(Adds details on plan, reaction, background)
By Barbara Liston
ORLANDO, Fla., Aug 15 (Reuters) - Theme park operator SeaWorld Entertainment Inc. said on Friday it would nearly double the size of its San Diego killer whale tank and expand similar enclosures in Florida and Texas amid criticism over its treatment of the animals.
The company's amusement parks have come under attack after its handling of orcas was scrutinized in the 2013 film "Blackfish," which documented the killing of a trainer at the company's Orlando, Florida, park by a whale.
The company's shares rose 3 percent in early Friday trading before tapering off in the afternoon to trade up nearly 1 percent. Its shares lost more than a third of their value earlier this week when the company slashed revenue forecasts in part over flagging attendance it said was tied to the controversy.
"The new projects will build on SeaWorld's legacy of providing state-of-the-art, innovative homes for its animals," the company said in a statement.
Construction of a new, 1.5-acre whale tank at the company's park in California will begin next year and be completed in 2018, it said. The project will include a "fast water current," which is intended to stimulate the whales by allowing them to swim against moving water.
Orcas can grow to over 20 feet long and weigh up to 10 tons.
Expansions will follow for the company's tanks in Orlando and San Antonio, Texas, SeaWorld said.
The company also pledged $10 million for killer whale research.
The plan failed to win over People for Ethical Treatment of Animals, a harsh critic of the company's practices. The group said SeaWorld should instead put the captive orcas in seaside sanctuaries with the goal of releasing them into the ocean.
"This is a desperate drop-in-the-bucket move to try to turn back the hands of time at a time when people understand the suffering of captive orcas, and it will not save the company," PETA attorney Jared Goodman said in a statement. "A bigger prison is still a prison." (Additional reporting by Sruthi Ramakrishnan in Bangalore; Editing by Jonathan Kaminsky and Susan Heavey)