 5.5-15 mg L-1 in T1 and 6.5-14 mg L-1 in T2, pH from 7.1-8.0 in T1 and 7.1-7.7 in T2, alkalinity from 105-160 mg L-1 in T1 and 100-145 mg L-1 in T2, nitrate was 0.06 mg L-1 in both treatments and ammonia from 0.02 and 0.04 mg L-1 in T1 and T2, respectively. The results of the present study showed that the best weight gain was observed as 123.48 g in T1 than T2 (111.82 g). The Specific Growth Rate (SGR) was recorded 3.09 and 2.97 and the Food Conversion Ratio (FCR) was 1.51 and 1.40 in T1 and T2, respectively. There was significant (p<0.05) variation among the survival rate (%) of fishes which were 75.55 and 90.37% in T1 and T2, respectively. The fish productions were 19076 and 16312.11 kg ha-1 in T1 and T2. The highest net profit (Taka/ha/70 days) of Tk. 15, 83,213 was obtained with T1. So, the prepared feed showed better performance with monosex tilapia in compared with commercial fish feed with local fish meal.
INTRODUCTION
Monosex tilapia (Oreochromis niloticus) is a fast growing popular cultivable fish (Chowdhury et al., 1991; Shamsuddin et al., 2012). It can easily survive in derelict water bodies at minimum oxygen level and wide range of temperature and eat all types of feed (Hussain et al., 1989). They may be cultured with low inputs which are locally available. Monosex tilapia is high yielding, excellent breeder and efficient converter to organic and agricultural wastes in to high quality protein, very hardy and resistant to disease, tolerant to over crowding conditions and able to grow in either fresh or brackish water. Tilapia, an omnivore, is assumed to be reared on number of cheaply available foodstuffs containing sizeable amount of carbohydrate. Monosex tilapia growers generally use different supplemental feeds in culture. Only natural food cannot afford high production in commercial monoculture system. Traditionally, fish meal is the preferred dietary protein source for many farmed fish species and is appreciated for its amino acid balance, vitamin content, palatability and un-identified growth factors (Azim et al., 2012; Soltan et al., 2008). Fish meal is considered the most desirable animal protein ingredient in aquaculture diets (Al Mahmud et al., 2012) because of its high protein content, balanced amino acid profiles, high digestibility and palatability and as a source of essential omega-3 polyenoic fatty acids. Among the Southeast Asian countries, Bangladesh in particular abounds with hundreds and thousands of seasonal water bodies in the form of ditches, shallow ponds, road side canals and borrow pits which retain water for 4-6 months, where carp species can not be cultured. No doubt, these water bodies have tremendous potential for aquaculture of fish species with short life cycle and characteristics of faster growth rate and require low input support (Hussain et al., 2000a). Though tilapia is not yet a widely cultured species in South Asian countries, however, its culture practices is increasing rapidly in Bangladesh. There are many homestead derelict mini ponds; proper use of those ponds with any short time culture fish like tilapia can open a new avenue for the poor farmers of Bangladesh.
Thus the aim of the present investigation was to observe the growth performance of monosex tilapia in mini earthen mini ponds using homemade feed and commercial feed.
MATERIALS AND METHODS
The experiment was conducted in 6 experimental ponds each of 0.60 decimal, located in the northern side of the Faculty of Fisheries, Bangladesh Agricultural University, Mymensingh. The study was carried out for 70 days from 26 June to 03 September 2010. The water depth was maintained at a level of 1.0-1.3 m.
To eradicate all undesirable fish, insect and other aquatic organism ponds were drained out completely. Aquatic weeds were removed manually. Lime was applied at a rate of 1 kg/decimal. Lime was soaked for overnight in a metallic container and then applied by spreading homogeneously in the ponds.
