New publication: Fluo frogfish lures

After a weekend looking for vagrant fish in the cold waters of Shark Bay (more about that later this week), I came home to find a pleasant email in my inbox. A new publication has been published online last week. This one is in the journal “Coral Reefs” and is about biofluorescence in the Striated Frogfish (Antennarius striatus), more commonly known as the Hairy Frogfish. The article can be found here, but is restricted access. For those of you who cannot access it, here is what it is about.


Hairy Frogfish by day. Photo: Luke Gordon


As I have written previously, I have been doing a fair bit of work looking at biofluorescence in fishes. During these surveys i had noticed something strange going on with the Hairy Frogfish: their bodies are not fluorescent, but their lure is (very strongly). As you might know, frogfish use their lure as a fishing rod, attracting small fish closer, which are then eaten whole. The fact that the Hairy Frogfish’s lure alone is fluorescent but their bodies are not, hints at the possibility that this fluorescence could be used in what is called “aggressive mimicry”. Aggressive mimicry is the term used for animals who pretend to be something harmless (the “model”) and use that to get close enough to eat their prey.


Hairy Frogfish (Antennarius striatus) with fluorescent orange lure

But the question was, what would it be trying to mimic? Are there animals out there that resemble this fluorescent lure? Cue my last Philippines trip. During a nightdive with the unparalleled science hobbit, we found three more Hairy Frogfish (with fluo orange lures). More importantly, we also found a lot of freeswimming worms near them. Most of them a similar size as the lure of the frogfish, AND the same colour fluorescence as those lures. The resemblance between the lures and the worms went further than just size, shape and movement, but also the fluorescence is imitated. We found our model species!


Fluorescent worm (top orange squiggle) and fluorescent lure (bottom orange squiggle)

This is very exciting, as it is the first time anyone found strong indications that biofluorescence might be used to help fish catch prey. To prove whether it is really used to hunt, lab experiments or extensive observations would need to be done to check if this fluorescence really makes a difference. So while this is a very exciting glimpse into an unexplored part of hunting strategies in the ocean, much more work needs to be done to understand all the details.

If you can’t access the article but want to read it, or you just want to know more, send me an email or ask in comments and I can send the publication to you.

Critters in the cold


Squid during nightdive in Camp Cove (Photo: Greg Lecoeur)

I have been back in Perth for well over a month now and it had been close to two months without diving, so I was starting to get anxious to get back in the water. I don’t really have the time to go abroad at the moment, so I jumped on the opportunity to do a short trip to Sydney. A good friend (Greg Lecoeur) had an extended stopover before flying to Europe and asked me if I wanted to join him to find and photograph the elusive Weedy Seadragon (Phyllopteryx taeniolatus). Not only would it mean interesting dives, it also gave me the opportunity to catch up with another friend (the amazing Emma Camp) who does some great research at the University of Technology Sydney. The departure of the trip was a bit rushed but I managed to bring everything, except for my actual camera. Luckily both Emma and Greg are great underwater photographers, so I could enjoy the dives and get better pictures than I could ever take of them, win-win!

The waters around Sydney might be a lot colder than what I am used to, but they do offer some sweet diving and a lot of really interesting critters. The best known and most sought after critters in temperate waters in Australia are without a doubt the Seadragons. Seadragons are endemic to Australia (=found nowhere else) and only live in its southern, colder waters. Two species exist within reach of divers: The Weedy Seadragon (Phyllopteryx taeniolatus) and the Leafy Seadragon (Phycodurus eques). We went looking for the Weedy Seadragon, as the leafy variety is only found further south. I had been told where to look and that there were a lot more interesting critters to find, but when looking for critters it’s always a good idea to have a local guide. Through a friend I got in touch with a very keen local diver who knows the waters around Sydney better than anyone. Andrew (check his site here) kindly offered to take us diving and promised us dragons and much more.


Checking out a gorgeous Weedy Seadragon (Photo: Greg Lecoeur)

Our first dives were in the southern part of Botany Bay, Kurnell is known as one of the most reliable spots for seadragons. After the shock of hopping in 16 degrees cold water (I’m used to nearly double!) I managed to have a look around and appreciate the site. Descent visibility, kelp, rocks, sand and critters, what more do you need? After a mere 15 minutes Andrew delivered on his promise and showed us a beautiful seadragon. We would find a total of 7 that day! They really are amazing and stunningly beautiful animals. While they are related to seahorses and pipefishes, they are still very different. They are quite a bit larger and seem to be the result of a crazy drunk night between pipefishes, seahorses and some strands of kelp. Our presence did not seem to bother them at all, most of the ones we saw were happily pretending to be kelp and didn’t even stop feeding when we came in close for a good look.

