China has completed a survey of fishery resources in the middle and southern regions of the South China Sea after two years of research, said a Chinese expert on Monday.

The survey showed the area around the Nansha Islands has fishery reserves of about 1.8 million tonnes, with about half a million tonnes available for fishing, said Yang Beisheng, deputy head of the South China Sea Fisheries Research Institute under the Chinese Academy of Fishery Sciences.

More than 20 fish species in the Nansha Islands maritime area are rare or have a high economic value, according to the investigation.

Mesopelagic fishery reserves in the waters around the Zhongsha and Xisha Islands stand between 73 million and 172 million tonnes.

The institute has carried out eight survey trips to the South China Sea using the country's first domestically produced advanced maritime fishery survey ship, the Nan Feng, since 2013.