Introduction:

Vietnamese koi which is originated from Vietnam is gaining attention to farmers at an increasing rate in South Asian countries. Vietnamese koi strain has been introduced in Bangladesh in 2010 (Ahamed et. al. 2018; Ahmed et. al. 2014). The fish grows very fast and it is also market-demanded fish in local market in Bangladesh. On other hand, monosex tilapia is also popular fish species in Bangladesh as the fish can grow fast, live in high stocking densities and consume natural food in pond (Begum et. al. 2017).

Although polyculture of different fish species is practiced in Bangladesh, polyculture of Vietnamese Koi and monosex tilapia is not available seen here. But, there has much potentiality and feasibility of polyculture of these fish species. In this document, we will observe the polyculture method of Vietnamese Koi and monosex tilapia in pond and its advantages and disadvantages to farmers:

Pond selection:

30 decimals – several acres land can be selected as pond for the polyculture of Vietnamese koi & monosex tilapia (Faruk et. al. 2018). Clayey-loam soil is best for the earthen type pond to culture fish. Edges of the pond should be minimum 3 feet high (FAO Fisheries and Aquaculture) otherwise koi fish can be climbing from the pond in Rainy season.

Manuring:

Inorganic fertilizers such as Urea and TSP can be scattered to the pond when there is lacking plankton in the pond. Urea 200 gm/decimal and TSP 100 gm/decimal can be used in the pond if the water depth is minimum 5 feet (Fish- Blue Gold Program, 2022). Excess amount of manuring can create plankton bloom in pond and create gas which is toxic to fish.

Water quality control:

Suitable water condition for Vietnamese koi and monosex tilapia are: temperature = 20 – 30°C, O2 = 6 – 7 ppm, pH: 6 – 8.0, transparency = 30 – 40 cm, NH3 = less than 0.01 mg/L (Faruk et. al. 2018).

Water quality parameters should be checked weekly by test kits. Aerator and Oxygen tablet can be used if oxygen becomes short in the pond water. A net or a bamboo can also be used to blow the pond water to improve oxygen content in water. Lime 500 gm/ decimal can be used if pH imbalance is found in pond water (FAO Fisheries and Aquaculture). Turbidity and gas formation in the pond can be reduced by exchanging water or freshwater supply daily. Feeding should be stopped for two days if O2 shortness and turbidity occur in pond (FAO Fisheries and Aquaculture).

Fry selection and stocking:

Fry should be collected from a reliable hatchery. Quality of fry is utmost important to get a good production from the culture. Fry should be checked by a Fisheries Specialist during purchase the fry from the hatchery. Minimum 06 hours of conditioning of the fry is important before packing the fry (Alikunhi, 1957). Fry size average 2 – 3 gm and 300 – 350 pieces/ decimal mixed fry of koi and tilapia can be stocked in the pond for commercial fish culture (Halim et. al. 2017). Koi and tilapia fry stocking ratio can be 2:1 per decimal (Jahan et. al. 2013). March- April (Rainy season) is suitable season to start the culture.

Feeding:

A commercial feed can be fed to the fish daily (at morning and afternoon). Protein content of the feed should be minimum 30% as koi fish need higher protein content in their feed for the better growth (K. Bashir et. al. 2010). Feeding to the fish should be according to the body size of the fish (about 8% during nursery, 5% during juvenile and 2-3 % during grow-out stage of the fish) (Bashir et. al. 2010).

Sampling of fish:

Weight of fish should be recorded fortnightly. 5 -10 pieces of fish can be sampled to get the average weight and length of fish (Hansen et. al. 2007).

Disease management:

Disease can be occurred during the culture period. Cloudy weather, oxygen shortness, overfeeding, injury to fish etc. can create disease in fish. Bacterial diseases are commonly found in koi and tilapia fish. Oxytetracycline about 75 mg per kg fish for ten days can be used to cure the disease (Drugs.com, 2022). Besides, water quality should be improved to minimize the problem. Infected and dead fish should be removed from the pond immediately. Biosecurity measures should be followed strictly to maintain the good water environment in pond.

