XINING - Northwest China's Qinghai province plans to release seven million of a rare fish species into China's largest lake before the end of the year, to boost fish stocks, local authorities said Wednesday.

Qinghai will release six million naked carp, only living in Qinghai Lake and its basin, into Qinghai Lake, a saltwater lake, the provincial agriculture and husbandry bureau said in a press release.

Authorities released one million naked carp into the lake in the first half of the year.

The slow-growing fish is critical to the "water-fish-bird" ecosystem in Qinghai Lake. It is under second-class state protection.

Qinghai Lake is dubbed the gene database for highland species.

Fish catches in the lake declined sharply due to over-fishing - from 320,000 tons in the 1970s to less than 1,000 tons in the 1980s.

Dam building and the drying up of some rivers in the highland region destroyed some of the fish's breeding bases, as the fish need to travel upstream to lay eggs in the summer.

Qinghai banned fishing in 1980s and then started releasing naked carp into Qinghai Lake to boost fish stocks.