Coral fish farming sees success in sea-based floating cages

Bhetki, also known as coral fish, is gaining popularity among consumers and fish farmers alike due to its exceptional nutritional value, delicious taste, and high market price. One of its key advantages is its low spine count, which makes it more appealing both locally and internationally. In Bangladesh, this premium fish is commonly known by two names—Bhetki and Coral.

Researchers at Bangladesh Agricultural University (BAU) have recently introduced an innovative method for farming Bhetki in floating sea cages. Using a specially formulated supplementary feed developed in BAU’s laboratory, they have successfully cultivated Bhetki in a controlled environment. This approach not only enhances the protein content in the fish but also significantly increases profits. Experts believe this method has the potential to transform the livelihoods of people living in the coastal Sundarbans by creating sustainable employment opportunities.

Growing Demand Amid Declining Supply
The bustling fish market in Mymensingh has seen a surge in attention toward Bhetki. This sleek, silver-gray marine fish with vibrant eyes and a streamlined body has become a prized catch. However, vendors attribute its rising price to a sharp decline in availability. Factors like reduced river navigability, pollution, overfishing using current nets, and the disruption of natural river estuaries have all contributed to this scarcity.

Groundbreaking Research and Field Trials
This breakthrough in Bhetki farming is the result of research led by Professor Dr Md Shahjahan from BAU’s Department of Fisheries Management, with Jabed Hasan, a postgraduate student, as his associate researcher. The fieldwork for this study was conducted in three key coastal areas—Munshiganj in Satkhira, Maheshkhali in Cox’s Bazar, and Char Kukri-Mukri in Bhola—under the Sustainable Coastal Marine Fisheries Project (SCMFP), funded by the World Bank and overseen by the Department of Fisheries.

Eco-Friendly and Disease-Free Farming
One of the key advantages of this cage farming method is the health of the fish. As the fish are gradually introduced to supplementary feed in a flowing river environment, there have been no reports of disease. The natural water current helps flush away waste and uneaten food, preventing water pollution. Interestingly, this even promotes algae growth, which further balances the aquatic ecosystem.

A Species Suited for Dual Environments
Scientifically known as 'Lates calcarifer', Bhetki belongs to the Centropomidae family. It is a fast-growing, carnivorous species capable of thriving in both freshwater and saltwater. During its juvenile phase, it lives in freshwater, migrating to the sea as it reaches sexual maturity. This adaptability makes it suitable for cultivation in diverse aquatic conditions. Rich in omega-3 and omega-6 fatty acids, along with essential vitamins A, B, D and minerals such as calcium, iron, zinc, potassium, magnesium, and selenium, Bhetki offers a wide range of health benefits—from boosting immunity and heart health to muscle development and hormone production.

Comparative Studies and Results
To test the effectiveness of different feeding methods, researchers used two types of fry: hatchery-bred and river-collected. The hatchery fry were fed commercial feed containing 40–52% protein, while the river fry were fed a specially prepared 37% protein feed developed by BAU. Both groups were reared in 60-cubic-meter circular cages, each 6.7 meters in diameter. While the hatchery fry yielded 13–14 kg of fish per cubic meter, the river fry achieved a higher yield of 17.5 kg per cubic meter. This meant each cage could produce around 1,050 kg of fish—far exceeding the 600–1,500 kg per hectare typical of traditional pond farming. Moreover, the protein content in cage-farmed fish reached 19%, compared to 17% in pond-farmed fish.

Cost-Effective Feeding Strategy
The method of gradually accustoming the fish to new food was also carefully structured. For the first three months, the fish were fed small pieces of tilapia, sized to fit their mouths. Over the next three months, they received a 50-50 mix of tilapia and commercial feed. In the final stage, the fish were switched entirely to the BAU-developed feed. Remarkably, the growth rate remained consistent throughout the transition, while the cost of the lab-made feed was significantly lower—boosting overall profitability.

Addressing Farming Challenges
Despite its potential, Bhetki farming has certain limitations. When fry are collected from the sea, it’s essential to ensure they are of uniform size to prevent cannibalism. Recently, Greenhouse Mariculture in Cox’s Bazar has begun commercial-scale production of Bhetki. While constructing durable plastic cages involves some upfront investment, they can last up to ten years. For those with limited resources, cost-effective alternatives made of bamboo or cane are also viable.

Unlocking National and Global Potential
Jabed Hasan pointed out that while Bangladesh’s fish production has grown sixfold over the last 30 years, driven largely by aquaculture, there has been little advancement in utilising natural water bodies like rivers for farming. In contrast, neighbouring countries—especially China—have made significant progress in this area. Embracing modern, sustainable methods of fish farming is essential for Bangladesh to meet rising domestic meat demand and stay competitive globally.

Nutritional and Economic Impact
Bhetki is not only a nutritional powerhouse, but also a promising contributor to the economy. With its high-quality meat, rich in omega fatty acids and essential nutrients, it supports immune function, heart health, muscle growth, and overall well-being. From a broader perspective, coral fish farming offers great potential for job creation, foreign currency earnings through exports, and enhancing national food security.

High Reproduction and Farming Potential
Bhetki also stands out for its high reproductive capacity, producing 6–7 million eggs per year. It is fast-moving, highly tolerant to salinity, and can be farmed in freshwater, semi-saline, and saline environments—making vast areas of Bangladesh’s coastal regions suitable for its cultivation. With growing domestic and international demand, the prospects for expanding Bhetki production and exports are brighter than ever.