Can fish blink? The answer, it turns out, is a resounding yes – though you might not be able to tell by looking at them.
For starters, fish don’t have eyelids in the traditional sense. Instead, they have a nictitating membrane, which is a clear or translucent third eyelid that sweeps across the eye from time to time. This membrane protects the eye from debris and keeps it moist, but it also allows the fish to blink.
So why don’t we see fish blinking all the time? Well, it turns out that fish blink at a much slower rate than we do – on the order of once every few seconds. And since they don’t have eyelids that close all the way, it’s not a very noticeable blink.
So the next time you’re at the aquarium, take a closer look at the fish and see if you can spot them blinking. They might not be as expressive as we are, but they’re definitely capable of it.