New publication: Flash photography impacts on fish – To flash or not to flash?

The final paper of my PhD thesis has just been published online in the journal Scientific Reports. The paper, titled “Behavioural and pathomorphological impacts of flash photography on benthic fishes” explains the effects of typical diver behaviour while photographing small critters such as seahorses or frogfishes.

The paper itself can be a tad technical, so with the help of two co-authors (Dr. Ben Saunders and Tanika Shalders), I wrote this summary of the research, which was published first at The Conversation (original article here).


We all enjoy watching animals, whether they’re our own pets, birds in the garden, or elephants on a safari during our holidays. People take pictures during many of these wildlife encounters, but not all of these photographic episodes are harmless.

There is no shortage of stories where the quest for the perfect animal picture results in wildlife harassment. Just taking photos is believed to cause harm in some cases – flash photography is banned in many aquariums as a result.

But it’s not always clear how bright camera flashes affect eyes that are so different from our own. Our latest research, published in Nature Scientific Reports, shows that flash photography does not damage the eyes of seahorses, but touching seahorses and other fish can alter their behaviour.

Look but don’t touch

In the ocean it is often easier to get close to your subject than on land. Slow-moving species such as seahorses rely on camouflage rather than flight responses. This makes it very easy for divers to approach within touching distance of the animals.

Previous research has shown that many divers cannot resist touching animals to encourage them to move so as to get a better shot. Additionally, the high-powered strobes used by keen underwater photographers frequently raise questions about the welfare of the animal being photographed. Do they cause eye damage or even blindness?

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Does flash harm fishes? Photo: Luke Gordon

Aquariums all around the world have taken well-meaning precautionary action. Most of us will have seen the signs that prohibit the use of flash photography.

Similarly, a variety of guidelines and laws exist in the scuba-diving community. In the United Kingdom, flash photography is prohibited around seahorses. Dive centres around the world have guidelines that include prohibiting flash or limiting the number of flashes per fish.

While all these guidelines are well-intended, none are based on scientific research. Proof of any damage is lacking. Our research investigated the effects of flash photography on slow-moving fish using three different experiments.

What our research found

During the first experiment we tested how different fish react to the typical behaviour of scuba-diving photographers. The results showed very clearly that touching has a very strong effect on seahorses, frogfishes and ghost pipefishes. The fish moved much more, either by turning away from the diver, or by swimming away to escape the poorly behaving divers. Flash photography, on the other hand, had no more effect than the presence of a diver simply watching the fishes.

For slow-moving fishes, every extra movement they make means a huge expense of energy. In the wild, seahorses need to hunt almost non-stop due to their primitive digestive system, so frequent interruptions by divers could lead to chronic stress or malnutrition.

The goal of the second experiment was to test how seahorses react to flash without humans present. To do this we kept 36 West Australian seahorses (Hippocampus subelongatus) in the aquarium facility at Curtin University. During the experiment we fed the seahorses with artemia (“sea monkeys”) and tested for changes in their behaviour, including how successful seahorses were at catching their prey while being flashed with underwater camera strobes.

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The aquaria were the seahorses were housed during the experiment

An important caveat to this experiment: the underwater strobes we used were much stronger than the flashes of normal cameras or phones. The strobes were used at maximum strength, which is not usually done while photographing small animals at close range. So our results represent a worst-case scenario that is unlikely to happen in the real world.

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West Australian seahorses (Hippocampus subelongatus) in their aquarium at Curtin University

The conclusive, yet somewhat surprising, result of this experiment was that even the highest flash treatment did not affect the feeding success of the seahorses. “Unflashed” seahorses spent just as much time hunting and catching prey as the flashed seahorses. These results are important, as they show that flashing a seahorse is not likely to change the short-term hunting success (or food intake) of seahorses.

We only observed a difference in the highest flash treatment (four flashes per minute, for ten minutes). Seahorses in this group spent less time resting and sometimes showed “startled” reactions. These reactions looked like the start of an escape reaction, but since the seahorses were in an aquarium, escape was impossible. In the ocean or a large aquarium seahorses would simply move away, which would end the disturbance.

