IMPACT OF STOCKING DENSITY ON GROWTH AND PRODUCTION PERFORMANCE OF VIETNAMESE KOI ( Anabas testudineus ) IN SEMI-INTENSIVE CULTURE SYSTEM AT MUKTAGHASA REGION OF MYMENSINGH DISTRICT Gias

Stocking density is considered one of the important factors affecting fish growth. The study was aimed to compare the growth parameters of Vietnamese Koi (Anabas testudineus ) at various stocking densities. The experiment was carried out during the period from 01 September to 30 November 2014. Three stocking densities were used as 150, 250 and 350 fries/dec and designated as treatment T 1 , T 2 and T 3 respectively each having two replicates. The average size of each pond was 33 decimal with an average depth of 5 feet. Quality fish feed was used three times daily throughout the culture period. From this experiment, it was found that the highest net profit was BDT 32,690 in T 1 followed by BDT 36,104 in T 2 and BDT 38,450 in T 3 . That time the market price was BDT 130/kg fish. Culture of Vietnamese koi at stocking density (150 fish/dec) showed higher benefit in short period of time. The benefit cost ratio was 1.7, 1.63 and 1.56 in T 1 , T 2 and T 3 , respectively. From the present experiment, it was found that the total production was increased with the increase of stocking density. But the individual fish growth rate was decreased with the increase of stocking density. Res. Agric., Livest. Fish.2(2): 335-341, August 2015


Vietnamese Koi Production Performance Semi-intensive Culture System
Stocking density is considered one of the important factors affecting fish growth.The study was aimed to compare the growth parameters of Vietnamese Koi (Anabas testudineus) at various stocking densities.The experiment was carried out during the period from 01 September to 30 November 2014.Three stocking densities were used as 150, 250 and 350 fries/dec and designated as treatment T1, T2 and T3 respectively each having two replicates.The average size of each pond was 33 decimal with an average depth of 5 feet.Quality fish feed was used three times daily throughout the culture period.From this experiment, it was found that the highest net profit was BDT 32,690 in T1 followed by BDT 36,104 in T2 and BDT 38,450 in T3.That time the market price was BDT 130/kg fish.Culture of Vietnamese koi at stocking density (150 fish/dec) showed higher benefit in short period of time.The benefit cost ratio was 1.7, 1.63 and 1.56 in T1, T2 and T3, respectively.From the present experiment, it was found that the total production was increased with the increase of stocking density.But the individual fish growth rate was decreased with the increase of stocking density.

INTRODUCTION
Climbing perch Koi (Anabas testudineus) is an important indigenous fish species of Bangladesh which is very popular for its delicious taste and flavor.According to Saha (1971), the fish contain high values of physiologically available iron and copper essentially needed for hemoglobin synthesis.Once climbing perch was abundantly available in almost all freshwater systems of Bangladesh, however, recently population of this fish has been declining very rapidly.The reasons for such decline are many, such as ecological degradation, indiscriminate fishing, use of pesticides and fertilizers, destruction of habitats, obstruction to breeding migration, management failure, etc.In the face of diminishing natural population of climbing perch-planners, policy makers, aqua culturists, and fisheries biologists are thinking of its cultivation through intensive farming (DOF, 2002).For efficient culture and management of fisheries resources, an understanding of the various factors which have profound influence on the productivity of the water bodies is necessary.
Monoculture and polyculture are practicing culture technique in Bangladesh.The climbing perch fish Anabas testudineus (Bloch) is one of the important freshwater fish of Bangladesh which is locally known as koi in different places of Bangladesh.It contributes 1.4% in the total inland water fish production (DoF, 2011(DoF, -2012)).This species considered as a valuable item of diet for sick and convalescent.The breeding technology of native koi (A.testudineus) had successfully been developed in BFRI (Kohinoor, 1991).But the growth rate is very slow in comparison to Thai koi A. testudineus.Its slow growth and small size does not favour sustainable production per unit area in aquaculture system (Kohinoor et al., 2009).To overcome this situation, another fast growing climbing perch known as Thai koi (A.testudineus) has been introduced from Thailand in 2002.Although the Thai koi ( A. testudineus) is presently used for production purposes by large number of farmers but it is not widely accepted by consumers owing to its body covers with gray colour; small black spots and lack of taste in comparison to native koi ( A. testudineus).To improve this situation, another variety of koi known as Vietnamese koi (A.testudineus) have been imported from Vietnam in 2013 by Sarnolata Agro Fisheries Ltd; which is believed to give higher production and faster growth than other variety of koi.A recent report made known that Vietnamese koi grows as big as 250-300g within 4 months culture period with a good FCR and similar body color as native koi.(Sarnolata Agro Fisheries Ltd; 2013).Present study was undertaken to observe the growth performance of Vietnamese koi (A.testudineus) in semi-intensive culture system.

