An investor pushing to have Barnwell Industries Inc. break up its assets and sell off Big Island land has lowered its ownership stake to 16.3 percent of the Honolulu-based company's shares from 19.2 percent it held last month.

Mercury Real Estate Advisors LLC of Greenwich Connecticut now owns 1.33 million of Barnwell's shares that it paid $28.8 million for, according to a statement filed Wednesday at the U.S. Securities and Exchange Commission.

Prior filings indicated the investor and related entities held 1.57 million shares.

Mercury has been the largest shareholder in Barnwell, which owns land in Hawai'i and has an oil and gas business in Canada.

On Wednesday, officials from Mercury sent a letter to Barnwell's board asking that it consider alternatives for the company, including a sale of 1,000 acres of Big Island land and share buyback.

In the letter, Mercury argued that Barnwell is an undervalued company because of its diverse operations and high administrative expenses including executive pay.

Barnwell's shares rose 21 cents to $21.56 yesterday after surging $2.36 the day before.