Two treatments were considered having 3 replicates in each, treatment 1 conducted with prepared feed (having Peninsula Group supplied fish meal) and treatment 2 conducted with commercially available fish feed named Quality Fish Feed (nursery-2, starter). The fries of monosex tilapia were supplied by Agro-3 Fish Hatchery and Culture farm, Bailor, Mymensingh and transported to the pond site with polythene bags having oxygenation facilities. The proximate compositions of feed ingredients were determined by using standard methods. A prepared feed (55.24% protein) composed of 37.24% fish meal, 15.00% mustard oil cake, 18.38% rice bran, 18.38% maize, 10% wheat flower and 1% vitamin premix was used in T1. Fish were fed at a rate of 10% of their body weight for the first thirty days then was gradually reduced to 6% for the next ten days, 2% for the next ten days (because, during the period water temperature was suddenly increased between 35-38°C) and 3% till the termination of the experiment. The water quality parameters were recorded throughout the experimental period. Water samples were collected between 9:00-10:00 a.m. at fortnightly interval. The physico-chemical parameters like temperature (°C), dissolved oxygen (mg L-1), pH, alkalinity (mg L-1), nitrate (mg L-1) and ammonia (mg L-1) were determined at fortnightly interval.
RESULTS AND DISCUSSION
The mean initial weight of fish in both the treatments was 15.96 g. The mean weight gains of fish at the end of the experiment were 123.48 and 111.82 g in T1 and T2, respectively. In first 30 days of culture period (stage 1), tilapia grew from 15.96 g to an average weight of 103.6 and 99.69 g in T1 and T2, respectively (Table 1). Average survival rates were 75.55 and 90.37% in T1 and T2, respectively (Table 1). Average Food Conversion Ratio (FCR) for tilapia with the prepared pellet feed and commercial pellet feed in stage 1 was 2.30 and 2.33 (Table 1). The gross production was 14174 and 12726.99 kg ha-1 in T1 and T2, respectively in the stage 1 (Table 1).
After 30 days (stage 2) of feeding, tilapia grew from 103.6 and 99.69 g to an average weight of 139.44 and 127.78 g in T1 and T2, respectively (Table 2). During the period average survival rates were 75.55 and 90.37% in T1 and T2, respectively. Average Food Conversion Ratio (FCR) for tilapia with the prepared pellet feed and commercial pellet feed were 1.51 and 1.40. Gross production averaged 19076 and 16312.11 kg ha-1 in T1 and T2, respectively during total experimental period of 70 days (Table 2).
The results of the water quality parameters such as temperature (°C), dissolved oxygen (mg L-1), pH, alkalinity (mg L-1), nitrate (mg L-1) and ammonia (mg L-1) during the experimental period are presented in (Table 3).
| Table 1: | Growth parameters of monosex tilapia in different treatments during the first 30 days of culture period |
| Table 2: | Growth parameters of monosex tilapia in treatments during the study period |
| a, b: Significant variation between treatments | |
| Table 3: | Fortnightly fluctuations of water quality parameters of the ponds under different treatments during the study period |
Among all the treatments, the highest growth rate of Oreochromis niloticus was recorded in T1. This might be associated with higher percentage of protein and lipid content of feed. Cruz and Laudencia (1998) indicated that the tilapia fingerlings need 20-30% crude protein in ration to give optimum results in ponds. The feed in T1 of the present study also contained crude protein within similar range.
In the present study weight gains of tilapia in the first 30 days were 87.65 and 83.73 g and at the end of the experiment weight gains were varied between 123.48 and 111.82 g in T1 and T2, respectively. The highest weight gain of tilapia was observed in T1 which a prepared pelleted diet with Peninsula fishing group supplied Fish Meal (FM). Supplemental feeding with formulated prepared feed resulted highest growth of Oreochromis niloticus than supplemental feeding with commercial pellet feed. Cao et al. (1998) also found similar results in case of Oreochromis niloticus fed formulated diet. Hussain et al. (2000b) and Hasan et al. (1992) reported a weight gain of about 128 g for GIFT tilapia in on-farm ponds for a culture period of 6 months fed rice bran at 5-6% of their body weight. Considering the 70 days culture period in the present study, compared to 6 months period by Hussain et al. (2000b), tilapia in the present study performed better in respect of weight gain. In the present study Specific Growth Rate (SGR) of fish in the first 30 days were 6.23 and 6.10 and at the end of the experiment specific growth rates were varied from 3.09 and 2.97 in T1 and T2, respectively. According to De Silva and Davy (1992) fish feed on supplemental feeds could show SGR value between 3-4% day-1 which is similar to the result of the present study. Diana et al. (1996) obtained SGR value of 3.10 with Oreochromis niloticus in Thailand using feed and fertilizer. On the other hand, Green (1992) obtained a slightly lower SGR value of 2.03 with tilapia in Honduras using feed and fertilizer. Hossain et al. (2004) also observed SGR value of GIFT strain ranged from 2.04-2.30 fed on formulated diet which are lower than the present value. The differences of SGR values of the species O. niloticus in the present study are due to the temperature difference during the culture period of the ponds.