MATERIALS AND METHODS
This experiment was conducted in "Noha Aqua Farm" at Muktagasha region of Mymensingh for a period of three months from 1 th September 2014 to 30 th November 2014.

Collection of fry
The fry of Vietnamese koi were collected from "Desh Bondhu Matshaya Hatchery", Mymensingh.

Selection of feed
Commercial pellet feed named "Quality Fish Feed" was selected for the present experiment.The Proximate composition of Quality fish feed were Moisture (Max) 12%, Protein (Min) 35%, Lipid (Min) 3% and Fiber (Max) 10%.

Stocking of fry
Vietnamese koi fry were 1.0g each at the time of directly stocking to the pond.

Feeding Strategy
At the beginning of the experiment feed was supplied at the rate of 100% of the body weight of reared Vietnamese koi (1-8 days) and gradually it was readjusted to 40% (9-20 days), 20% (21-30 days), 10% (31-40 days), 5% (41-60 days) and finally up to harvest at 3% body weight (61-90 days).No additional feed was supplied.Fish were feed three times daily.

Monitoring and data collection
Growth monitoring was done at 10 days interval.Fish were caught with the help of cast net.The weight recorded by random sampling of Vietnamese koi with the help of electrical balance.

Data analysis
Data obtained from the present study were analyzed statistically to observe growth performance of different fish species.

RESULTS AND DISCUSSION
The results of the present experiment regarding compositions of water quality Parameters and growth performance of Vietnamese koi are presented below:

Water quality parameters Physical and chemical parameters
The results of the physical and chemical parameters recorded during the experimental period presented in the Table 2 and Table 3.

Table 2.
Fluctuations of physical parameters in culture pond during the experimental period Wahab et al. (1994) found transparency ranging from 15-55 cm in polyculture pond.Kohinoor (2000) recorded transparency ranging from 15 to 58 cm.In the present experiment, the transparency values in treatment-1, 2 and 3 were closely near to productive range (28 to 32 cm).Aminul (1996) stated that the water temperature ranged from 22 to 34 °C was suitable for culture of fish.In the present study, range of water temperature was more or less near suitable range for fish culture (19.55 to 29.50 °C).
Table 3. Fluctuations of chemical parameters during the experimental period Kohinoor (2000) measured dissolved oxygen 2 to 7.4 mg/l in the research ponds of Bangladesh Agricultural University campus, Mymensingh.From the above findings, it was concluded that the oxygen content of the present experimental ponds were within the good productive range.During the study period the average fluctuations of free carbondioxide in replication-1, 2 and 3 were range from 2.30 to 3.23 mg/l.The mean values of free carbondioxide were 2.810.35mg/l in three replication.Israfil (2000) and Kabir (2003) observed more or less similar results.Fluctuations of the pH values of the experimental treatments ranged from 6.90 to 7.43.The mean values of pH were 7.12 ± 0.23 in three replication.Dewan et al. (1991) stated that the optimum pH range for carp polyculture in pond is 6.5 to 9.0.Israfil (2000) and Kabir (2003) found almost similar results.According to Rahman (1992) total alkalinity of productive ponds should be 20 ppm or more.Total alkalinity in the experimental treatments ranged from 48.00 to 53.00 mg/l.The mean values of total alkalinity were 50.58 ± 1.98 mg/l inthree replication.From the above discussion, it may be concluded that all the parameters of experimental ponds were suitable for fish culture.Cost-benefit analysis From the experiment it was found that the cost of three treatments were BDT 47000, 57236 and 67500 in T1, T2 and T3 respectively.Production (kg/Treatment) was 613 kg in T1, 718 kg in T2 and 815 kg in T3 and price of fish per kg was BDT 130 for each treatment.

Net profit
The net profit in three treatments was BDT 32,690 in T1, BDT 36,104 in T2 and BDT 38,450 in T3.

Cost-benefit Ratio
The Cost-benefit Ratio in three treatments was 1.70 in T1, 1.63 in T2 and 1.56 in T3.

