“Three captive sharks have died and another is in critical condition today after a vital piece of equipment in their tank failed.
The sandbar sharks, in a tank at the National Marine Aquarium in Plymouth, perished after a measuring instrument that controls the amount of ozone being supplied to the tank broke down.
The malfunction, thought to have been a valve system failure, meant the amount of ozone being supplied to the shark tank increased.
While ozone is essential in small amounts to act as a disinfectant in tanks, excess amounts react with the seawater to create harmful chemicals that affect the sharks ability to get oxygen.
The remaining eight sharks in the tank appear to have suffered no adverse effects, but are being kept under close observation. A total of 50 fish in the same tank appear to be unaffected. However it is feared the fourth shark is unlikely to survive.
National Marine Aquarium chief executive Mike Leece has ordered a full investigation into the deaths.