BOSTON, Oct 31 (Reuters) - Billionaire investor David Einhorn's hedge fund Greenlight Capital posted a small gain in October when stocks tumbled but is still nursing some of the industry's biggest losses for the year, an investor said on Wednesday.

Greenlight Capital told investors late on Wednesday that its fund gained 1 percent in October and is down 25 percent for the first 10 months of 2018. A spokesman for the fund declined to comment. (Reporting by Svea Herbst-Bayliss; Editing by Chris Reese)