In the present study, FCR value varied between 1.40 and 1.51. Lower FCR value (1.40) was obtained in T2 receiving commercial tilapia diet (31.91% protein). Hossain et al. (2004) found FCR value for GIFT strain fed on formulated diet (30.09% protein) was 1.71-1.77. The FCR values in other treatments were higher than that of T2 which could be due to the fact that rice bran, wheat bran usually contain higher crude fiber are not easily digestible.
In the present study higher survival was achieved as the fish can survive under adverse conditions like low oxygen, high temperature and high pH value. The survival rate of monosex tilapia was recorded 75.55 and 90.37% in T1 and T2, respectively during the harvesting time. During the 1st week of August, temperature increased up to 35-38°C. As a result plankton bloom occurred and then most of the mortalities were recorded during this period in both the treatments. This result does not agree with Akhteruzzaman (1998) who reported that the survival rates of Oreochromis niloticus varied from 60-80%. But the results of present study was close to the research findings of Kohinoor et al. (2007) who observed that the survival rates of monosex tilapia were varied from 79-92%.
Significantly higher production was obtained from T1 than T2. Both the treatments had similar stocking density but obtained reduced production in T2 than T1 due to produced stress in fish which lead to reduced growth and production. In first 30 days, temperature was within favorable range (31.5-33.0°C), when growth of fish in both the treatments were excellent. In the next 10 days, when temperature was increased up to 35-38°C, plankton bloom occurred which continued for 10 days, feed supply was stopped for 2 days and then reduced to 1-2% body weight. As a result fish became stressed. This is the reason of growth in the last 40 days i.e., in those days production did not achieved at the expected level. Moreover, most of the mortalities were recorded during this period in both the treatments.
In the present study, the production of fishes in first 30 days were 14174 (kg ha-1) and 12726.99 (kg ha-1) and then next 40 days were 4902 and 3585.12 kg ha-1 and total fish production were 19076 and 16312.11 kg ha-1 in T1 and T2, respectively whereas i.e., in 70 days. Thakur and Das (1996) and Akhteruzzaman (1998) mentioned that the average yield was 1800 and 150-500 kg ha-1, respectively in 5-6 months. These results are much lower than the findings of the present experiment.
A simple economic analysis of the growth performance of fish showed that highest net profit (Tk/ha/70 days) of Tk. 15, 83,213 was obtained with T1. The highest profit in T1 is due to good proximate composition of feed prepared with Peninsula group supplied fish meal than commercial tilapia feed. On the other hand, fish fed prepared feed supplied by Peninsula Fishing Group also showed more profit than fish fed commercial tilapia diet (T2).
In the present study, when we consider growth, SGR, production, FCR and economic value in the treatment 1 which yield significantly better results. In the diet of prepared feed, the fish meal was specially supplied to Agro-3, Fish Hatchery, to compare growth performance with local fish meal. It was observed that feed prepared from Peninsula Group supplied fish meal yielded better performance with monosex tilapia. Thus during feed formulation quality ingredients is a must for improved fish growth and production. It can be mentioned here that the supplied fish meal from Chittagong area possesses higher protein percentages in comparison with local one and thus yielded higher production compared with local fish feed.