To cue or not to cue, that is the question: Alarm cues in the eastern mosquitofish (Gambusia holbrooki)

Many fish species rely on indirect predator avoidance strategies, such as chemical alarm cues, which increase the fitness of conspecifics. Individuals are alerted to potential dangers on the basis of cues released by conspecifics in jeopardy. Disturbance cues have been documented in Iowa darters (Ethiostoma exile) and brook trout (Salvelinus fontinalis) and may occur in eastern mosquitofish (Gambusia holbrooki). We conducted experiments to determine whether visual or chemical cues triggered antipredatory responses in eastern mosquitofish. We examined behaviors such as darting, freezing, and hiding when visually isolated conspecifics were chased by a mimic predator. Aquaria were divided by an opaque water-permeable barrier allowing free diffusion of chemical cues while preventing visual contact. Fish on one side of the barrier were disturbed and the behaviors on both sides were recorded. A significant increase in darting (p=0.0293) in preliminary tests indicates a strong cue response. Our current procedure is designed to better assess hiding behavior, by including more natural structures in test tanks.