Changes in Blood Analytes of Newly Captured Killer Whales (Orcinus orca): Influencing Factors

Killer whales (Orcinus orca Linnaeus, 1758) are of major interest to scientists and society in general as apex predators and intelligent marine mammals. Despite the world’s practice of keeping some of them in sea pens (not indoor pools), nothing has been published about their blood analytes in such conditions. We aimed to fill this gap and provide data for 10 young killer whales. They were legally captured for sale, kept in sea pens in the Sea of Japan from July 2018 to August 2019, and then released back to the wild under the public pressure. These killer whales were under the care of veterinarians throughout this time, and blood samples were taken regularly. The animals were clinically healthy. We have retrospectively analyzed variations in the blood analytes due to different influencing factors. We have found effects of water temperature, period of adaptation to captivity (related to stress), and individuality on their blood analytes. No statistically significant correlation between killer whales’ sex and their blood analytes has been found. The results of our study contribute to a broader understanding of the killer whales’ physiology. Veterinarians can apply them to diagnose and manage health problems in these unique animals more accurately in order to increase chances of recovery.