Shares of Nymex Holdings Inc. rose more than 4 percent on Thursday as two analysts increased their earnings estimates the day after the parent of the New York Mercantile Exchange said it was raising trading fees for members.

JP Morgan analyst Kenneth Worthington raised his 2008 earnings estimate to $3.97 per share from $2.81 but retained his neutral rating on the stock.

Sandler O'Neill analyst Richard Repetto increased his per-share earnings estimate by 5 cents to $2.71 for 2007, and by 9 cents to $3.36 for 2008, saying Wednesday's price increase highlights Nymex's pricing power.

Repetto maintained his hold rating on the stock, but raised his price target to $136.

On Wednesday, Nymex, the world's largest energy futures market, raised fees for both its open outcry and electronic trading platforms. This is the second price increase in a year.

Worthington said in a note to clients that he did not expect the higher prices to depress trading volume.

Most existing traders are not price sensitive and will not trade away from Nymex due to the rate change, Worthington said.

Separately, Sanford Bernstein analyst Brad Hintz initiated coverage of Nymex with a market-perform rating and price target of $145.

The company's shares were up $5.68, or 4.3 percent, at $136.79 in morning New York Stock Exchange trading.

Some analysts have said the stock had been expensive in recent weeks because investors are expecting Nymex to be a buyout target.

Morningstar Inc. analyst Patrick O'Shaughnessy recently said NYSE Euronext, which owns the New York Stock Exchange, might be interested in acquiring Nymex.

An NYSE spokesman said on Wednesday that the company did not comment on rumors or speculation, while a Nymex spokeswoman declined to comment.