The object permanence in detour behaviors of marine and freshwater fishes

The capacity for detour behavior to reach a visible social target has been documented in both marine (Chromis viridis, Chrysiptera parasema, Dascyllus aruanus) and freshwater fish species (Xenotoca eiseni, Danio rerio) using a "four-compartment box" paradigm involving an opaque obstacle. In the first experiment, marine fish were observed in a setup where access to conspecifics was blocked by a central barrier. Two symmetrical openings in the middle of the corridor allowed fish to momentarily lose sight of the goal in order to navigate around the barrier. The marine species investigated displayed active searching in the compartments closest to the social stimuli. In a second experiment, the detour performance of one marine species (Dascyllus aruanus) was compared to that of two freshwater species (Xenotoca eiseni and Danio rerio) using a modified apparatus. This version featured extended compartments, increasing the physical distance between the subject and the goal, allowing for assessment of spatial factors in successful detouring. All species demonstrated the ability to navigate around the barrier. Furthermore, Danio rerio exhibited distinct exploration patterns within the compartments, indicating a sustained interest in locating conspecifics and hinting at a possible retention of social object permanence. These findings underline the ecological relevance of detour behaviors in fish, beyond specific environmental or phylogenetic constraints.