The Aquarium in the Adriatic city of Pula on the Istrian peninsula recently got a new pet, an adorable baby thornback ray, first of its species born in an aquarium in Croatia.

The new bundle of joy, named Lucky (Srecko) by the Aquarium staff, spends his days in a tank with his six brothers and sisters, happily swimming and snacking on lab-grown krill.

At only one month old, he is already melting hearts with his wide, cheerful smile.

“This charismatic smile of his has won over all of us in the aquarium, and I think he is slowly winning over the whole of Croatia. He is indeed very special,” said Marina Benazic, a biologist in the Aquarium.

The pups cannot eat independently yet, so they are fed every hour.

“These little rays are not used to catching their own food yet, so we offer them krill. (Lucky) cannot catch them yet on his own because they are too fast for him,” said biologist Matea Stankic.

For now, smiley Lucky and his siblings measure only 10 centimetres in length. When they reach maturity though, in seven to nine years, they will be proper thornback rays, more than half a meter long.

Since these pups are the first ones born in any aquarium in Croatia, there is no law to clarify where they will go when they grow up. Lucky may end up in another aquarium with his brothers, in the southern coastal city of Dubrovnik, or he may be released into the Adriatic.

“We are working on that for Lucky, there are various EU programmes for reintroduction. We are in talks with the Ministry (of Maritime Affairs), and we’re expecting a positive response,” said Pula Aquarium manager, Marija Aleksandra Bel-Dajkovic.

It is not known how many thornback rays there are in the northern Adriatic, but marine biologists believe their population has halved in the last 20 years. Although endangered, the species is not protected by law.

“Cartilaginous fishes (which include rays and sharks) are in danger of uncontrolled fishing, overfishing, because it takes a lot of time for them to fully develop,” Bel-Dajkovic said.

Lucky would be just fine in the wild, that largest aquarium of them all. After all, it is in his nature.

For now, though, he and his little siblings are more than content under the watchful eye of their carers in the Pula Aquarium.