There are a lot of fish facts, and fish myths.

So I'd like to ask if this is fact, or myth...

Does sunlight hurt the eyes of fish because they have no eyelids? I've heard that is why feeders should be set in morning & evening, rather than the middle of the day.

But is it true?

PS If anyone wishes, they are welcome to ask further fact or myth questions in this thread. But first, what about fish eyes?

I don't know about "hurt" but I think the preference of fish is to be in more shaded water for feeding. Looking up at the sky shouldn't be any different for them than for us.

Fish eyes do not work like ours (color , rods and cones etc.). Their senses are developed for water not air so all of them are different. I will try to find some more info.

Since fish do not have eye lids and most do not have an adjustable iris (most with a fixed pupil) they regulate the amount of light entering the eye by moving deeper or shallower. In humans and many other animals the pupil size (opening) is adjusted by the iris (colored part of the eye).

Thanks for all the replies! Like most freshwater fishermen, I long ago realized that calm sunny days were usually not good for the bite, except during early spring when the water is cold. Normally low light conditions, such as caused by waves, clouds, dawn or dusk, are best.

Guess I'm mostly curious about why. Is it easier to catch prey under low light conditions? Do bright conditions limit their eyesight, or maybe even hurt their eyes? Don't know if there's been a lot of research on the subject, but ...

In general fish are near sighted and their eyes are much more sensitive to light than ours. I have read that LMB have eyes that are five times more senstive than ours. In addition color vision in fish is much different than ours and can vary quite a bit between different types of fish. LMB have two cones (color recpetors) attached per nerve while we only have one. Fish that live in the deeper depths of the ocean can have five or more cones attached per nerve. Water does filter out certain wavelengths of color as depth changes.

This is a good read.

https://en.m.wikipedia.org/wiki/Vision_in_fishes

I have an LED company. I worked with a lettuces producer to grow lettuces with dark leaves. The key was UV light. We added some UV and infrared LEDs to the mix. Long story long I had an extra light so we added it over top of a 38 gallon bow front fish tank with live plants. My thoughts were that the plants would just love the light and grow like crazy. Well to my dismay the plants all melted in two days and the platys went completely blind. Their eye clouded over and never repaired. Most died because they could not see to eat. The light only ran for 8 hours a day 4 two off 4 again.

Bummer for sure.
I take it the lettuce grew well? So why would aquatic organisms respond so differently to UV? UV is used to treat drinking water in some cases.
I'm now really curious what happens here.

Yes there is some indication that some fish may see in the UV spectrum. LMB have better low light vision than BG so they have the advantage in hunting in low light. LMB also hunt at night while BG are mostly dormant.

The UV gave the right lettuce the deep red or purple colours. This fella was growing, washing, packaging into clam shells for Wendy's fast food salads. They wanted that dark colour for their salad mix. The LED over HPSodium gave a 90% increase in germination and 10X less power consumption. We ended up with UV lights in T5's. Basically a T5 with out much phosphorus in it to colour up the lettuce.

I am not sure if it was the UV or the infrared. Infrared is really bad for our eyes as well as UV.