A $2.5 million worth deep-sea farming platform, where 200,000 croakers are raised inside, looms in the water near Lianjiang county. By HUMEIDONG/CHINA DAILY

As coastal waters are already clogged with fish farms, fishing companies like Fujian Xinmao are turning their eyes to areas farther offshore, where waters can be as deep as 30 meters.

Lu, who used to work in the shipbuilding industry, said the advance toward deeper waters was made possible by engineering advancements that can create controlled environments for fish cultivation in the open ocean.

"Building the platform is much more complicated than building a ship because it must be engineered to be strong enough to withstand extreme weather," he said.

Lu, who quit shipbuilding to develop the platform in 2003, said the company had reached out to several design teams, but found no success until they talked to a team from the Wuhan University of Technology in Hubei province.

A design was rolled out in 2020, leading to the platform's debut in July 2021.

It was put into use amid a nationwide campaign to build "blue grain barn" to meet the nation's growing need for food, and as authorities began racing to phase out aquatic farms close to shores that clog up shipping lanes and damage the ecological health of mangroves.

Lin Yinghui, an official with the county's ocean and fishery bureau, said traditional aquaculture creates problems such as feed pollution and eutrophication, which in turn affects the quality of aquatic products and even causes red tides that can wipe out yields.