Light pollution leads to risky behavior in fish



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China, Hong Kong, Hong Kong Island and Central District view through Victoria Harbor during the night laser show

New research suggests that exposure to artificial light at night causes guppies to adopt riskier behaviors during the day, which could put them at risk.

The environment of an animal is not only influenced by its location and physical environment, time is also important. About 60% of all invertebrates and 30% of all vertebrates are nocturnal and, for these species, darkness, moonlight and even starlight can play a crucial role in their behavior and survival. Artificial night light is well known to have a negative impact on many animal species by disrupting the sleep patterns of some animals while disrupting the activity of many others. For example, it can rule out refined nocturnal behaviors such as navigation, hunting habits or the ability to feed while avoiding predators.

Today, German researchers have shown that light pollution at night can even disrupt important survival behaviors during the day.

Ralf Kurvers of the Max Planck Institute for Human Development (MPI) and his collaborators at the Leibniz Institute for Freshwater Ecology and Inland Fisheries (IGB) have looked closely at how night light pollution affects the Trinidadian guppies (Poecilia reticulata).

Three groups of guppies were exposed to the same light levels during the day, but at night each group was exposed to a different lighting level. One group experienced total darkness at night, while the second group was exposed to low light at a level comparable to that of a conventional street lamp. Meanwhile, the third group of guppies was exposed to bright light. This was happening every night for ten weeks, after which the scientists conducted a series of tests to see if any of the Guppies' behaviors had changed.

Guppies exposed to a weak or bright ALAN showed no difference in swimming speed or sociality compared to guppies that had experienced dark nights, but they left their hiding places faster during the day and tended to swim more often in the night. the open areas of the aquarium. which is considered a risky move for these small fish.

"We suspect that night light causes a stress response in fish, and that fish generally increase their risk-taking in case of stress," says Kurvers.

Light pollution makes the guppies of Poecilia reticulata more courageous in the light of dayDavid Bierbach, IGB

This might not work so well for the fish in question, says David Bierbach, researcher at the IGB.

"The consequences of this increased risk taking are hard to predict," he says, "but it is possible that birds or other fish are more susceptible to predation."

The results could also help shed light, so to speak, on how ALAN could contribute to a high stress response in humans during the day.

Original search:

Kurvers, RHJM et al (2018) Artificial night light affects the exit of a refuge and the use of space in guppies. Scientific reports 8

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China, Hong Kong, Hong Kong Island and Central District view through Victoria Harbor during the night laser show

New research suggests that exposure to artificial light at night causes guppies to adopt riskier behaviors during the day, which could put them at risk.

The environment of an animal is not only influenced by its location and physical environment, time is also important. About 60% of all invertebrates and 30% of all vertebrates are nocturnal and, for these species, darkness, moonlight and even starlight can play a crucial role in their behavior and survival. Artificial night light is well known to have a negative impact on many animal species by disrupting the sleep patterns of some animals while disrupting the activity of many others. For example, it can rule out refined nocturnal behaviors such as navigation, hunting habits or the ability to feed while avoiding predators.

Today, German researchers have shown that light pollution at night can even disrupt important survival behaviors during the day.

Ralf Kurvers of the Max Planck Institute for Human Development (MPI) and his collaborators at the Leibniz Institute for Freshwater Ecology and Inland Fisheries (IGB) have looked closely at how night light pollution affects the Trinidadian guppies (Poecilia reticulata).

Three groups of guppies were exposed to the same light levels during the day, but at night each group was exposed to a different lighting level. One group experienced total darkness at night, while the second group was exposed to low light at a level comparable to that of a conventional street lamp. Meanwhile, the third group of guppies was exposed to bright light. This was happening every night for ten weeks, after which the scientists conducted a series of tests to see if any of the Guppies' behaviors had changed.

Guppies exposed to a weak or bright ALAN showed no difference in swimming speed or sociality compared to guppies that had experienced dark nights, but they left their hiding places faster during the day and tended to swim more often in the night. the open areas of the aquarium. which is considered a risky move for these small fish.

"We suspect that night light causes a stress response in fish, and that fish generally increase their risk-taking in case of stress," says Kurvers.

Light pollution makes the guppies of Poecilia reticulata more courageous in the light of dayDavid Bierbach, IGB

This might not work so well for the fish in question, says David Bierbach, researcher at the IGB.

"The consequences of this increased risk taking are hard to predict," he says, "but it is possible that birds or other fish are more susceptible to predation."

The results could also help shed light, so to speak, on how ALAN could contribute to a high stress response in humans during the day.

Original search:

Kurvers, RHJM et al (2018) Artificial night light affects the exit of a refuge and the use of space in guppies. Scientific reports 8

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