Boris, a Beluga sturgeon, swims in a tank at the Tennessee Aquarium after being transferred on Thursday. Boris weighs 212 pounds and measures approximately seven feet long.
Eleven days before opening night, two of the stars are dead.
Boris and Horace, a pair of beluga sturgeons from Russia, died over the weekend, only a day or two after being placed in their new tank for the upcoming River Giants exhibit, which opens April 28 at the Tennessee Aquarium.
Unknown to staff, the fish, each about 40 years old, were suffering different illnesses, and aquarium staff think the stress of moving them was more than they could handle.
Horace, who died Sunday, had kidney problems, and Boris -- who turned out to be a girl and died Saturday -- was suffering from egg issues.
In Horace, "one kidney was nothing but a blood clot the size of a dinner plate ... the other was putrid," said Jackson Andrews, director of operations and husbandry at the aquarium.
Boris's case was even more surprising. During the autopsy, staff discovered the sturgeon was a female, and her eggs, "unfortunately, had become septic," Andrews said.
"If there was any way that we would have known that these guys had problems internally, we never would have moved them," aquarium spokesman Thom Benson said.
Changing tanks is difficult for fish because they are placed in an unfamiliar environment, officials said. However, the shock of being chased, captured and confined for transport, all in a noisy environment inside the aquarium, can be even more stressful, Andrews said.
Because veterinarians also must catch the fish to examine them, staff don't give them regular check-ups to spare them the struggle. Andrews said that, in the long run, that technique is healthier for their fish.
Jackson Andrews, director of operations of husbandry for the Tennessee Aquarium"When a fish is behaving normally, you don't handle it," Benson echoed.
The sturgeons, each more than 7 feet long and about 200 pounds, seemed to be healthy before and immediately after the move, so staff had no reason to question their health. The deaths left the aquarium staff "quite depressed," Andrews said.
"With an animal like this, it's like part of the family," he said.
Both fish were sent from Russia to an aquarium in San Francisco in 1976, and Horace has been with the Tennessee Aquarium since opening day in 1992. In 2006, he was reunited with Boris, and the two were staples of the Volga River exhibit.
When the fish were placed in the River Giants exhibit last week, the aquarium's fish curator, Thom Demas, said beluga sturgeons could live to be 100 years old.
Veterinarians have sent the sturgeons' tissue samples to a University of Connecticut lab to determine the official cause of death.
While aquarium officials have begun talks with other aquariums about getting new sturgeons, it will be long after the River Giants exhibit opens, Andrews said.