Dive lights blinding aquatic life or permanently damaging their vision

[scagrotto]

aren't "most" of the creatures down there blind anyways?

My initial thought was to call BS on the idea because there's so little light when you get really deep that being blind can't be that big a problem. On further thought I'm figuring that a lot of the critters down there have really big eyes designed to gather as much light as possible. Big eyes that are really good at gathering light would certainly be more likely to be damaged by the (presumably very bright) lights of a deep sea submersible, kind of like our smaller eyes can be damaged by extremely bright lights such as the sun or an arc welder. Based on that I'm thinking it's entirely plausible that the light could do damage and maybe even result in some fish being unable to capture prey or avoid predators.

Then again, I'll presume that those deep sea submersibles don't usually lurk in the dark and suddenly turn their lights on when they think there's some big-eyed fish right in front of them. That would mean the fish would see them approaching and be able to avoid getting too close to the bright lights. Of course the corollary to that is that if you're down there specifically looking for those big-eyed fish maybe you do need to hang out with just dim lights until you see something and then light it up so you can really see it.

Perhaps the deep creatures would have something else affected by sub lights--something that enables them to kinda see in the pitch black?

Of course I'm only speculating, but other than the ability to see wavelengths we can't I don't know what could possibly allow them to "see". Blind cave fish rely on the ability to detect movement. Bats use echolocation (but actually have perfectly good eyesight, and see better than we do in any given amount of ambient light). Owls see very well with little light. Some deep sea creatures might use echolocation, but I expect that a lot of them rely on the ability to detect motion. I don't see how either ability would be damaged by light. OTOH, if they rely on wavelengths we don't see I expect that could be damaged about as easily as an ability to see the same wavelengths that we do.

 

[Stoo]

The greater risk to reef fish is that lighting them up brings them into full focus for their predators. When we did night dives from the T&C Explorer, large schools of huge snappers were constantly around us. If your light settled in some unsuspecting little guy, he would likely be nailed immediately. We kept our lights moving and if we did want to stop to see something, we would shine our lights "near" our subject, but not directly "on" it...

 

[Coop42]

Hi,
It was recently brought to my attention that when deep research submersibles use high powered lights to inspect the animals of the deep, those animals are permanently blinded and will suffer a slow death.

To quote the crowd on Wikipedia, [citation needed].

 

[EFX]

OTOH, if they rely on wavelengths we don't see I expect that could be damaged about as easily as an ability to see the same wavelengths that we do.

During one particular night dive in Coz I "lit up" several octopus with my LED light. The light produced from that narrow beam was white and quite bright when looking at it with human eyes. I was amazed when the octopus turned a bright aqua color that actually contrasted with the somewhat dull non-aqua surroundings. I'm wondering what effect this had, however brief, on the octopus as it produced the bio-chemicals needed to produce that color -- a color not normally found anywhere in its surroundings.

 

[scagrotto]

I was amazed when the octopus turned a bright aqua color that actually contrasted with the somewhat dull non-aqua surroundings.

Interesting. You may have noticed that some LED lights look very blue compared to incandescent lighting, and that some LED lighting is available in cool white, natural white and warm white. I'll guess that the octopus perceived the light in that color and was trying to blend in. A bit of quick Googling reveals that octopi are color blind, but have light-sensitive pigments called opsins on their skin. It's possible that, in a sense, they "see" color with their skin. You might be interested in reading this (or just search for opsins to get to the relevant part):

Octopi: The New Kings of Disguise | Mental Floss

 

[guyharrisonphoto]

I think the OP is referring to shining a light at normal scuba depths, and he just got the concern by analogy to what he read about the deeps.

I carry my 2000 lumen light every dive, day or night, because I dive on coral reefs and encrusted wrecks and enjoy seeing all the brilliant true color that is filtered out. Even shallow, very handy for looking under ledges for stuff. I do notice that if I put the hot spot on fishes there is a startle/notice response. Some bolt away a couple of feet, and some do not, and some bolt but then get used to it if I approach again. However, I have never seen a fish completely flee the scene in terror or go bumping into the reef afterwards.

From experience, I have learned not to light up the fish if I can avoid it, as I would rather have them around. But I am pretty sure it does not cause any harm to flash it on them if I want to see their true colors.