Welder Zhang fires up his blow torch and looks up at the towering, 8,800-tonnes oil tanker that is likely to be his last job at China's privately owned Qiligang Shipbuilding Co.

Barring a miracle, the 50-year-old will soon join the thousands of unemployed shipbuilders who have fallen victim to the end of China's maritime boom and the long-awaited consolidation of its more than 1,600 shipbuilding companies.

Four years into one of the worst downturns to afflict the global shipping industry, hundreds of small to mid-sized shipyards are teetering on the brink of bankruptcy as foreign orders dwindle and domestic lenders slash credit.

"The building of this ship is almost done, and we don't expect to have any new jobs soon," said Zhang, who asked to be identified by one name.

"We used to work 30 days a month, but now we work only 10 to 20 days because not many ships are being built. Many workers have moved on to other jobs."

Qiligang Shipbuilding is one of several troubled firms in the eastern coastal Zhejiang province, the world's largest manufacturing base for small to medium-sized dry docks.

According to local media, around 80 percent of shipyards in Zhejiang have either suspended production or are operating at half their capacity.

"The grass is growing high in many yards that have closed due to a lack of orders," said Zhang Shouguo, secretary general of industry group the China Shipowners' Association.

"This is just the beginning of the woes for shipbuilders and the worst has yet to come."

To survive and keep some of the sector's 400,000 workers employed, shipyards must turn to less lucrative businesses such as leasing vessels, real estate or, in the worst case, tearing apart the ships they once used to build, industry experts say.

"Shipbuilding is a very cyclical industry and those who can maintain strength, complete structural restructuring and transform will be a major force after the recovery," said Zhang Yao, spokesman for Singapore-listed Yangzijiang Shipbuilding ( YAZG.SI), one of China's largest vessel building firms.

"For others without flexibility to deal with the market changes, dormancy may be their best choice. Eventually more than 30 percent of existing shipbuilders will disappear."

His forecast is relatively optimistic compared to the view of other industry officials. The head of the government's China State Shipbuilding Corporation, Tan Zuojun, told local media in February he believed 50 percent of domestic shipyards would go bankrupt in the next two to three years.