Dynamic visual noise promotes social attraction in a shoaling fish

Gathering information from the environment allows animals to make informed behavioural decisions, with individuals sampling information either privately, or via social cues from group members. Because environmental noise can disrupt the ability of animals to gather information from their environment, social behaviour could be disrupted by environmental noise, or adapted to mitigate the costs and risks associated with compromised perception in noisy environments. Here we test how the presence of water caustics, a natural form of visual noise prevalent within shallow aquatic habitats, affects the social decisions of shoaling fish. In a classic experimental paradigm, individual three-spined sticklebacks (Gasterosteus aculeatus), were given a choice between associating with two conspecific shoals differing in size while immersed in different levels of visual noise. While the presence of visual noise did not affect the preference of individual fish to associate with the larger of the two shoals, fish showed greater social attraction to conspecifics as noise levels increased, measured by a reduction in the distance they kept from the shoals. Our findings suggest that when the ability of individuals to extract visual information from their environment becomes more challenging, fish increase their reliance on social interactions, potentially to mitigate the consequences of having reduced perceptual abilities in noisy environments