Cage fish farming: how the Dakatia model raises monosex tilapia in rivers

Cage fish farming is the raising of fish commercially at high density in floating cages set in rivers or other large water bodies. According to an article in Krishi Kotha, the magazine of the Agriculture Information Service (AIS), published in January 2018, the practice began on China's Yangtze river about 750 years ago. In Bangladesh it became best known through the experience of the Dakatia river in Chandpur, known as the "Dakatia model". This April 2025 report sets out its history and main rules.

Teaching notes by Professor Md Akhtar Hossain of Rajshahi University's Department of Fisheries say cages were first tried in Bangladesh at Bangladesh Agricultural University in the late 1970s. The Department of Fisheries ran a cage culture project in Kaptai lake in 1985-86, and CARE and DFID ran the CAGES project for landless poor people from the end of 1995 until 2000.

Large-scale commercial farming began in 2002. Since then monosex tilapia have been farmed in cages on the Dakatia river in Chandpur district and on the Rahmatkhali channel of the Meghna in Lakshmipur district. Wikipedia records that the method was modelled on practice in Thailand. According to the AIS article, within six years about a thousand cages of monosex tilapia were being farmed at the two sites, producing about 700 tonnes of exportable tilapia a year; the commercial success on the Dakatia gave the system its name.

The Dakatia flows from the hills of Tripura in India through Cumilla and Chandpur districts and joins the Meghna near the Boro Station molehead at Chandpur. The AIS article records that in 2010 a project in Derai upazila of Sunamganj began with 18 cages on the Surma river and grew to 70 cages in two upazilas, benefiting 148 families. A Prothom Alo report of September 2015 described monosex tilapia being raised in cages on the Dudhkumar and Brahmaputra rivers in Kurigram.

Because river water keeps flowing, the water inside a cage is constantly replaced, so fish can be kept at a higher density than in a pond. The Rajshahi notes add that cages are relatively cheap, quick to assemble, movable, need little land and no separate water supply, and can serve poor people with no pond or field.

For choosing a site, the notes list four points:

• a suitable current in the river, ideally 4 to 8 inches per second;
• a spot close to the village, for security;
• water free of pollution;
• easy transport for taking fish to market.

The Dakatia model usually uses cages of two sizes: 20 ft x 10 ft x 6 ft and 10 ft x 10 ft x 6 ft. The Rajshahi University notes likewise give the size of a floating river cage as 6 m x 3 m x 2 m or 3 m x 3 m x 2 m. The frame is made of GI pipe, floated on 200-litre drums and held firmly in place in the river with anchors. The net must be one that crabs cannot cut, since net-cutting by crabs is a known problem in cage farming.

Stocking density depends on the species, production target, water depth and current, mesh size and feed. According to Professor Akhtar Hossain's notes, 30 to 40 fish per cubic metre can be stocked for feed-based monosex tilapia farming in river cages, with an initial stocking weight of 25 to 30 grams.

In flowing water the feed has to be floating pellets, so that it stays in the cage and is not lost through the mesh. Tilapia feed should contain 28 to 30 per cent protein. Farmers should ask the upazila fisheries officer how much feed to give each day for the weight of their fish, when to grade them and what to do if disease appears. A cage can produce two to three crops a year.

The Rajshahi notes also list problems reported around the country: a lack of quality fry, no low-cost supplementary feed, cages too far from home to look after, fish escaping in floods, crabs cutting nets, poor water quality from jute retting, storms, deaths from disease and parasites, poaching and poisoning.

Photo: AsikBinRahim / Wikimedia Commons (CC BY-SA 4.0)

Sources: The Agro News (Online Desk), Agriculture Information Service (Krishi Kotha, January 2018), Department of Fisheries, Rajshahi University (teaching notes by Professor Md Akhtar Hossain), Prothom Alo (30 September 2015), Wikipedia (cage fish farming, Dakatia River, Nile tilapia)