Bulgaria opened bidding Monday for the state-run sea shipping company.Seventy percent of Bulgarian Maritime Navigation's capital will be put up for sale to a private owner, with only investors in maritime transport activities eligible, said the director of Bulgaria's privatization agency, Teodor Nikolov.The remaining 30 percent will be offered for sale to the buyer after a period of five to six years.Bids may be submitted until Oct. 18, and negotiations with prospective investors are scheduled for the first half of 2008, Nikolov said.For a 10-year period, the owner will be barred from petitioning for liquidation or making any type of company transformation, Nikolov said.Also for 10 years, the average annual tonnage of the ships should not be less than 1.3 million gross registered tons, and at least 60 percent of the ships should sail under the Bulgarian flag.The company has 82 vessels — 77 cargo vessels and five auxiliary vessels — most of them bulk carriers. The shipping company employs more than 4,000 workers, most of them directly involved in shipping operations.