Miller, S. L., Leri, F., Pushinsky, A. et al. 2023. Zebrafish (Danio rerio) distinguish between two human caretakers and their associated roles within a captive environment. Applied Animal Behaviour Science 267, 106053.

Zebrafish have become a popular biomedical model in recent decades, and are now maintained in laboratories worldwide. However, living within a captive environment can introduce novel environmental stressors and experiencing stress chronically can negatively affect animal welfare and, if applicable, how study results are interpreted. One method to potentially alleviate stress within captive environments is to introduce signaled predictability, i.e., conditioning captive populations to anticipate a future event by associating a visual or audio cue with the impending stimulus. A low-cost and easily accessible cue could be the caretakers themselves. Previous research has shown that archerfish can associate and distinguish between pictures of human faces, not human beings themselves. Therefore, it remains to be seen if fish, such as zebrafish can distinguish between two human caretakers, associated with different husbandry tasks. For this study, zebrafish were exposed to a caretaker who fed the fish only and a caretaker who chased the fish with a net, i.e., associated with an acute stressor. Caretaker duties were counterbalanced across two isolated laboratory shelving racks. Before performing tasks, the caretaker presented their face to all 10 fish tanks and then recorded the number of fish in the feeding area immediately. It was found that presentation of the stressor-caretaker did not significantly affect the number of fish within the feeding area, however, presentation of the caretaker associated with feeding led to a significant increase in the number of fish in the feeding area. By the end of the experiment, fish were more likely to be found in this area following the feeding-associated caretaker presentation, compared to the stressor-associated caretaker. These results suggest that zebrafish are capable of distinguishing between two human caretakers by learning to associate specific humans with husbandry procedures, particularly feeding. However, it is unclear exactly what visual cues, e.g., caretaker mannerisms, were utilized as caretaker faces were not isolated for presentation. Further research is needed to assess the repeatability of these results, as this research is novel, especially with respect to captive fish welfare.