VESSEL REVIEW | Zhannong No 1 – Chinese firm to deploy semi-submersible fish pen off Guangdong province

Construction was recently completed on a new offshore aquaculture structure that will be installed in the South China Sea just off China's Guangdong province.

Zhannong No 1 (湛农1号) consists of three sets of rectangular modules having a total of six 60- by 30-metre (200- by 100-foot) fish cages that can be raised and submerged individually.

Durable harvesting platform designed to withstand challenging offshore conditions

The platform is a reef-type bottom truss structure, and the cages can be submerged five meters (16 feet) below sea level. This allows the structure to safely harvest fish even as the area in which it is deployed is subjected to 17 typhoons and other extreme conditions over a period of one year, whereas traditional structures fitted with gravity cages can be deployed only within a limited weather window.

The aquaculture structure itself has an LOA of 95 metres (310 feet), a beam of 30 metres (100 feet), a depth of 12 metres (39 feet), and a height of 48 metres (160 feet), while the six cages can store up to 62,000 cubic metres (2.2 million cubic feet) of seawater when submerged. The cages are built with a double-layer net structure to protect against impact damage.

Automated systems to permit operation without embarked personnel

After the cages have been put into operation, and after being relocated as necessary, the structure can harvest up to 900 tonnes of fish of different species and sizes each year. This translates into annual revenues in excess of CNY20 million (US$2.8 million).

Intelligent breeding systems and automated feeding, net washing, and independent cage lifting systems are fitted so that the structure can operate continuously even without an embarked crew. Electrical power for all onboard systems will be supplied via PV panels, allowing the structure to conduct harvesting and feeding without any adverse impact on the surrounding marine environment.

More economical alternative to traditional harvesting platforms

Zhannong No 1, which was designed to have a service life of 20 years, will be operated by China Communications Construction Company (CCCC) via its CCCC Guangzhou Navigation Bureau division. The structure was built by the Zhanjiang Agricultural Development Group.

Guo Qi, Deputy General Manager of CCCC Guangzhou Navigation Bureau, said that Zhannong No 1 had a total construction cost around 40 per cent lower than that of a traditional semi-submersible aquaculture structure, thus allowing a greater number of such structures to be manufactured and deployed in China’s offshore waters.

Among the species that Zhannong No 1 will initially harvest off Guangdong are cobia, golden pomfret, octopus, and black catfish.