Image source: AMG.The first quarter was a rocky one for the stock market, and investment management firm Affiliated Managers Group (NYSE: AMG) had to do its best to weather the storm and position itself to ride out ongoing volatility. Investors were already nervous about the potential impact of the stock market's correction in January and February on the company, and coming into Affiliated Managers Group's first-quarter financial report, shareholders were prepared for a drop in revenue and flat earnings from year-ago levels.