Mean weight gain (g)
There was significant difference (p≤ .01)among the different treatments.The highest mean weight gain (121.92 ± 1.32g) was found in treatment T1, whereas the lowest mean weight gain (75.92 ± 2.65g) was found in treatment T3.The present experiment showed the highest mean weight gain of fish in treatment T1 which was stocked at lower densities although same feed and feeding rate were applied in all the treatments.These phenomenon indicated that lower stocking density reduces competition among the fishes which influenced them to take feed properly and it might be absent in the treatments with higher stocking densities.Ahmed et al. (2013) obtained a weight gain of 123.48 g and 111.82 g from two different treatments of monosex tilapia for a period of 70 days which were more or less similar to the present study.Ahmed et al. (2015) found the mean lowest weight gain (94.45g) which is higher to our present findings.

Specific growth rate (SGR) (% per day)
The average values of specific growth rate of Vietnamese koi were observed as 2.590%, 2.560% and 2.598% in treatments T1, T2 and T3, respectively.There was no significant difference (P<0.01)among the different treatments.Islam (2007), Begum (2009)

Survival rate (%)
The highest survivability was recorded in T1 (87%) and the lowest survivability was in T3 (69%).There was significant difference (P<0.01)among the different treatments.Variation in stocking density of fish may change growth and survival rates.According to Kohinoor et al. (2007) survival rate of monosex tilapia were varied from 79% to 92%.Survival rate was found to be negatively influenced by different stocking densities such as the lowest stocking density showed the highest survivability.It might be due to high competition for food and space among the fishes.

Production (Kg/dec/90days)
The highest production was observed to be 25Kg/dec/90 days in treatment T3 and the lowest production was observed to be 18 Kg/dec/90days in treatment T1.Although the mean weight gain in treatment T1 was highest but total production was highest in treatment T3 which might be due to higher stocking densities.Begum (2009) observed the highest production was 14.63 kg/dec/120 days which is much higher to our present findings.The present result also supports the findings of Haque (2014) and Hasan (2007) who achieved the higher production from higher stocking densities compared to that achieved with the lower ones.

Benefit-cost analysis
From this experiment, it was found that the highest net profit was BDT 32,690in T1 followed by BDT 36,104 in T2 and BDT 38,450 in T3.That time the market price was BDT 130/kg fish.Culture of Vietnamese koi at stocking density (150 fish/dec) showed higher benefit in short period of time.The benefit cost ratio was 1.7, 1.63 and 1.56 in T1, T2 and T3, respectively.Alim (2013) stated that the benefit-cost ratio was 1.35, 1.52 and 1.30 in T1, T2 and T3, respectively which is lower than our present findings.So it can be concluded that the benefit-cost ratio (BCR) in T1 was more beneficial than T2and T3.

Summary and Conclusion
An investigation on "Impact of stocking density on the growth and production of Vietnamese koi at stocking density over a period of 90 days from 1 th September 2014 to 30 th November 2014 in farm pond of Noha Aqua Farm at Muktagacha region of Mymensingh.Three treatments such as T1, T2 and T3 each having two replications which were chosen randomly and Vietnamese koi fry were stocked as 150 fish/dec (T1), 250 fish/dec (T2) and 350 fish/dec (T3) respectively.Fishes were fed on commercial feed.The initial average weight of the fingerlings were 1.0 g.Variation of water quality parameters were observed among the different treatments and all the values were within the acceptable and suitable range for Vietnamese koi culture.Under the experimental condition, different treatments showed different growth rates.From the present experiment, it was found that the total production was increased with the increase of stocking density.But the individual fish growth rate was decreased with the increase of stocking density.From this experiment, it was found that the highest net profit was BDT 32,690in T1 followed by BDT 36,104 in T2 and BDT 38,450 in T3.That time the market price was BDT 130/kg fish.Culture of Vietnamese koi at stocking density (150 fish/dec) showed higher benefit in short period of time.The benefit cost ratio was 1.7, 1.63 and 1.56 in T1, T2 and T3, respectively.Present findings indicated that comparatively highest individual weight gain was found in treatment T1 which received lower stocking density (125 fish/dec).Water quality parameters were found within suitable range.From the experiment it might be suggested that the stocking density (150 fish/decimal) performed the better results and further study is needed to explore the economics of Vietnamese koi farming with different stocking densities.
(a) Mean weight gain (g) = Final weight-Initial weight (b) The survival rate was estimated by the following formula: Survival rate (%) = No. of stocked fishes No.of harvested fishes  100 (c) Specific growth rate (SGR % per day) was estimated by the following formula: SGR (% per day) = Loge W2-Loge W1 T2-T1  100 Where, W1 = Initial live body weight (g) at time T1 (day).W2 = Final live body weight (g) at time T2 (day).(d) Food conversion ratio (FCR) = Feed fed (dry matter) Live weight gain

Table 1 .
Research layout of Vietnamese koi monoculture