[Coral-List] Strobes blind seahorses?

[Bill Allison]

I suspect the question was as much about general harm to the fish as about
blinding it. Spotlighting a fish to take its picture, dazzling it with
flash, and distracting it with the whole procedure is likely to decrease its
chances of survival. I have seen predators take prey under these
circumstance.

On Thu, Apr 1, 2010 at 4:27 AM, Douglas Fenner <dfenner at blueskynet.as>wrote:

> Coral-listers,
>     When I take a picture with a flash on my digital camera and I take it
> on the reef in full sunlight in shallow water, it makes little difference
> to
> the photo.  I suspect that full sunlight in shallow water is about as
> bright
> as a flash.  Further, I've never seen a warning in the instruction book for
> a camera to not take a photo with flash closer than a certain distance from
> a person.  If it blinded a person or caused any permanent damage, the
> threat
> of lawsuits would mandate a lot of warnings.  If there is a solar eclipse,
> there are always many warnings not to look directly at the sun because it
> can damage your eyes.  Looking directly at the sun surely focuses too much
> light on a small spot on the retina.
>      I know some aspects of goldfish vision that have been tested are quite
> similar to us (the 3 color vision pigments), so my guess is that most fish
> would react similar to humans, though as Keven points out, fish specialized
> for night vision might have greater effects.  Seahorses and relatives are
> diurnal I believe.
>      I suspect this is an urban legend.  But I agree with the others that
> hard data is what would be needed to settle the question, and the things I
> am saying are really just speculation.  Charles seems to be on to
> something,
> if fish in public aquaria don't go blind, then it is unlikely to cause
> that,
> since they get plenty of flash photos taken of them.
>      Doug
>
> ----- Original Message -----
> From: "Keven Reed" <reedkc at comcast.net>
> To: "Julian @ Reefcheck Malaysia" <julian at reefcheck.org.my>; "'Melbourne
> Briscoe'" <mel at briscoe.com>; "'Coral-List'" <
> coral-list at coral.aoml.noaa.gov>
> Sent: Tuesday, March 30, 2010 6:22 AM
> Subject: Re: [Coral-List] Strobes blind seahorses?
>
>
> > Dear coral-listers,
> >
> >    Please note that we have gotten off the subject (Anthozoan
> > biology/research and coral ecology).  However, as an optometric
> physician,
> > I'll offer a couple general comments about a vertebrate; eg, seahorse
> > fish, having its retinal photoreceptor cells (rods & cones) temporally
> > 'bleached'--nothing to do with coral bleaching/loss of zooxanthellae--
> >
> >    The temporary blind spots of various colors we humans and other
> > vertebrate animals see after the strobe goes off while aimed into our
> > faces, represent the recycling time for the photopigment molecules in the
> > outer segments of our retinal rod and cone cells to flip back and forth
> > between different cis and trans forms of isomers of our visual pigments
> > before future photons can trigger another chemical event to fire a neuron
> > to the visual cortex of our brain, or the fish's brain.  The ratio of
> rods
> > and cones converging on a ganglion cell varies dramatically between
> > daytime hunting fishes and deep sea fishes.
> >
> >    Some terrestrial animals and some fishes have a reflective layer under
> > their retina that humans do not, the tapetum lucidum.  The tapetum
> > improves night vision in low light levels via increased internal
> > reflections in the posterior chamber of the eye much the way a starlight
> > scope amplifies a low light signal.  The tapetum is what gives that
> > metallic sheen to fish eyes and is what you see reflecting back to you
> > when your car beams or torch/flashlight catch a raccoon, deer or other
> > nocturnal beast in their eyes at night.
> >
> >    Having said all this, we should not equate a temporary bleaching, or
> > afterimage spot, to blindness, or permanent retinal damage.  Granted, a
> > dark adapted fish or terrestrial animal will have a more prolonged after
> > image, or temporary visual impairment before recovery than if the strobe
> > goes off in shallow, sunlight water.  I do not believe underwater strobes
> > blind seahorses or any other creature's retina, and I look forward to any
> > data that negates my hypothesis.
> >
> > Warmest regards,
> >
> > Keven
> >
> > Keven Reed, O.D.
> > Orange Park, Florida, USA
> > mobile:  904-505-7277
> > office:  904-264-1206
> >
> >
> >  ----- Original Message -----
> >  From: Julian @ Reefcheck Malaysia
> >  To: 'Melbourne Briscoe' ; 'Coral-List'
> >  Sent: Tuesday, March 30, 2010 12:24 AM
> >  Subject: Re: [Coral-List] Strobes blind seahorses?
> >
> >
> >  Hi Mel
> >  I only have anecdotal evidence, but some photographers have made the
> same
> >  comments to me. Would be interested to hear more evidence for or
> against.
> > I
> >  am also a diving instructor!
> >
> >  Julian Hyde
> >  General Manager
> >  Reef Check Malaysia Bhd
> >  03 2161 5948
> >  www.reefcheck.org.my
> >  Follow us on Facebook at www.facebook.com/rcmalaysia
> >
> >  "The bottom line of the Millenium Asessment findings is that human
> > actions
> >  are depleting Earth's natural capital, putting such strain on the
> >  environment that the ability of the planet's ecosystems to sustain
> future
> >  generations can no longer be taken for granted."
> >
> >
> >  -----Original Message-----
> >  From: coral-list-bounces at coral.aoml.noaa.gov
> >  [mailto:coral-list-bounces at coral.aoml.noaa.gov] On Behalf Of Melbourne
> >  Briscoe
> >  Sent: Monday, 29 March, 2010 2:55 AM
> >  To: Coral-List
> >  Subject: [Coral-List] Strobes blind seahorses?
> >
> >  I'm hearing in several diving forums that repeated use of strobes in
> >  underwater photography can blind seahorses. Is this based on evidence
> (if
> >  so, what?), or is it speculation and the precautionary principle at
> work?
> >
> >  Thanks -
> >  Mel Briscoe
> >  Consortium for Ocean Leadership
> >  and diving instructor
> >  ____________________________
> >  Sent from my HTC TouchPro 2
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> >
> >
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-- 
Reality, as usual, beats fiction out of sight.
Conrad, 1915