A Gentle Giant’s Passing in the Secret Reef

On Wednesday, June 20, divers working in the Secret Reef exhibit before the Aquarium opened spotted a Sand Tiger Shark lying unresponsive at the bottom of the tank.

Upon receiving this news, Director of Aquatic Collections and Life Support Systems Thom Demas, Senior Aquarist Kyle McPheeters and Dive Safety Officer Mark Craven donned SCUBA gear, dove into the tank and swam the shark safely into a nearby acclimation pool to assess its condition.  

The Aquarium’s Sand Tiger Sharks have been at the Aquarium since 2004, about a year before the opening of the Ocean Journey building. Despite their large size and fearsomely toothy mouths, these sharks are gentle giants and veteran educational ambassadors. Through daily dive programs, the Aquarium’s Sand Tigers have dispelled myths about the aggressiveness of sharks and educated guests about the important role they play in marine ecosystems.

When they arrived, however, the Sand Tigers were already sexually mature adults and were estimated to be about 12 years old, already within the 11-15 years they can expect in the open ocean. In human care, this species’ median life expectancy is much longer —22-25 years — but at 26-27 years old, all of the Aquarium’s Sand Tigers have exceeded even this advanced age.

As with humans, the onset of advanced age is often accompanied by compromised health and age-related conditions, ranging from arthritis and heart disease to cancer and organ failure. And just like humans, animals age individually, some remaining hale and hearty into old age while others begin to show signs of health issues before reaching their life expectancy.

After its assisted relocation, the recovered Sand Tiger exhibited little to no response to efforts to rouse it. Feeding records show this shark had eaten well during its two most-recent feedings, but aquarium staff had been closely monitoring its health after noticing signs of slowed movement and diminished appetite in the past few months.

Based on the Aquarium veterinary team’s evaluation following the animal’s relocation, the shark was humanely euthanized.

Reaching this kind of decision is never easy and never made in a vacuum. Euthanasia is only chosen as the appropriate course of action after a consensus is reached that it’s in the animal’s best interest, says Aquarium Veterinarian Dr. Chris Keller.

“We’re guided by the principle that the quality of an animal’s life is so valuable that the length of their life is less important,” he says. “When an animal is in pain beyond our ability to help them, we have — as veterinarians and people who care for animals —one thing left in our arsenal with which we can relieve their suffering.”

A preliminary postmortem evaluation of the shark revealed age-related heart abnormalities and significant issues associated with its gastrointestinal tract. Tissue samples have been sent to an independent lab for final verification to ensure the shark’s health wasn’t reflective of an environmental issue that could affect other animals in the Secret Reef.

This shark’s passing follows two months after the loss of another Sand Tiger on April 12. As with this most recent recovery, that shark’s death was determined by a necropsy to be the result of a heart defect associated with its advanced age.

That so many animals at the Aquarium live long enough to experience conditions associated with being geriatric speaks to the quality of care and attention they receive, Dr. Keller says.

“In the wild, there is a selection process that takes place, and many of those animals don’t survive to the advanced ages you see here at the Tennessee Aquarium,” Dr. Keller says. “Providing animals with ideal circumstances — low stress, good nutrition and an environment that lends itself to them being ‘happy’ — is really, really important to us.

“The largest animals and the ones people most want to see, like these sharks, have been with us for a very long time, so we take great care to ensure their needs are met as they age. In essence, the Aquarium is a good place to be if you’re an animal, but it’s a great place to be if you’re an older animal.”

The Aquarium is actively seeking a source to acquire younger sharks that will be able to serve as new animal ambassadors in the Secret Reef, where they will inspire new generations to appreciate the fearsome beauty and ecological importance of sharks in the wild.