Pygmy pipehorse

Find the critter, a Sydney Pygmy Pipehorse (Photo: Greg Lecoeur)

We found some other members of the seahorse/pipefish family that day. Besides a Potbelly Seahorse (Hippocampus abdominalis), Andrew also showed us some Sydney Pygmy Pipehorses (Idiotropiscis lumnitzeri). I was under the impression Pipehorses were a tropics only kind of family, but was happy to be proven wrong. This particular species is only found in the greater Sydney area, but is closely related to the ones I was observing in Dauin and Lembeh. They are at least as beautiful as their tropical cousins and in my opinion a lot braver for spending their days in the cold water. That cold water made Emma and me cut the second dive a bit short, diving in Sydney is all fun and games until someone gets hypothermia.

Pyjama Squid

The beautiful Pyjama Squid (Photo: Greg Lecoeur)

Our second dive day started at Bare Island. I only went for a short dive, but saw 3 juvenile frogfish! What’s more, they were Painted Frogfish (Antennarius pictus), which I also (wrongfully) assumed to be found in the tropics only. It’s funny how after nearly two years of studying critters there is still a LOT I can learn about them. That evening Greg and me went for a night dive at Camp Cove to find a little guy I had been dying to see for years, the Pyjama Squid (Sepioloidea lineolata). The site is a pure muckdive: a calm bay, no structures to speak of, just sand with a smattering of seagrass and some bits and pieces of debris. Needless to say I had a great time in that kind of environment, as would any other diver who likes critters. We found nearly a dozen Pyjama Squid, the first one about 20 seconds after we put our heads down! They are the cutest little things and pretty much nothing is known about them, I might have to consider them for my next project 🙂  We also found a lot of other critters: Bobtail Squid, a juvenile Hairy Frogfish, Toadfish, Bottletail Squid,… Basically everything a muckdiver could want.

Conclusion: Sydney is a sweet place to dive, both for muck and other kinds of diving. But beware of the very real risk of hypothermia (as Emma can attest to), especially if you are doing long dives and not moving much. So bring your warmest wetsuit, tea/coffee for surface intervals and most importantly, don’t forget your camera!


Black sand: Origins

The species I study are found in a very specific habitat. Unlike many (dare I say most) marine biologists who work in the tropics, I hardly spend any time at all on coral reefs, mangroves or seagrass beds. I estimate that since starting my PhD, roughly 80% of my dives were done over sand. No coral, no rocks, hardly any distinctive feature at all, just wide expanses of sand. Mind you, not just any kind of sand, the critters I look for seem to be found most often on black sand.


A black sand beach in Lembeh Strait, Indonesia

For those who have never had the pleasure of diving over black sand or those used to diving in places like Egypt, Maldives or the Great Barrier Reef, the idea of a black sand beach or dive site might seem strange or hard to imagine. When reading the words “tropical beach”, most of us imagine powdery white sand, turquoise water, and a bunch of palm trees added for good measure. But I am happiest starting my dive from a beach as black as my (soul) wetsuit and dive boots. The first time you see a true black sand beach is mesmerising and even a bit alienating, it somehow doesn’t seem right. The water looks grey instead of blue, darker, and less inviting than those beautiful blue lagoons from travel brochures. Until you put your head under water and start looking around…

But why are some beaches black? What is the difference between the powdery white sand of Maldives and the pitch black sands of Lembeh or Hawaii? After the ICRS conference in Honolulu last week I decided to go have a closer look at the origins of my preferred study systems: active volcanoes! There are few places on this world better suited to do this than on Hawaii’s big island. Accompanied by Jamie, a marine scientist specialising in underwater soundscapes, I set off to find out how close to a volcano one needs to get before the hairs on your legs get scorched off 😉


Lava flow making its way through the forest

Turns out the answer is: not very close at all. In what was the highlight of our trip we flew in an open-doors helicopter over a lake of magma and a lava stream running down a mountain. Even hovering 50m above the lava you can feel the incredible heat emanating from the stream! The Kilauea volcano is one of the most active volcanoes in the world, and has been erupting since 1983. The result is an amazing landscape of solidified lava, covering vast expanses of the island.  During our 3 day stay in the Volcano National Park, we visited lava tubes, hiked over solidified lava lakes, were awestruck by the raw spectacle of watching a volcanic crater at night, and got sunburned ambling across a frozen lava wasteland that was a village until only few year ago. While we were in Hawaii, there were no lava streams entering the ocean, but there were plenty of places where it recently did.


Fresh lava flow in the ocean

Liquid lava flowing in the ocean is one of the two ways black sand beaches can be formed. The lava is so hot that when it runs into the cold water, it causes explosions that shatter tiny fragments of volcanic sand/glass around. This process can happen so fast that a black sand beach can be formed overnight! The size of these fragments can be from small boulders to actual fine sand, dependent on the temperature of the lava and the water. The dark colour of the sand is caused by the mixture of minerals inside the lava, the minerals giving the darker colours are mostly iron oxides such as magnetite.

The other way black sand beaches are formed, is through erosion of black volcanic rocks by rivers, which then carry the black grains of sand down to the ocean. Depending on which other types of rock the rivers flow over other minerals will be added to the mix, resulting in sand colours that can range from pitch black to dark brown or even beige or green. For any geology-inclined readers, this site has got all the details you could possibly want to know about black sand.


