The first quarter of 2013 saw 12 RIA M&As. Activity peaked in the first quarter of 2015, at 39 deals. All told, 471 deals have been inked since the beginning of 2013.

DeVoe's research shows that RIAs of all sizes are weighing sales and merger opportunities across the country, as "operational fatigue" in managing regulatory issues is motivating interest, particularly among smaller firms.

So-called established RIAs, with $100 million to $250 million in assets under management, accounted for half of the deals in the first quarter this year.

Breakaway advisors—those leaving wire houses for an RIA firm–accounted for the other half.

The average AUM for selling firms was about $600 million in the first quarter, down from an average of $1 billion in 2016. DeVoe says the average dropped due to the number of smaller selling firms.

Regional banks have stepped up their acquisitions of late, accounting for 16 percent of the recent purchases. "These regional banks are likely pursuing cross-sell strategies and are attracted to the deep client relationships RIAs have with their high-net-worth clients," DeVoe's report says.

More than half the deals in the first quarter were consolidations—and not full firm sales. Only 18 percent of the deals were larger RIA firms buying smaller RIA firms.

Would fiduciary rule accelerate RIA M&A activity?

As of May 2015, there were 32,736 RIA firms, according to Meridian-IQ, which was acquired by DiscoveryData in 2016, a provider of analytics to the financial services industry.

DeVoe's research does not predict the continued pace of sales or consolidations. While it makes reference to the weight of regulatory burdens on sellers' decisions, it does not mention the Labor Department's fiduciary rule.

Much of the years-long debate over the merits and risks of the fiduciary rule has focused on its impact on the broker model, and price compression among asset managers, which have been under pressure from record flows to passively managed mutual funds—a trend that is expected to accelerate under the fiduciary rule.

As the rule is currently written, it is bound to impact the RIA fee-based advisory model as well, says Chris Jones, chief investment officer of Financial Engines, the country's largest independent RIA.

"Advisory models are already under some price pressure," Jones told BenefitsPRO, citing the impact of fiduciary robo-advisories.

Moreover, traditional RIAs that offer committed client relationships have an "inherently high" cost structure to their business models, said Jones.

"Most RIA shops are small. Even if you are charging a 1 percent fee, the cost of customer acquisition is high. It's going to be challenging for traditional advice providers to lower their costs," he said.

Under the fiduciary rule, discount brokerages with considerable scale would be required to operate as fiduciaries on qualified retirement accounts. That would dramatically reshape the competitive playing field for traditional RIAs.

"The world is changing quickly," said Jones. "Consumers will be less willing to pay high prices for personalized advice. You are going to have respond to that if you are a traditional RIA."

Related: See more BenefitsPRO fiduciary rule coverage