Viking Global's longtime head of trading is stepping down from the $55 billion asset manager

Andreas Halvorsen runs $55 billion Viking Global.

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• Stuart Brown is stepping down as head of trading at $55 billion hedge fund Viking Global.
• Brown has worked at the hedge fund for 18 years, according to his profile on the firm's website.
• The hedge fund was up only 8.6%, trailing the market and many Tiger Cub peers.

Billionaire Andreas Halvorsen will soon lose another longtime lieutenant.

Stuart Brown, the longtime head of trading for Viking Global...