New publication: Parasites on the Great Barrier Reef

This is blog is a story about more than just a new publication, it is also the story of how I became a full time marine biologist. The publication might have come out only last month, but its story began more than 5 years ago on an expedition site in the Philippines…

It is on that site where I met my good friend Eva, who asked me at the end of the expedition if I wanted to join her on the Great Barrier Reef (GBR) for a couple of months of fieldwork. At that point I had no idea that we would be studying cleaner wrasses and parasites, but who would say no to such an offer?

Male adult Gnathiid parasite

A male gnathiid parasite

So November 2012 found Eva and me in a tiny plane, on our way to Lizard Island while  enjoying the amazing views over the GBR. The fantastic research station on Lizard Island would be our home for more than three months while we were conducting a series of experiments designed by Dr. Lexa Grutter, one of the world’s experts on cleaner wrasses and fish parasites.

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Lizard Island in the Great Barrier Reef

The experiments we were doing are part of a much larger project that’s been ongoing since the year 2000. The base of the project are 16 small patch reefs, half of which have had their cleaner wrasse removed from the start of the project, and the other half was left alone. To make sure the “removal reefs” stay cleaner wrasse-free, they are regularly checked for new cleaner wrasse, which are removed when found. This amazing setup makes it possible to see how reefs without cleaner wrasse are different from reefs with cleaner wrasse.

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Eva and one of our “Hemis” (Thicklip wrasse / Hemigymnus melapterus)

Our particular experiment was designed to test if the number of gnathiid parasites (basically the mosquitos of the sea) were different when there are no cleaner wrasses on a reef. Cleaner wrasse eat the parasites off fish, but it’s unclear if they eat that many that it has an effect on the total number of parasites on coral reefs. The best way to count parasites is by using living fish as bait, Eva and me used the beautiful thicklip wrasse (Hemigymnus melapterus – aka “Hemis”). Our lovely hemis were put in traps which were placed on the different reefs for 12 hours. The traps are specifically designed containers that let the smell of fish out, and would allow parasites to enter, but not to escape.

We did two main sampling periods, each three weeks long, centered around the full moon. During sampling, our daily routine was to get up well before sunrise, collect the fish that were put out the night before, and deposit a new batch of fish. The main part of the day we would collect the parasites from the traps, and tend to our Hemis and their aquaria. At sunset we would collect the morning traps + fish and deposit a new batch of traps + fish. The days ended with collecting the daytime parasites. I can say in all honesty that I haven’t done such a tiring, but simultaneously exciting fieldwork experiment since.

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The end of a big experiment: time to celebrate!

The work we did provided only half of the data, more data was collected from similar experiments conducted by other colleagues, using different fish species. Afterwards there was a lot of lab work done by yet other collaborators, who counted and identified all the parasites. Only then could the data by analysed and written up. Sometimes experiments are quick and easy, sometimes they take a massive team effort!

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Parasite trap on the reef

So the results are in now, and they are very cool. The main story is that when cleaner wrasse are present on a coral reef, they indeed have an effect on how many parasites infest fishes. But… The effect only happened by day, and only for big fish species such as our thicklip wrasses. For smaller fish species like damsel fish, there was no difference whether or not cleaner wrasse were present on the reef. Also very interesting is that cleaner wrasse only have an effect on the parasites that are active by day.

 

What does this all mean? In short, it seems to indicate that cleaner wrasse not only directly remove parasites from fish, but they do it so efficiently that it keeps the parasite numbers down in the areas where they clean fish. This is in turn good news for all the other fish on the reef, as living in an area with less parasites is much better for your health than living in a place full of parasites. Just think about it, how much would you enjoy living in a mosquito-ridden swamp? This experiments shows that cleaner wrasse are at least partially responsible for removing the mozzies from your swamp!

This paper means more than that to me, it means very fond memories of tiring sampling sessions, crazy-pants parties, beach runs, sunset drinks, meeting some fantastic people,… But more than that, the work involved made me realise how much I enjoy doing research, and it is what made me decide to pursue a PhD in marine science. So being able to write a blog about this paper while I am in the final stages of writing up my PhD thesis very much feels like things have come full circle.

