[Coral-List] Strobes blind seahorses?

Sarah Frias-Torres sfrias_torres at hotmail.com
Thu Apr 1 13:37:34 EDT 2010

Dear Coral-list,
>From my earlier work with seahorses and pipefishes, I have seen these feisty fish hunt their little prey with incredible accuracy, both in natural and aquarium conditions. I doubt permanent blindness occurs when exposed to flash photography, and the technical explanation for this has been well covered by a previous post.
The main concern is the stress, temporary and chronic, based on how much an individual seahorse is photographed at a given dive site. As far as I know, seahorses are diurnal predators, some species extending their hunt a bit over dawn or dusk. But they are not nocturnal. During the day, if we take away the time seahorses spend to hide both from predators (avoid being eaten), from prey (ensure eating), re-position themselves, and in case of breeding season, comply with the rigors of courtship (males and females) and "pregnancy" (males) we see the actual time left for an active and successful hunt is quite limited. If we add photographers strobe flashing their way to the unsuspecting seahorse, with the subsequent disorientation and re-adjustment required (for the seahorse), we can speculate the poor fellow needs a break. Night dives are another (even worse) story. 
Overall, rather than causing permanent blindness, I would be more concerned on how strobe-flash photography can increase vulnerability to predators and decrease (even temporary) hunting capabilities of seahorses, as cryptic and timid fish they are. 

Sarah Frias-Torres, Ph.D. Senior Postdoctoral Scholarhttp://independent.academia.edu/SarahFriasTorresOcean Research & Conservation Association 1420 Seaway Drive, 2nd Floor Fort Pierce, Florida 34949 USA http://www.teamorca.org

> Date: Thu, 1 Apr 2010 10:02:28 -0400
> From: allison.billiam at gmail.com
> To: dfenner at blueskynet.as
> CC: mel at briscoe.com; coral-list at coral.aoml.noaa.gov
> Subject: Re: [Coral-List] Strobes blind seahorses?
> 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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> -- 
> Reality, as usual, beats fiction out of sight.
> Conrad, 1915
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