"I've had Lil B for two to three months and grown quite attached to him. He's got a lot of character to him. He's a little fighter. I thought he would make a nice gift for my girlfriend."
Mr Ayr was told live animals were not allowed on flights and Lil B would have to remain behind.
Passengers reported the flight being delayed by about 40 to 50 minutes but a Jetstar spokesman said the said the delay was only 10 minutes.
Luckily for Lil B, Wellington Airport's duty manager was on board and offered to have him taken to his home fish tank.
Mr Ayr gladly took up the offer because the tanks at his Roseneath flat were becoming overcrowded.
"My seven other flatmates and I are all passionate about fish. We've got a tropical fish tank and a goldfish tank. There's about 20 fish.
"Lil B's buddy El Nino [also named after a rapper] will miss him dearly. Taking him to Auckland was not only so my girlfriend - who also loves fish - could have a nice present, but also for his sake.
"I was just trying to do the best by my goldfish."
Mr Ayr was unimpressed by how Jetstar handled the situation and said he would not fly with the airline again.
Jess McDowall, a passenger on the flight, said the other passengers seemed amused and sympathetic to Mr Ayr.
"It was described as a 'discrepancy with baggage', which I thought was a little funny."
Jetstar's online policy says it reserves the right to refuse carriage of live animals.
The Jetstar spokesman said its staff were aware live animals were not allowed on domestic or international flights.
But they would follow up "to ensure the correct advice was being given".