AbstractMany fish form schools and visually track the position of their neighbors in a 3D environment. In this study, we assessed whether zebrafish modified their spacing behavior and interaction time in an additive or multiplicative way relative to multiple sources of visual social information using video playbacks. We simultaneously manipulated: (a) the magnitude of the social cues (by varying the size of the virtual fish), (b) the level of social risk (low, high based on the position of the virtual fish in the water column), and (c) the perceived depth of the social cues (visual horizon absent or present). Each of these factors independently affected spacing behavior (zebrafish increased the separation distance with larger virtual fish, under lower visual social risk, and when depth perception was enhanced), but they did not affect interaction time. However, some of these factors interacted significantly, such that their effects on social behavior depended on each other. For instance, zebrafish decreased their separation distance under high vs. low risk conditions when the virtual fish was the same or smaller size, but this risk effect disappeared with larger virtual fish likely to avoid aggression. Also, zebrafish increased their separation distance when perceived depth was enhanced under low risk, but the perceived depth effect became less pronounced under high risk probably due to dilution effects. Overall, the effects of certain visual social parameters depend on the intensity of other visual social parameters, ultimately tuning up or down different social behavioral responses. We discuss the implications for the spatial organization of fish schools.Significance StatementMany fish form schools and visually track the position of their neighbors in a 3D environment. We found that zebrafish consider multiple visual social sources of information simultaneously to modify their neighbor distance. Thus, their spacing behavior appears to follow multiplicative rules, whereby the spacing response to a visual social parameter depend on the intensity of a different visual social parameter.
Estimating Birth Stopping and Spacing Behavior