Black sand + dive boots

So to summarise: black sand ecosystems are formed by some of the most epic geological processes in the world, magma from the centre of the earth erupting and shaping the world as we know it. The powdery white sand beaches of Maldives on the other hand, are mostly formed by the build-up of whole lot of parrotfish poop***. An interesting process for sure, but give me an epic black sand beach over a pile of fish poop any day 😉


***Technically speaking parrotfish poop, eroded corals, shells and bits of other stuff, but I’m taking some freedom here 😉

Ethical issues in Underwater Photography

During my PhD I have written and talked a lot about the value of scuba diving and particularly of muck diving. Dive tourism often provides an income to communities who have limited sustainable alternatives to make a living. Over the last years, there have been big changes in dive tourism, such as the increasing popularity of underwater photography. Muck diving in particular has a large portion of divers who use underwater cameras: I found out that on average 73% of people visiting muck dive destinations use a camera of some sort.

More people using cameras underwater can be a good thing. Photographers often spend more time and money in dive locations, meaning a higher income for local communities. Having a lot of photos taken underwater can directly help science by giving us information about species distribution (via initiatives like iSeahorse) or even by helping researchers discover new species (the story of the “Lembeh Seadragon“). Finally, more beautiful photos of ocean critters can help conservation by creating awareness with people who would otherwise never go near the ocean.

Kyonemichthys rumengani

The “Lembeh Seadragon” (Kyonemichthys rumengani) was first brought to the attention of scientists by underwater photographers.      Photo: Maarten De Brauwer

However, there are some serious issues with the use of cameras under water. Using an extra tool while diving is distracting and often leads to poor buoyancy control. Multiple studies have looked at the effects of divers who use cameras on coral reefs, and it is very clear that photographers cause more damage on coral reefs than divers without cameras. Possible solutions for this problem include buoyancy training, good dive briefings that create awareness with the divers, and attentive dive guides who can adjust diver behaviour before too much damage is done.

Another problem with underwater photography is that it is a goal-driven and therefore often competitive activity. Photographers want to see rare species, shoot interesting behaviour or get a unique shot that will impress fellow divers in off- and online communities. But the reality is that rare species are hard to find and often really shy. You have to be lucky to observe eye-catching behaviour and it takes a lot of skill to get creative shots underwater. The desire for beautiful pictures too often leads to divers trying to “force” a photo to happen, and forcing wildlife is never a good idea.

This is not just an issue with underwater photography, it happens on land as well. In 2010 a Wildlife photographer of the year lost his title when it became clear he faked his winning shot. In India, the bad behaviour of tourists trying to take pictures of tigers has led to the creation of a guidebook for ethical wildlife photography. There are worse stories out there and this article explains just how bad “getting that perfect shot” can get.

Underwater wildlife photography has its own specific problems. Unlike terrestrial photography, divers can often get within touching distance of the species they want to photograph. At that point it is often very difficult to resist the temptation not to touch or harass the animal. There are many reasons why you shouldn’t, and you’ll find most of them explained clearly here. Luckily most fish, especially the bigger species like sharks or manta rays can swim off when things get too crazy, but this doesn’t work for all ocean critters.

Animals that cannot swim away because they are too slow or rely on camouflage instead of speed, are popular with photographers because you can take your time for a picture. Frogfishes, seahorses, nudibranchs, scorpionfishes … never had to cope with humans and cameras, so they don’t have any defence against them. Some of the poor diver behaviour I have seen seems relatively harmless, like gently coaxing an animal in a better position. But it can go as far as smacking Rhinopias around to daze them so they will sit still, pulling of arms of feather stars to get pictures of the fish living inside them, or breaking off seafans with pygmy seahorses on them and bringing them up to shallow water so divers can spend more time taking pictures. In these extreme cases, diver behaviour can lead to serious harm or even the death of rare animals.

Froggie yawn

Pictures of interesting behaviour like this yawning frogfish (Antennarius commersoni) are popular, but the yawn might actually be a sign of distress.

To a large extent it remains unknown what the effects of diver manipulation are, though it is clear to see that it at the very least stresses animals. I am currently working on a project to find out which negative diver behaviours around critters are most common and how it effects the animals. The goal is to enable the dive industry to focus on preventing the behaviours which have the highest impact.

While most divers don’t approve of this unethical behaviour, industry leaders like organisers of photo competitions or dive centres still seem reluctant to admit there are serious ethical issues in underwater photography. Maybe out of fear of giving underwater photography a bad name, or out of fear to make less profit when strict rules are applied. What we need is a change in mentality from divers and industry leaders. Well known photographers like Dr. Alex Tattersall and Josef Litt are increasingly making themselves heard to set the right example. Organisations like Greenfins work closely with dive operators to improve destructive dive practices. A lot of this unethical behaviour can and will disappear with the support of divecentres, dive magazines and role models from the underwater photography community. So if you enjoy taking pictures underwater, consider signing this petition that asks for higher ethical standards in dive magazines and photo competitions.