NEW YORK (AP) Investment manager Apollo Global Management said Tuesday that it agreed to acquire indoor water park operator Great Wolf Resorts for about $167.1 million.

New York-based Apollo Global Management LLC will buy Great Wolf Resorts Inc. for $5 per share, which represents a 19 percent premium over the Madison, Wis.-based company's closing stock price on Monday.

Based on Great Wolf's about 33.4 million diluted outstanding shares, the deal is worth about $167.1 million. Apollo valued the deal at $703 million including the assumption of debt.

The news sent Great Wolf shares up 90 cents, or 21 percent, to $5.09 in morning trading.

The offer was unanimously approved by Great Wolf's board, which is advising the company's shareholders to tender their shares.

"After a thorough assessment, we concluded that the proposal put forth by Apollo is the best way to maximize value for shareholders, who will receive a substantial and immediate cash premium for their shares," Kim Schaefer, Great Wolf's chief executive, said in a statement.

Also on Tuesday, Great Wolf said its board approved a shareholder rights plan, known as a "poison pill," which is a maneuver designed to deter any unsanctioned attempts to take over the company.

Great Wolf said the plan, which kicks in if someone other than Apollo acquires 12.5 percent or more of the company's stock, is designed to protect the company's shareholders in the event that someone other than Apollo attempts to buy the company.

The first Great Wolf Lodge resort opened in 1997 in Wisconsin Dells, Wis., and the company now operates 11 properties across the country.

The resorts generally include 300 to 600 rooms and a large indoor entertainment area of up to 100,000 square feet. They also feature arcade and game rooms, themed restaurants, spas, children's activities and other amenities, the company said.