There were 109 mergers and/or acquisitions last year involving registered investment advisors, according to data released Wednesday.

Schwab Advisor Services., which provides custodial, operational and trading support for more than 6,000 independent registered investment advisory firms, reported that this marketed the largest number of deals in a year since Schwab began tracking deal activity in 2003 and a significant increase from the 70 deals in 2009.

The 109 transactions represented approximately $156 billion in assets under management, compared to $103 billion in assets under management a year earlier. The average transaction size was approximately $1.4 billion compared to approximately $1.5 billion in 2009.

RIA firms were the most common buyers among 2010 deals, accounting for more than 50% of acquisitions, a trend that has continued since 2007.

Of the deals tracked by Schwab, 58% represented less than $500 million in assets under management, 23% were between $500 million and $2 billion, and 19% of deals were greater than $2 billion.

“We saw a significant uptick in M&A deal activity among RIAs in 2010, largely due to advisors putting these discussions back on the front burner after spending the bulk of 2009 helping clients navigate the volatile market environment and managing the day-to-day business of their firms,” said David DeVoe, a managing director of strategic business develop at Schwab Advisor Services. “Specific drivers of deal activity include advisors’ growing interest and sophistication in M&A and succession planning, continued interest of holding companies and private equity firms in RIAs, as well as advisor principal demographics.”

Last week, Fidelity Investments reported it helped 146 individual brokers and teams managing $12 billion in assets transition to a range of independent business models last year. Of this group, nearly 45% started either a registered investment advisory firm or an independent broker-dealer, while the remaining 55% joined an existing RIA or broker-dealer on Fidelity’s platform.