Our last experiment tested if seahorses indeed “go blind” by being exposed to strong flashes. In scientific lingo: we tested if flash photography caused any “pathomorphological” impacts. To do this we euthanised (following strict ethical protocols) some of the unflashed and highly flashed seahorses from the previous experiments. The eyes of the seahorses were then investigated to look for any potential damage.

The results? We found no effects in any of the variables we tested. After more than 4,600 flashes, we can confidently say that the seahorses in our experiments suffered no negative consequences to their visual system.

What this means for scuba divers

A potential explanation as to why flash has no negative impact is the ripple effect caused by sunlight focusing through waves or wavelets on a sunny day. These bands of light are of a very short duration, but very high intensity (up to 100 times stronger than without the ripple effect). Fish living in such conditions would have evolved to deal with such rapidly changing light conditions.

This of course raises the question: would our results be the same for deep-water species? That’s a question for another study, perhaps.

So what does this mean for aquariums and scuba diving? We really should focus on not touching animals, rather than worrying about the flash.

Flash photography does not make seahorses blind or stop them from catching their prey. The strobes we used had a higher intensity than those usually used by aquarium visitors or divers, so it is highly unlikely that normal flashes will cause any damage. Touching, on the other hand, has a big effect on the well-being of marine life, so scuba divers should always keep their hands to themselves.

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Look, take pictures, but don’t touch!


NOTE: I realise that this is a controversial topic in underwater photography. If you have relevant questions, comments, or thoughts you want to share, feel free to add them in the comment section below. If you are interested, I would highly advise you to read the original research paper via this link. The paper is open access, so anyone can read and download it. If you have specific questions about the paper, you can always contact me via email here.

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Guestblog: Frogblogging – insights in the world of frogfishes

IMG_0737This month’s guestblog is written by Daniel Geary, the resident marine biologist at Atmosphere Resort in Dauin, Philippines. It’s safe to say that Daniel is very passionate AND knowledgeable about frogfishes. He’s been studying them for years in Dauin and even wrote (and teaches) a PADI speciality course on these awesome critters! In this blog he gives a taste of some of the many ways frogfish are fantastic and deserve a closer look.


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Longlure frogfish (Antennarius multiocellatus) from Florida

Frogfish. You have probably heard of them, and if you’re a diver you might have seen one or two before. You have definitely swam right past a few of them without knowing they were there. Although most of them have a face only a mother could love, behind this outer layer exists a well-adapted, expert fisherman with amazing camouflage capabilities. They are more than just a lazy, camouflaged blob that sometimes doesn’t change location for a year.

Frogfish are anglerfish, although they are what I call a shallow, less ugly version of anglerfish. They have a rod and a lure that they actively fish with when necessary. Their fins look like limbs that somewhat resemble those of a frog. They must inhale water though their mouth to then push it out of their gills which aids in locomotion. Frogfish are experts at changing color and can change color multiple times, usually to blend in with their surroundings. Normally a full color change takes about 2 weeks, but frogfish have been witnessed to change color in under ten seconds when disturbed by divers’ bubbles and needing to switch to a different coral.

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The same giant frogfish (Antennarius commersoni) changing colour in two weeks

There are around 50 species of frogfish, with a new species or two being described every few years. Frogfish can be found worldwide in tropical and subtropical waters (but not in the Mediterranean). Some species are only found at a handful of dive sites, others are only found in one country or continent. A handful of species are found in the majority of the warm water areas, but only the Sargassumfish is found worldwide. There have been a few occasions where Sargassumfish were found all the way up in the cold waters of Norway and Rhode Island – way out of their preferred habitat, but they live their lives floating in seaweed and/or other debris and are at the mercy of the ocean currents.

