A couple of large GSE investors apparently went bottom fishing during the first quarter of 2005, as daunting news about unfavorable legislation pushed share prices far below their year-end 2004 levels. According to data tracked by Inside The GSE, the top 10 institutional holders of Fannie Mae stock held 46 percent of outstanding shares as of March 31. That compared to 53 percent on the first trading day of the year. But some of the…