Harvesting of fish:

Vietnamese koi normally becomes 300 – 350 gm within four months culture period (Ahmed et. al. 2014) and monosex tilapia becomes 400 – 500 gm within four months culture period (Felix et. al. 2021). Vietnamese koi can be harvested and marketed just after four months of culture.

Production:

Fish production amount from a successful polyculture for four months can be: Vietnamese koi around 12000 kg/hectare and monosex tilapia around 9000 kg/hectare (Felix et. al. 2021; Ahmed et. al. 2014).

Benefits and drawbacks of polyculture of Vietnamese koi and monosex tilapia:

1. Fast growth and high yielding fish species
2. Both fish species can be cultured at high stocking densities
3. Well tolerate fish species in fluctuate water condition
4. Both fish species can eat same feed
5. Both fish species can eat plankton, so pressure reduce on supplementary feed amount
6. Vietnamese koi gets faster growth and body weight than local koi
7. Growth rate of both fish species is near to same
8. Both fish species can be marketed just after four months culture period
9. Both fish species are popular and market-demanded in Bangladesh

High feed cost, infected fry from the source, breeding of tilapia due to improper hormonized monosex tilapia, sudden low price of tilapia at market are some drawbacks in the polyculture.

References: 

1. Alikunhi KH (1957) Fish Bull, Indian Coun. Agric. Res. 20, 144.
2. Ahmed GU, Upala SR, Hasan MT and Hasan NA (2014) Comparative study on growth  
3. performance between Vietnam koi and Thai koi in mini ponds, J. Bangladesh Agril.  
4. Univ., 12(2): 405–409.
5. Ahamed S, Hasan KR, Mou MH and Mursalin MI (2018) Polyculture of Vietnamese koi (Anabas testudineus): Emphasis on Seasonal Mini Water Ponds in Semi- Arid Zone of Bangladesh, Annual Research and review in Biology, 27 (6): 1- 7.
6. Bashir K, Patil S and Ganai AM (2010) Effect of formulated feeds with different protein levels on performance of koi carp (Cyprinus carpio var. koi), Animal Nutrition and Feed Technology, 10 (2): 195 – 200.  
7. Begum N, Islam MS, Haque AKMF and Suravi IN (2017) Growth and yield of monosex tilapia (Oreochromis niloticus) in floating cages fed commercial diet supplemented with probiotics in freshwater pond, Sylhet, Bangladesh J. Zool., 45(1): 27-36.
8. Blue Gold Program (2022) Fish. http://www.bluegoldbd.org/downloads/extension materials/ffs-    messages/fish/
9. Drugs.com (2022) Terramycin 200 for Fish. https://www.drugs.com/vet/terramycin-200-for-fish.html
10. FAO Fisheries and Aquaculture (2022) Pond conditioning through liming, https://www.fao.org/fishery/docs/CDrom/FAO_Training/FAO_Training/General/x6709e/x6709e05.htm   
11. FAO Fisheries and Aquaculture (2022b) Fish pond construction chapter, https://www.fao.org/fishery/docs/CDrom/FAO_Training/FAO_Training/General/x6708e/x6708e06.htm    
12. Faruk A, Hossain A, Asif AA, Bhuiyan MNM and Sarker MJ (2018) Culture and management techniques of Vietnamese Koi, Asian- Australasian Journal of Bioscience and Biotechnology, 3 (2): 93 – 105. 
13. Felix E, Avewemoya FE and Abah A (2019) Some methods of monosex tilapia production: A review, International Journal of Fisheries and Aquatic Research, 4 (2): 42 – 49.
14. Halim MA, Nabi MM and Nahar S (2017). Study on optimization of stocking density of climbing perch (Anabas testudineus, Bloch 1972) in marginal farmer earthen ponds, Journal of Entomology and Zoological Studies, 5 (3): 833 – 837.
15. Hansen MJ, Beard TD and Hayes DB (2007) Sampling and experimental design. Pages 51–120 in C. S. Guy and M. L. Brown, editors. Analysis and interpretation of freshwater fisheries data. American Fisheries Society, Bethesda, Maryland.
16. Jahan S, Chandra KJ and Das DR (2013). Growth performance of climbing perch (Anabas testudineus) in monoculture and polyculture system. IRJALS, 2(3):1-10.

 

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