NEW YORK (CNN/Money) - JPMorgan Chase & Co., the No. 3 U.S. bank, said its Chief Operating Officer James Dimon will succeed the current Chief Executive William Harrison on Dec. 31, six months earlier than expected.

The news came as the company posted a 78 percent jump in third quarter earnings, helped by strong trading and investment banking fees.

Speaking on the company's conference call with analysts, Harrison said "The time is right to turn leadership over to Jamie," citing success with its integration of the Bank One acquisition. He added, "We created an organization that is strategically well positioned and (Dimon) is the best person in the industry to realize and maximize this potential."

Dimon, 49, joined JPMorgan (Research) in July of last year when it bought Chicago-based Bank One Corp. which he had headed, in a $58 billion deal. The plan for him to succeed Harrison, 62, has been in place since the deal was struck in January 2004.

Piper Jaffray analyst Andrew Collins said the early change in management reflects good progress on the Bank One merger integration, and good performance in most lines of business.

The New York-based bank reported third-quarter net income of $2.5 billion, or 71 cents a share, compared with $1.42 billion, or 39 cents, a year earlier.

Excluding $221 million of charges related to its merger last year with Bank One Corp., operating earnings were 75 cents, it said. Wall Street analysts had expected the bank to earn 72 cents, according to earnings tracker Thomson First Call.

Net revenue increased 15 percent to $15.55 billion. Investment bank earnings rose 70 percent, to $1.1 billion, on record trading revenue across all areas.

The company's consumer business was weak, with operating earnings for its retail financial services business down 20 percent from last year, related in part to special provision for credit losses of $250 million attributable to Hurricane Katrina.

Overall, the quarter included a Hurricane Katrina-related credit charge of $248 million, after-tax, or 7 cents per share.

On the analyst call, Dimon said the company also experienced a surge in bankruptcies ahead of the new bankruptcy legislation. He said the company expects to incur a $500 million loss in the fourth-quarter as a result of the higher-than-expected bankruptcies and the company added $100 million to its loss provision to counter the elevated charge-offs. The company doesn't expect to achieve its previously forecast 3 percent return on operations in the fourth quarter as a result of the impact of the bankruptcies.

But Dimon said JPMorgan may experience a higher loss in the fourth quarter but expects to see a benefit in 2006 as "a lot of those people would have gone bankrupt anyway" and the company will be able to put those losses in the past and move forward.

On Monday, competitor Citigroup (Research) said it expects to incur $310 million in fourth-quarter losses due to the spike in bankruptcies ahead of the legislation. (For that story, click here.)

Speaking on a conference call with the press earlier Wednesday, JPMorgan's financial chief Mike Cavanagh said that the rise in short-term interest rates put pressure on the company's net interest margins, and the increasingly competitive market also weighed on deposit growth. He said JPMorgan will continue to open branches and grow its retail business but that there will be pressure on margins going forward.

Cavanagh said the impact of Hurricane Katrina and the higher-than-expected spike in bankruptcies ahead of the new bankruptcy legislation are an exception in an otherwise positive consumer credit environment.

But its equities and fixed-income trading offset weakness in the consumer business. Dimon said the company might have had a great quarter for trading but the company expects more normalized returns in the fourth quarter.

As for JPMorgan's integration of its July 2004 Bank One acquisition, company executives said the company is on track to produce its merger-related savings of $2.2 billion in 2004.

Dimon said the company will likely have the capability to do more acquisitions by mid-to-late 2006 but the decision would be based on the price, the strategic value of any potential merger and whether the company is confident that it will be able to execute the merger well.

In his press call earlier, Cavanagh declined to comment on whether the company would consider buying any of Refco's business but said that JPMorgan won't be materially impacted by Refco's woes.

Refco filed for bankruptcy Tuesday and agreed to sell its core futures brokerage unit to an investor group for $768 million, a key step to help rescue the embattled commodities and futures brokerage from collapse.

Shares of JPMorgan Chase recently climbed 23 cents, or 0.68%, to $34.