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Night lighting made the fish bolder by day

David Bierbach, IGB

Artificial night lighting made the guppies bolder in the daytime: they quickly got out of their hiding places and spent more time in the open space of the aquarium, scientists from Germany showed. At the same time, the speed of movement or the social behavior of fish was not affected by the lighting. A study of this is published in the journal Scientific Reports .

Light pollution, in particular, discourages  migratory birds that prefer to rest in cities, and trees in areas with bright night lighting awaken  after the winter a week earlier than in normal conditions. Ralf Kurvers of the Max Planck Institute for Human Development and his colleagues note that the influence of nocturnal light pollution on the daily behavior of animals has not been studied well enough.

Scientists for 10 weeks held three groups of 30 guppies ( Poecilia reticulata ) under different modes of night illumination: in the dark, with low light (0.5 lux – night light) and in bright light (about 5 thousand lux, about as winter noon). After that, they checked for three weeks how different illumination affects fish behavior during the day, using a special T-shaped labyrinth.

“Individuals who lived under weak and bright light, quickly left the starting shelter, and the fish from the group of bright light spent more time in the open part of the aquarium. Night artificial lighting did not affect other fish behavior, “the article says.Scientists believe that night lighting has increased the readiness of fish to risk – the consequences of this are difficult to predict, but it is likely that this can make them more vulnerable to predators. “We suspect that night lighting causes stress in fish, and under stress they usually show more risky behavior,” said Courvers, who is quoted by the press service of the institute.

Night light pollution affects the behavior of other living things: as British scientists have found , with a low level of illumination, wasps-horsemen prey on the aphids more actively, but in a brighter light they lose interest in mining.

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