Ocular Disease Prevalence in California Sea Lions In Human Care: Freshwater Versus Saltwater Housing

California sea lions (Zalophus californianus), are susceptible to various ocular diseases, with some literature suggesting a heightened risk for those kept in freshwater pools as opposed to saltwater. Given the potential implications of housing conditions on animal health, we wanted to analyze the ocular health of two distinct groups of sea lions kept at Nuremberg Zoo, one housed in freshwater and the other in saltwater. Data extracted from the animals medical records over a ten-year period were used to compare the incidence of eye conditions and other medical conditions observed. The results revealed no significant difference in the overall prevalence of eye diseases between the two environments. However, a distinct seasonal pattern was noted: sea lions kept in freshwater exhibited a peak in eye disorders during the summer months, while those in saltwater displayed a more uniform distribution of the occurrence of ocular diseases throughout the year. These findings suggest that sun exposure and water quality are potentially more influential factors in the development of ocular diseases in pinnipeds than salinity or UV radiation. Further studies are necessary to elucidate the underlying mechanisms and optimize care practices for these marine mammals. Simple SummaryThis study investigated the ocular health of California sea lions (Zalophus californianus) at Nuremberg Zoo, comparing those housed in freshwater pools to those in saltwater. An analysis of medical records over ten years showed no significant difference in the overall prevalence of eye diseases between the two groups. However, sea lions in freshwater experienced a peak of eye disorders in the summer, while those in saltwater had a more consistent occurrence throughout the year. These results imply that factors such as sun exposure and water quality may play a more crucial in ocular disease development than salinity or UV radiation. The study highlights the need for further research to understand these dynamics and improve care for marine mammals.