On Thursday morning, 17 May 2018, a team of ten animal caretakers and biologists successfully captured a 21-kilogram adult eagle ray from Burgers’ Ocean. Divers placed a sort of fish trap in a basin with 1.6 million litres of water, after which the adult male could be quickly scooped up and hoisted out. The animal was placed in a quarantine tank for 45 minutes. A parasite-destroying medicine had been added in advance, allowing the adult eagle ray to return to its basin completely clean. While he was out, the opportunity was taken to weigh and measure the animal: 21 kg with a wingspan of 1.30 metres. Royal Burgers’ Zoo is the largest spotted eagle ray breeder in the world.
Spotted eagle rays have been in Burgers’ Ocean—an eight million litres tropical coral reef aquarium—since 2000. The animal that was caught on Thursday has been living in Arnhem for 18 years and is the most important breeder of the group of eagle rays in Burgers’ Ocean. Since the arrival of these extraordinary cartilaginous fish, Burgers’ Zoo has been collecting data daily for scientific research.
The exact amount of food and what kind of food each individual eagle ray eats daily is recorded. By analysing this data, cycles can be recognised, and possible predictions can be made.
The Ocean’s biologist and his team of animal caretakers have also developed a technique for the easy collection of DNA material from individual eagle rays. They cut a small piece of the venomous stinger, to which a very thin layer of skin with DNA material is attached. This is completely painless for the animals and can be compared to cutting a fingernail. After a while, the venomous stinger grows back. The DNA material is important for determining paternity and species.