How brightness and color of artificial night light affect melatonin cycles and reproductive gene activity in roach fish

Melatonin concentrations were significantly lowered under nocturnal white light at just 1 lx.

• Artificial light at night (ALAN) at low intensities can disrupt melatonin rhythms in roach.
• Low intensity blue, green, and red light also significantly reduced melatonin levels compared to darkness.
• Light pollution in urban waters may impact biological rhythms in fish.
• The mRNA expression of gonadotropins was not affected by ALAN during the experiments.
• Implications of ALAN on the reproduction of roach could not be substantiated.

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