Many species cohesively navigate their environment as a group. This includes fish schools and shoals, where group structure emerges from social interactions, which can subsequently facilitate adaptive advantages such as collective foraging. While previous work has characterized how group structure emerges from social interactions, less is known about how collective behavior is influenced by external factors (e.g., resource availability) and internal physiological states (e.g., hunger), and their underlying behavioral and neural mechanisms. To address how collective behavior is influenced by both stimuli and state, here we examine how social structure shifts across hunger states and prey stimuli in two distinct fish species: the black-spot piranha (Pygocentrus cariba) and the micro glassfish (Danionella cerebrum). First, we recorded groups of freely-swimming fish in different hunger states with or without prey, and applied multi-animal pose estimation to the data to assess group dynamics. In piranhas, we identified a transient period of enhanced social coordination after the introduction of prey, characterized by a large and rapid increase in speed. Hunger did not alter baseline behavior, but potentiated this stimulus-evoked behavior. In contrast, hungry glassfish exhibited cohesive social structure regardless of prey availability, and coordinated schooling was suppressed in sated animals. This suggests that hunger states may alter the visual perception of social partners. We are currently investigating the mechanisms of hunger-modulated schooling by imaging biological motion-associated neural activity across the brain of the small transparent glassfish. By investigating how hunger state and prey stimuli influence collective behavior, our comparative behavioral analysis reveals how both internal physiological states and external stimuli can have distinct effects on social structure. Our work will ultimately offer insights into the neural basis of collective behavior.