research

New publication: Fluo frogfish lures

/ Maarten De Brauwer / 4 Comments

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.

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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.

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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!

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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.

Black sand: Origins

/ Maarten De Brauwer / 9 Comments

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.

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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 😉

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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.

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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.

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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 😉

Coral Reef Conference in Hawaii

/ Maarten De Brauwer / 7 Comments

The International Coral Reef Symposium (ICRS) in Hawaii has come to an end. While I am using the opportunity to explore more of Hawaii, I figured it could be interesting to share some of the highlights. ICRS is a huge conference held once every 4 years, with about 2500 marine biologist gathering together for 5 days of presentations, workshops, poster sessions, networking and socializing. To give you an idea of just how much research was being presented: for 5 days straight up to 10 differently themed sessions would run at the same time. Session themes were very diverse, from reef fish ecology to the role of macro algae, to protected area management, genetic connectivity, effects of pollution, etc.

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The very shiny conference centre

With literally more than a thousand interesting talks going on simultaneously, the hardest thing was choosing which ones to go see. Unfortunately, though not surprisingly, there were very few talks about cryptic critters (3 to be precise), but there were plenty of other really good talks to see. So here is an overview of a few talks that stuck in my mind.

One of the plenary talks was to hand the the Darwin medal to Jack Randall, this medal is awarded once every four years in recognition of major scientific contributions throughout the career of a coral reef scientist. Most people reading this blog won’t know Jack Randall, but on his own he described more new species than any other fish taxonomist ever did. In other words, an absolute legend in the world of fish taxonomy. It was inspiring to hear him talk about his long career and to see how passionate he still is at the age of 92!

Another talk that stuck with me was a talk on cryptobenthic fishes (small fishes) living on coral reefs. Chris Goatley‘s research showed how important it can be for small fish to grow even the smallest bit. A difference of only 1mm can increase their chances of survival massively. Size however is not the only factor that helps them survive, for these small fishes, the most important thing seems to be experience. In other words, a fish of 2cm that is 2 months old has a much higher chance of surviving than a similar sized fish of 2 weeks old. Which proves that you can forget about that 3 second fish-memory myth as well.

Miss Baldisimo from the University of Philippines talked about the aquarium trade, a hot topic now that Finding Dory is out. The trade usually does not get much attention but it is still massive, and Philippines is the biggest exporter of marine aquarium fish globally. What was new to me, is that in some areas fishermen are starting to specialise in collecting frogfish! Unfortunately there is still massive overfishing and high mortality of the fish during catching and export. What makes this even more tragic, is that the fishermen are very poorly paid for their hard work, the price per fish has not increased in over 20 years! So think twice before you want to get a marine aquarium.

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Clownfish in trouble? (Picture: Greg Lecoeur)

Also connected to Finding Dory, was a presentation about clownfish in the Red Sea. Researchers have noticed a huge decline (86%) in host anemones in the  gulf of Eilat. This has lead to a similar decline in Red Sea Anemonefish (Amphiprion bicinctus) and might even lead to a local extinction if this trend continuous. The researchers could not find the cause of this decline, which is particularly worrying. Luckily the species is very common in the rest of the Red Sea, so there is no immediate threat for the species as a whole.

 

I had the pleasure of watching the talk of a blogger I had been following before the conference even started. Jobot turned out to be someone I had actually already met a few years ago during fieldwork in Lizard Island. For her very cool project she used acoustic trackers to see when reef fish died or got eaten.  One of the most surprising results she found, was that most predation (fish being eaten by bigger fish) happened during the day and not at night! Sunset and sunrise were even more intense, which has been assumed for a long time, but the fact that less fish get eaten at night was a surprise for most people attending the talk.

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Discussing fluorescence in fish

During the conference I presented a poster about the fluorescence research I have been doing the last year and a half. It seems that the poster was well received, as I got the student prize for the best poster during the conference. I am still not sure what I actually won since I was not present at the last plenary talk, so still some mystery in the aftermath of the conference.

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Chilling out at HIMB

The day after the conference I was lucky enough to be able to visit the Hawaii Institute of Marine Biology (HIMB). HIMB is a world class research station located on a small island at the northeast coast of Oahu. Besides being a place where awesome science is done, they also had hammerhead sharks in their big enclosure, and seeing hammerheads is always a treat 😉

 

In short: I had a great time at the conference, not only because of the science but also because I got to meet up with old friends and meet a lot of great new people. The next few days I am off to do some volcano exploring on the Big Island in Hawaii, before heading back to Perth for some more serious sciencing!

 

Ethical issues in Underwater Photography

/ Maarten De Brauwer / 11 Comments

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.

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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.