People for the Ethical Treatment of Animals has written the Tampa Bay Rays, asking the team to remove its rays "touch tank" from Tropicana Field.
The letter to team counsel John Higgins from Delcianna Winders, director of PETA's captive animal law enforcement, claims the tank, behind the right-center field wall, places the fish in danger of being injured or killed by an errant ball.
"And as recent events have demonstrated, that threat is all too real," Winders wrote.
PETA's request comes a week after Detroit Tigers slugger Miguel Cabrera hit a home run that splashed into the tank. It has happened one other time, by Luis Gonzalez of the Los Angeles Dodgers, in 2007. No fish were struck in either incident.
The team had no comment on the letter.
The 10,000-gallon tank with more than 30 cownose rays was set up by the team in 2006 through a partnership with The Florida Aquarium to educate fans about aquatic life and conservation, and to help promote the nonprofit Tampa aquarium. According to the team's website, the rays were caught in Tampa Bay and are cared for by aquarium personnel.
Only 50 people at a time are allowed access to the tank on game days. Fans may purchase ray food, with proceeds going to the aquarium and the team's charity foundation, the team's website said.
A copy of the letter was emailed to The Tampa Tribune by a PETA media representative. In the letter, PETA asks the team and aquarium to work together to rehabilitate the rays and return them to their natural habitat.
"The rays held captive at Tropicana Field not only were traumatically taken from their vast home waters but also are subject to harassment, loud crowds, and even baseballs capable of seriously injuring them," Winders said in a statement to the media. "When it comes to compassion, the Rays are batting .000."
Her letter said PETA was also concerned about the Rays offering to donate $5,000 in charity when a ball lands in the tank. The letter said the Rays previously claimed to be "unaware of any such offer" although "references to it remain on your website."
Some mentions of the donation were removed from the website since the letter was sent, a PETA spokeswoman said.
"It would seem that the Rays have finally begun to remove their deadly contest from their site, five years after they first denied its existence," PETA media coordinator Sophia Charchuk wrote in an email to The Tampa Tribune. "We hope that this signals the beginning of the end for the tank, where these inspiring animals are living a life sentence with no parole."
PETA claims to represent more than 3 million members and supporters. The animal rights group has received criticism for what some have called radical protests and campaigns, such as those where models are scantily dressed or nude.
Tribune reporter Roger Mooney contributed to this report.