'Blue grain barn'

The platform was put into use amid China's "blue grain barn" campaign to meet the nation's growing food requirements.

These platforms are now favored by authorities seeking to phase out nearshore aquaculture, which obstructs shipping lanes and harms the ecological balance of mangroves.

China outlined its ambition to build "modern sea farms" like those in Lianjiang, in the No 1 Central Document last year, an important annual policy statement.

In June, six government departments, led by the agriculture ministry, issued guidelines to accelerate deep-sea farm construction and enhance research on cages and the smart equipment necessary for their operation.

The latest No 1 Central Document, released in February, reiterated support for deep-sea aquaculture, urging local officials to maintain a "macro food perspective".

Lin Yinghui, an official with the Ocean and Fishery Bureau in Lianjiang, said traditional aquaculture, where fish are raised in smaller cages nearer to the shore, creates problems such as feed pollution and eutrophication, a process in which surplus nutrients cause dense plant growth, and is not sustainable.

Environmental degradation has affected the quality of aquatic products and even caused red tides that can wipe out yields.

Lin said in recent years Lianjiang county has promoted ecological aquaculture platforms, so fish farming operations can be gradually shifted farther from shore.