OMAHA, Neb. (AP) — TD Ameritrade (AMTD) said Tuesday that its fiscal first-quarter net income grew 5% and its revenue was almost unchanged as the online brokerage’s trading activity slowed amid worries about the economy.

The Omaha-based company, who’s fiscal year begins in October, posted $152 million in net income, or about 27 cents per share, in the October-December quarter. That’s up from $145 million, or 25 cents per share, in the same quarter in 2010, and topped the 26 cents per share profit that analysts surveyed by FactSet were expecting.

But revenue fell less than 1% to $653.4 million from $656.2 million. Analysts expected revenue to grow to $671.5 million. One of the key drivers of Ameritrade’s revenue is the fees it charges for transactions it handles, but trading slipped during the last three months of 2011 due to growing worries about the European debt crisis.

The average number of trades per day dipped to 367,479 from 371,916 in the same period a year earlier. In the July-September quarter, there was an average of 415,739 trades per day. And average commissions and transaction fees per trade fell to $11.90 during the quarter from $12.39 in the last three months of 2010.

“While volumes have improved over December, clients continue to hesitate in their trading and investing in the face of all of the uncertainty in the markets right now,” said Fred Tomczyk, Ameritrade’s president and CEO, during a conference call with analysts. He said that while there are signs the U.S. economy is improving, it will be a slow recovery, and there remains a “cloud of uncertainty” regarding Europe’s financial crisis.

Tomczyk said he thinks trading will improve if the situation in Europe stabilizes and the market starts to move consistently, either up or down. He said trading might also take off if the U.S. economy continues improving during the first quarter. “What’s really important is what happens in the first quarter for the U.S. economy,” Tomczyk said in an interview with The Associated Press.

Ameritrade also makes money from fees based on clients’ assets, but the current low interest rates are limiting what TD Ameritrade earns on its clients’ deposit accounts and other investment products. Ameritrade said its net new assets grew 11% to $10.2 billion from $9.7 billion. The total client assets Ameritrade holds grew 7% to $406.3 billion at the end of the quarter from $386.4 billion.

Editor’s Note: Sequentially, net new assets declined 18% in the quarter ended Dec. 30 (from $12.4 billion in the previous quarter), while total assets in the period ending Dec. 30 rose 7% from the earlier period.   

Credit Suisse analyst Howard Chen said in a research note that this was a more challenging quarter for Ameritrade, but the company is limiting expenses and managing capital well. Chen maintains a “Neutral” rating on Ameritrade’s stock because of the interest-rate pressure and slower trading outlook.

Ameritrade laid off 145 people between October and December, and severance costs totaled $7 million. But the company also benefited from a lower-than-expected tax rate, so there was a net gain of one cent per share from those two factors.

Ameritrade said it spent about $107 million during the quarter to repurchase 6.7 million shares of its own stock, and plans to pay a dividend of 6 cents per share in February.

Ameritrade’s stock declined 29 cents, or 1.8%, to $16.01 the close of trading on Tuesday.

See AdvisorOne’s Q4 earnings calendar for the financial sector.