It is recorded in Wu Lu written by Zhang Bo in the Jin Dynasty (AD 266-420) that, "Zhanghai of Jiaozhou Prefecture produces corals which are harvested with iron nets." Fishermen back then fished for corals with iron nets. Jiaozhou was the name of an administrative division from the Eastern Han Dynasty to the Three Kingdoms Period, roughly covering Guangdong, Guangxi and Hainan of present-day China and north Vietnam.