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.