Sea Life Scarborough's oldest resident seal passed away at the age of 29 on Wednesday, 22 August.
Bruno, a Harbour seal, had been living at the Sea Life Centre since 1989.
An early post-mortem investigation highlighted kidney issues, quite common in his species as well as old seals, as the cause of his death.
Lyndsey Crawford-Darwell, head of animal care, said: “There are so few symptoms when seals have kidney issues it becomes very difficult for us to spot before things become very serious. Bruno has lived here in Scarborough since before I arrived 18 years ago and was a huge part of our little SEA LIFE family.
"Both the whole team and myself are very upset at his passing but are finding comfort knowing we gave him a wonderful home for 29 years.”
Bruno, who was born in the wild, was rescued for rehabilitation but an outbreak of Phocine Distemper Virus (PDV), a viral disease common in seals, meant that he had to spend the rest of his life at the centre.
Lyndsey said: “Bruno was a real character. He developed a strong bond with one of our other residents Mando after he arrived. Mando was originally supposed to move to SEA LIFE Hunstanton but when it came time to move him Bruno was so determined not to have his best mate taken away he lay between us and Mando.
“They wanted to stay together so much Mando stayed with us and they spent the following years chasing each other round the pool! He leaves behind his other pool mates Pendle, Herbie and Ed who I’m sure will miss him as much as we will.”