Vanguard on Friday said its chief investment officer Gus Sauter plans to retire at the end of 2012. The 25-year Vanguard veteran is known as a pioneer in passively managed index funds and ETFs.

He will be replaced as CIO by Vanguard insider Tim Buckley, 43, who has directed the firm’s retail investor group since 2006.

Sauter, 57, joined Vanguard in October 1987, just two weeks before the Black Monday crash.

At Vanguard, the investment management groups he oversees are responsible for $1.6 trillion in assets, according to a press release.