Nighttime lighting affects guppies' daytime behaviour

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Nighttime lighting affects guppies' daytime behaviour

September 23, 2018 - 06:08
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For marine animals, streetlights, harbour light, and lights from boats are some sources of light pollution at night. Studies have shown fish to become disoriented when swimming near lights at night, and the timing of their migration and schooling behaviour have also been shown to be affected. A new study takes a look at how nighttime lighting affects guppies.

Being exposed to light during the night can affect guppies' behaviour. (These are not the guppies involved in the study)

Being exposed to light during the night can cause changes in the behaviour of guppies, according to a new study published in the Scientific Reports journal.

Led by researchers at the Leibniz-Institute of Freshwater Ecology and Inland Fisheries (IGB) and the Max Planck Institute (MPI) for Human Development, the study comprises guppies that were divided into three groups.

One group were placed in total darkness during the night; the second group was exposed to dim lighting (similar in strength to that of a street light; the third group received bright lighting during the night. During the day, all the fish were exposed to the same bright-light conditions.

After ten weeks, the fish's behaviour was assessed. It was found that the groups of fish that were exposed to light during the night—be it dim or bright—were more likely to engage in risky behaviour; they were more active at night, "left their hiding places faster during the day and swam more often in the riskier, open areas of the aquarium," according to the Institute's press release. There was no change in swimming ability or social behaviour.

"We suspect that the nocturnal light causes a stress response in the fish, and fish generally increase their risk taking when experiencing stress", said lead author Ralf Kurvers, from the MPI for Human Development.

The consequences in this behavioural change may cause the fish to be more prone to being preyed upon by birds and other fish, said co-author IGB researcher David Bierbach.

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