 

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New publication: Finding fluorescent critters

Great news! I can finally share the reason why I was playing around with fluorescent torches for the last three years. The main biofluorescence paper I have been working on was published two weeks ago in the journal Conservation biology, happy days!

Previously I have written blog posts about funky biofluorescing fish, publications on frogfish that might be using fluorescence to attract prey, or just some funky fluo pictures to keep you you entertained. This particular story is about why I started working on biofluorescence in the first place and how the results of the research might help to protect little critters.

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Biofluorescent painted frogfish (Antennarius pictus)

As anyone who has ever tried to find small or camouflaged critters during a dive will be able to tell you, the little guys are pretty hard to find! This isn’t just a problem for a dive guide who wants to show pygmy seahorses or small frogfish to his divers, it is also a very real and well-known problem for marine biologists trying to study them. Finding these “cryptic” critters might be a headache for divers, but there is much more at stake when you are trying to collect data about critters that might be endangered with extinction.

If you are trying to figure out if an animal is endangered, the obvious first thing you want to know is “how many of them are out there?”. All good and well when you are studying elephants or giraffes, but slightly more tricky when you’re studying pygmy seahorses or a tiny goby that’s less than 3cm long! Not finding any pygmy seahorses or gobies could just mean that you didn’t look hard enough.

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Biofluorescent moray eel (Gymnothorax zonipectis)

Scientists have three different ways of coping with this issue:

  • First option: Ignoring the problem by not counting small, cryptic animals when doing surveys. After all, if you weren’t looking it’s only normal you didn’t find any.
  • Second option: Adapting standard “visual surveys”. Usually by going slower or looking harder at a smaller area than when looking for big fish. This way you find more cryptic critters, but a lot still depends on how good a researcher is at spotting small fish.
  • Third option: (you might not like this one) Using chemicals that either stun or kill all the fish in a small area, after which all the fish are collected and counted. This method is very efficient and gives a good idea of which fish were living in that area. Unfortunately using methods that kill fish are not ideal, especially when you might be dealing with rare species.
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Two fluorescent seahorses (Hippocampus subelongatus)

This is where biofluorescence could come in to help. If you are confused about what biofluorescence is, definitely check out this post or this website. But briefly, biofluorescence happens when fish first absorb light and then reflect it in a different colour. Importantly, biofluorescence is  not the same as bioluminescence, where animals produce their own light.

So what has biofluorescence to do with finding cryptic fishes? A few years ago, a paper was published that stated that biofluorescence is common in camouflaged fishes. The work looked into evolutionary history, but the main idea triggered a little light bulb. I had previously seen coral researchers use biofluorescence to find baby corals (which are tiny, transparent, and VERY hard to see), so I wondered if the same technique could be used on cryptic fish.

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The same bandtail scorpionfish (Scorpaenopsis neglecta), with and without fluorescence

So I decided to test it as a part of my PhD. I was very lucky to get support from multiple divecentres which helped me to go fluo-diving all across Indonesia and the Philippines. In the last 3 years I did over 200 dives observing, investigating, counting, and cursing fluo-and non-fluorescent fish. The results are published here, but the answer is: Yes, you can use biofluorescence to count cryptic fishes.

The vast majority (87%) of cryptic fishes I tested showed biofluorescence, compared to a small fraction (9%) of the non-cryptic fishes. A cryptic fish is 70.9 times more likely to be biofluorescent than a non-cryptic one! When comparing normal surveys with fluorescence surveys, I found three times as many triplefins (a small cryptic fish species) when using fluo surveys than during comparable normal surveys.

What was also really exciting (to me at least) is that I discovered that pygmy seahorses are fluorescent as well! Using fluorescence I found twice as many Bargibant’s pygmy seahorses than without the fluo torch. As if they weren’t cute enough already, these little guys are fluo pink when you look at them with the right tools!