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Sargassum frogfish (Histrio histrio) often wash up on the shore of the Atmosphere housereef, when they do, they get released back into deeper water

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Painted frogfish (Antennarius pictus) using its lure to attract prey

Frogfish are ambush predators which is why they seem to be so lazy. The less they move, the better predators they can become due to algae, coral polyps, and any other organisms that use the frogfish as habitat. I call this being lazily efficient, or efficiently lazy. Frogfish will make minimal adjustments to their body positioning before they begin to lure prey, although sometimes the frogfish are so camouflaged that they don’t need to actively attract prey. Frogfish swallow their prey whole by opening their mouth and creating an instant vacuum since the volume of the mouth increases up to twelve times the original amount. This means frogfish can swallow their prey whole in six milliseconds. They feed on a variety of organisms, depending on where the frogfish lives. Generally they like small fish like cardinalfish, shrimps and crabs, and sometimes other frogfish. They can comfortably swallow prey that is their own size, and with a bit of effort they can swallow prey up to twice their size, although this can result in the death of the frogfish if the prey item is too large and gets stuck in their throat. Frogfish do not have many predators, but they are sometimes preyed on by moray eels, triggerfish, and lizardfish. Flounder will sometimes suck up juveniles from the sand and fishermen in the Philippines have been known to capture and eat Giant Frogfish.

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This giant frogfish (Antennarius commersoni) bit of more than it could chew and did not live to tell the tale. Photo taken at Apo Island

 

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Frogfish egg raft

Frogfish have been known to eat each other if they get too close, especially after failed mating attempts. A male will approach a female when she is bloated with eggs. He will do his best to show off for her, which includes expanding his fins to their maximum sizes, rapidly opening and closing his mouth, as well as violently shaking his body. At this point, the female either accepts him or tries to eat him. If accepted, he gets to stand next to the female, which is the frogfish equivalent of holding hands. Once he is ready to mate, he will start again with his flashy moves, but this time bouncing around the female. Sometimes he has to physically swim her off the substrate to mate, other times she is able to swim on her own. Once they are a meter or two above the substrate, the female releases her egg raft, causing her to spin rapidly. The male then fertilizes this egg raft, also spinning rapidly. Both the frogfish then return to the bottom as the eggs float off into the distance. The eggs will hatch a few days later and become tiny planktonic frogfish babies, which will continue to float for a month or two until they are big enough to settle in the substrate, change color, and begin their lives as adorable frogfish.

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A male (red) painted frogfish (Antennarius pictus) trying to convince the female (yellow) to mate

Stay tuned for more frogfish insights coming in December, where I’ll write about the history of frogfish research and describe a handful of frogfish species, including a potentially “new” species. Until then, keep an eye for frogfish on all your dives, especially if you’re in warm water.

Poll: alternative muck diving terms

voteAfter the recent blog about the history of muck diving I received some interesting suggestions about alternative names to describe the activity. Because this is a democratic blog, it’s time for a poll! Tell me (and the rest of the world) which name you prefer and who knows, it might just catch on!

While less talked about than the term “muck diving”, a few people suggested the world needs a fitting name for muck dive enthusiasts (maniacs?).  In bird watching the most fanatic bird watchers are called “twitchers“. I reckon finding an appropriate term for those divers that love nothing more than finding new critters could be interesting.

I have been offered some suggestions, but feel free to add others. For the sake of inspiration, the name “twitcher” actually stems from the nervous behaviour of a well-known bird watcher in the 50s and 60s. So feel free to make fun of your photograph happy critter-enthousiast dive buddies 😉

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Muck-enthusiast in action (can you see the black hairy frogfish?

On the origin of muck diving

The last 3 years of my life have been dedicated to intensely studying critters and socio-economics related to “muck diving”. While this is a relatively common term in the scuba diving world, the vast majority of people haven’t got a clue what muck diving is. I can’t count the number of times people at conferences, meetings, drinks, etc. have gone: “You study what diving???”. Marine scientists seem to prefer hearing “Cryptobenthic fish assemblages on tropical sublittoral soft sediment habitats” than “Critters in the muck”. Each to its own I guess?

