Charles Hepworth, investment director in charge of the DFM proposition at GAM, is selling his stake in Standard Life Investments' Global Absolute Return Strategies (GARS) fund on size concerns.
Shares in oil giant BP shot higher this morning, lifting the wider market, after the group pleased investors by raising its dividend.
Buyers fear increased stock-specific risk as active EM funds run high weightings to developed markets.
Aviva and Aberdeen Asset Management sat atop the FTSE 100 leaderboard on Thursday morning but the wider market remained subdued.
Aviva has completed the sale of its US life and annuities business for £500m more than it originally announced.
Shares in asset managers Schroders and Henderson have fallen in morning trading while Aviva climbed following a set of half-year results from the groups.
Aviva has reported a profit after tax of £776m for the first half of this year, turning around a £624m loss for the half year 2012, but said its funds business has seen outflows.