Fluorescing seahorses are not the only reason why I am excited about this new publication…although it probably plays a bigger role than it should in order to call myself a serious scientist 😉 The great thing is that this is an easy and cheap technique that could help researchers study and conserve small fishes more efficiently than before. And in the end, that’s what it’s all about for me, making sure the oceans remain an amazing place full of critters to enjoy looking at…

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Robust ghostpipefish (Solenostomus cyanopterus) are biofluorescent too!

 

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.

Fish nerds, critters, sharks and shirts

As I have written before, attending scientific conferences is an important aspect of working as a researcher. One of the benefits of being a marine scientist is that these conferences tend to take you to nice places (Hawaii for example), and this was proven once again at the 10th Indo-Pacific Fish Conference (IPFC), which just finished in Tahiti.

IMG_7936IPFC is the largest fish-focused conference in the Indo-Pacific region, and is held once every 4 years. This year was the 10th time it was organised, with more than 500 fish nerds scientists joining the fray. It is hard to explain to non-scientists just why these conferences (IPFC in particular) are such interesting events. They’re obviously good for learning about the newest research in your field, but it is also a great chance to catch up with old friends, or to meet the experienced researchers whose research you might know inside out, but have never actually met. It feels a bit like getting to mingle with the “celebrities” of the marine biology world. Besides celebrities and old friends, fish conferences are also THE BEST excuse in the world to whip out your finest/loudest fish themed shirts!

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Fish nerds rocking the fish-themed clothing at IPFC in Tahiti!

From a scientific point of view, some of my conference highlights were:

  • A big session with multiple talks dedicated to cryptobenthic fishes. It was fantastic to meet more people who study similar oddballs as I do, learn more about their research, and discuss important future research steps.
  • Hearing really bad news about how we are still overfishing most fish-stocks and how government subsidies make this problem much worse.
  • Then hearing good news on how well-managed marine protected areas have helped shark numbers in Australia recover from overfishing.
  • Plenty of new  and exciting developments in understanding the behaviour of fish larvae (I’m not even being ironic here, it’s awesome science, trust me!).
  • Learning more about why deep sea fishes look so weird and how their looks change with depth.
  • Thought-provoking questions on how to deal with oil and gas platforms in the sea after the wells run dry.
  • Finding out that parrotfish are a bit like hamsters, storing excess food in their cheeks while they’re feeding.
  • An important and super-interesting session that focused on women in marine science, which are (unfortunately) still underrepresented in our field.
  • The enormous kindness and willingness of experienced scientists to help and encourage the new generation.

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Squadron of blacktip reef sharks

Obviously while we were in Tahiti, we did more than just sit and talk about fish. We also went exploring to see what Tahiti had to offer and to find some actual fish. And oh boy, the fish we found!!! I might find a lot of very cool small critters for my research, but I rarely come across big sharks. During a shark dive just off Tahiti we saw 3 big tiger sharks, joined by a whole lot of other sharks for good measure. While tiger sharks are obviously not quite as interesting as small critters, they are impressive, awesome, and beautiful beasts! And while they get big (close to 4 meter), I did not feel worried about getting attacked at any point. They are undoubtedly top predators, but far from the monsters the media would like to make them out to be.

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Two tiger sharks and a blacktip reef shark

Besides sharks, we were also lucky to see humpback whales (from the boat), and went exploring on land. I’m sure you won’t be surprised if I tell you that Tahiti is a stunning place. Waterfalls all around, jungle, ocean, waves, super friendly people,… So you can imagine that this week I was mostly wandering around with a big grin on my face. On top of this, Tahiti is also a great place if you like tattoos, and I was very (very!) tempted to get a new one done here, but managed to stop myself. Only just though, so it’s probably a good thing that I am leaving tomorrow 😉

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Happy fish nerds exploring Tahiti’s beaches

So what next? I am writing up the last chapters of my PhD-thesis, so the search for new challenges (postdoctoral research!) is slowly getting started. There is more good news as well, an article on my biofluorescence research just got accepted in the journal Conservation Biology, so you can expect a new blog about that paper soon. But before that, a new guestblog is coming up that delves deep into the world of frogfishes…

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View over Moorea