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Classic muck diving scene (Photo: Dragos Dumitrescu)

It’s not just scientists who are confused, a lot of divers have questions about muck, or at the very least are curious about how it started and where the name came from, so I decided to dig a bit deeper and find out some interesting facts about the origins of muck diving. If you have never heard of muck diving or just aren’t sure what it is, here is how I defined it in my last paper:

“Scuba diving in soft sediment habitats with limited landscape features, with
the explicit goal to observe or photograph rare, unusual, or cryptic species that are seldom seen on coral reefs.”

Or easier: Diving on sand/mud/rubble to find cool animals you don’t see on normal divesites. The word “muck” means either “Dirt, rubbish, or waste matter” or even worse “Farmyard manure, widely used as fertilizer”. In British English it is also used for “Something regarded as distasteful, unpleasant, or of poor quality”. I would guess that it’s the combination of the first and last meanings that inspired the people who started this type of diving.

Muck diving in its current shape has its origins in Milne Bay, Papua New Guinea. On a site called Dinah’s beach,  where Bob Halstead decided to try to do a dive on the site where their boat (the MV Telita) was anchored. The divers were skeptical at first as the site was mostly sand and did not look very appealing, but after discovering tonnes of creatures they had never seen before they were sold and muck diving was born. From its origins in Papua New Guinea, muck diving caught on and became popular across the world, but no place is as well known for muck diving as Lembeh Strait in Indonesia.

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Milne Bay, Papua New Guinea, where it all started

It is clear why Lembeh is famous with muck divers, as it really is a great place to dive and find some of the world’s most amazing critters. But how did muck diving in Lembeh kick off? What many people don’t know, is that Lembeh’s origin-story as the world’s most famous muck dive destination is pretty grim. The first resort in Lembeh (Kungkungan Bay Resort) was built in 1994, but the owners did not build their resort with critters in mind….

Back in those days, Lembeh was one of the best sites in the region to watch the big stuff. The plankton-rich waters of Lembeh Strait attracted scores of manta rays, dolphins, sharks,… Until 1996, when mankind showed just how destructive it could be. In March of that year, foreign fishermen came in and (illegally) installed the “Curtains of death”. These were huge nets, placed across the migratory routes of the large fish near Lembeh Strait. The nets were deadly efficient, during the 11 months they were used they caught:

  • 1424 manta rays
  • 577 pilot whales
  • 18 whales
  • 257 dolphins
  • 326 sharks (including whale sharks)
  • 84 turtles
  • many other animals including turtles and marlins

The original article about the curtains of death can’t be found online, but if you are interested, send me an email and I can send a copy. If you want to know more about destructive fishing in Indonesia, this is an interesting source start with.

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Peaceful Lembeh Strait has a turbulent history

The numbers are staggering, and for the few tourism operators in the area it must have been quite a shock. Until they discovered that Lembeh had much more to offer than just the big stuff. While there are no records of it, the story goes that muck diving in the area only properly got started when people started looking down at the sand instead of up at the manta rays. It makes me wonder what the area would have looked liked otherwise, and if muck diving would exist in the way it does now…

As it is now, muck diving is big, it attracts divers from across the globe and new critter hot spots keep on being discovered far beyond from where it all started. It’s exciting to think about how much more we will discover in the future! For me, one of the changes I would like to see, is the actual term “muck diving”. The name coined by Bob Halstead stuck, but I think most people in the diving (and academic) world agree that it isn’t really the most inviting name. I’d like to hear your suggestions (below in comments) on more suitable names for this type of diving and the divers doing it. If I get enough suggestions, I’ll organise a poll later to see what is preferred by divers around the world!

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It’s all about finding the small stuff – baby Painted frogfish (Antennarius pictus)

PS: Originally I wanted the full title of this blog to be “On the origin of muck diving by Means of Photographer Selection, or the Preservation of Favoured divesites in the search for Critters”. But the long title might have put off those readers who didn’t immediately get the very nerdy biology pun.