China launched a fishery resources survey along the Yellow River, the country's second largest, on Friday, fishery authorities said.

This is the first survey of inland waters since the last survey of nationwide fishery resources in the 1980s, according to officials of the Huanghai and Bohai Fishery Bureau under the Ministry of Agriculture in the coastal city of Yantai in eastern Shandong Province.

The fishery researchers will seek to understand the changes in fishing resources over the past 30 years and learn of existing fish species and their current living situations.

The researchers will also inspect alien fish species found in the river, in the survey that is expected to be finished within the year.

According to survey data from the 1980s, there were 191 fish species living in the Yellow River valley.

Species of fish in the river, however, have declined over the past three decades because of building dams and water diversion projects, as well as unhealthy aquaculture activities, while alien invasive species increased.