Fish don’t sleep???

Old thread, sorry… but sitting here before the lights come on in the tanks…. And can see the Tin Foils swimming around again, in the dark… my camera grabs more light than the eye, so I tried a picture but it’s too dark, and it automatically flashed… they don’t hypnotically circle at the same depth, they seem to swim around, just like they would if the lights were on….
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I was watching them, when the 1st background light came on ( it’s still dark, the camera grabs more light ) and there is a minute or two of “confusion” as they must be actually waking up, switching from subconscious to conscious??? It’s just interesting that they can interact with each other, and the hard scape subconsciously… they are big, there are 5 of them, and all are moving, and yet they seem to swim normally, in the dark… there are 5-6 different light levels of the background lighting, this is still at the darkest setting
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There was a study, I can't find the paper now. Fish sleep better in soft water. The softer, the better apparently. Fish in harder water can be reluctant to sleep as the study showed they wake up a bit stiff.
 
Studying sleep in fish is a relatively new area of research. The paper below is pretty interesting of you want to see what the science knows to date.

Norman, H., Munson, A., Cortese, D., Koeck, B. and Killen, S.S., 2024. The interplay between sleep and ecophysiology, behaviour and responses to environmental change in fish. Journal of Experimental Biology, 227(11).
Sleep and Fish

ABSTRACT​


Evidence of behavioural sleep has been observed in every animal species studied to date, but current knowledge of the behaviour, neurophysiology and ecophysiology associated with sleep is concentrated on mammals and birds. Fish are a hugely diverse group that can offer novel insights into a variety of sleep-related behaviours across environments, but the ecophysiological relevance of sleep in fish has been largely overlooked. Here, we systematically reviewed the literature to assess the current breadth of knowledge on fish sleep, and surveyed the diverse physiological effects and behaviours associated with sleep. We also discuss possible ways in which unstudied external factors may alter sleep behaviours. For example, predation risk may alter sleep patterns, as has been shown in mammalian, avian and reptilian species. Other environmental factors – such as water temperature and oxygen availability – have the potential to alter sleep patterns in fish differently than for terrestrial endotherms. Understanding the ecological influences on sleep in fish is vital, as sleep deprivation has the potential to affect waking behaviour and fitness owing to cognitive and physiological impairments, possibly affecting ecological phenomena and sensitivity to environmental stressors in ways that have not been considered.

You can read the entire paper at the link above.
 

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