UPDATE 1-Fidelity brokerage assets up 2 pct to $1.92 trillion

(Adds details of assets, brokerage accounts)

BOSTON, July 22 (Reuters) - Fidelity Investments, the world's biggest mutual fund firm, said on Tuesday client assets at its brokerage business rose 2 percent to $1.92 trillion in the second quarter from a year ago due to new assets gathered, especially in the arm that deals with advisers.

Fidelity said in a statement the business was also helped by market conditions in the quarter, which boosted trading activity and led to the opening of new brokerage accounts.

The operational results at privately held Fidelity's brokerage business come after rivals Charles Schwab Corp (SCHW.O) and TD Ameritrade Holding Corp (AMTD.O) posted stronger-than-expected results last week.

Fidelity added $23.5 billion in net new client assets in the quarter for the brokerage business. Fidelity Institutional Wealth Services, which provides services to advisers and third-party administrators, saw quarterly net new client assets rise by 10 percent against the prior period, the firm said.

But net new client assets, which include sales of Fidelity and non-Fidelity mutual funds and individual securities, dropped from $41.3 billion in the first quarter of 2008. They were also lower than the $31.2 billion of net new client assets added in the second quarter of 2007.

Daily average commissionable trades rose 19 percent to 416,085 and the firm added 130,000 new brokerage accounts, bringing total number of accounts to 18.1 million, it said.

Boston-based Fidelity's investment management business has $1.5 trillion in assets. (Reporting by Muralikumar Anantharaman; Editing by Brian Moss)