Stelmar Being Acquired for \$677 Million  NEW YORK (Reuters) - Private equity firm Fortress  Investment Group LLC has agreed to buy oil tank operator  Stelmar Shipping Ltd. &lt;A HREF="http://www.investor.reuters.com/FullQuote.aspx?ticker=SJH.N target=/stocks/quickinfo/fullquote"&gt;SJH.N&lt;/A&gt; for \$677 million, Stelmar said on  Monday.