QuickCheck: Do fish sleep?

SWIMMING around all day and night, one can’t help but wonder if fish ever sleep. Do they?

Verdict:

PARTIALLY TRUE

FISH do sleep, but not in the same way that other animals on land do.

Most fish rest by reducing their activity and they "sleep" with their eyes open because most do not have eyelids to get some shut-eye.

"The nature of fish 'sleep' is an area of active research.

"Research shows that fish may reduce their activity and metabolism while remaining alert to danger," according to an explanation on the United States’ National Oceanic and Atmospheric Administration (NOAA) website.

When they rest, some fish float in place, while others wedge themselves into a secure spot in the mud or coral.

"Some even locate a suitable nest.

"These periods of ‘suspended animation’ may perform the same restorative functions as sleep does in people," said the NOAA.

According to the education site Wonderopolis,org, most fish still need to keep moving even when they're sleeping.

"This is so that they keep a constant flow of water moving past their gills to maintain a proper oxygen level in their bodies," it said.

For some larger fish, they may swim at a slower rate while smaller fish might simply move their fins occasionally.

References:

1. https://oceanservice.noaa.gov/facts/fish-sleep.html

2. https://wonderopolis.org/wonder/do-fish-sleep-with-their-eyes-open