The major Wall Street banks saw their capital markets revenue decline in the second quarter, as market volatility ebbed, says a new report from New York-based Fitch Ratings.

The five largest global trading and universal banks saw a collective 15% drop in capital markets revenue in the second quarter of 2015, “as lower volatility outweighed continued strong advisory and M&A activity,” the credit rating agency says.

Among the big banks, Morgan Stanley made the largest gain in revenue share during the quarter, Fitch reports, due to strong underwriting and equity capital markets performance. However, JP Morgan, Goldman Sachs, and Citi remained ranked as first, second and third, respectively, in terms of their share of revenue.

“Overall, revenues during the second quarter were bolstered by advisory and equity markets,” says Justin Fuller, senior director, financial institutions, at Fitch, in a statement. “Fixed Income, Currency and Commodities is still a significant part of the revenue picture, but remains pressured by lower volatilities in foreign exchange and rates.”

Subdued volatility “has the potential to continue to impact banks’ capital market activities” in the months ahead; with their FICC businesses “potentially grabbing a smaller-than-usual slice of the pie if it continues,” Fitch Ratings says.

Still, the credit rating agency expects the advisory business to remain a bright spot through the end of 2015, although the pace of M&A activity may slow beyond the end of the year, Fitch Ratings notes.

A rise in short-term interest rates by the U.S. Federal Reserve would have a mixed impact, Fitch Ratings says, “as the rates business is likely to improve, offsetting potential declines in credit and mortgages.”