Using SMURFs to catch baby fish

Luke and I have been in Dauin for a few days now. We are here to investigate the recruitment of cryptobenthic fish. If you’ve read this blog before, you’ll know that I am interested in camouflaged, small critters that live on the seafloor (=cryptobenthic). You might not, however, have heard about “recruitment”. This is the term used to describe the process of larval fish (which usually swim in the open ocean) “settling down” on the reef. When fish larvae settle, they change rapidly from small, transparent, weird oddballs to colourful reef fish. Or in the case of the critters I study, to camouflaged weird oddballs.


Larvae and adult Sargassum Frogfish (Histrio histrio) Source:

There are many reasons why I would like to know more the recruitment of the species I study. The most important one is that nobody really knows why some of these baby fishes show up where they do. If you don’t know this information, it is really hard to protect the right places that would be a suitable habitat for baby fish. Another reason is that this process is vastly different from anything we see on land, making it fun and challenging to try and figure out what is going on.

So how does one best study tiny baby fish? In the case of my critters, looking for the small adults is already hard, so how do you even begin to try and find the even tinier versions? The slightly disappointing answer is: “We don’t really know”. There are multiple techniques to find new recruits or larvae that are about to settle down (light traps, visual surveys, crest nets, …). But most of those don’t seem to be very effective for camouflaged critters. One method did show promise in a study in the Caribbean, the benthic “SMURF”.  If at this moment you are imaging little blue creatures with scuba tanks, catching baby fish with lassos and you don’t want to spoil that mental picture, please stop reading now.


SMURF at sea (Photo Luke Gordon)

Since you’re still reading, I can now disappoint you about my SMURFs, they are not the ones you have seen on tv (no ethics clearance possible). SMURF stand for “Standard Monitoring Unit for Recruitment of Fishes”. It is a mesh-basket you fill with any substrate you want (pebbles, sand, coral rubble, plastic,…) which you then place in the ocean for a set time. After that time you collect the basket and see how many baby fish were attracted to your unit. Not quite the blue man-option, but you are the one who kept reading.

Luke and me made a whole bunch of units, which we deployed around Dauin. To deploy the units we had the help from my supervisor Euan Harvey, who decided to drop by to see what we are up to in Philippines. Euan is an expert in remote sampling using video cameras, but he definitely seemed to enjoy setting up experiments on baby critters as well. This could be due to the fact that on his very first muck dive here, we found Flamboyant cuttlefish, Blue-ringed octopus, a bunch of Frogfish, Ghostpipefishes, Seahorses and loads more critters.


Euan photographing Ghostpipefish (Photo Luke Gordon)

This is the second time I am trying this experiment, the first attempt was thwarted by the ocean. Conditions are looking better now, so with some luck the units will survive the next weeks. By the end of the SMURF-project, we will hopefully know if this method  works well for the species I study. With some luck, I will even be able to tell you if baby cryptic fish prefer sand, pebbles, or rubbish. The method can then be used in the future for other people wanting to study the recruitment of cryptic species, so we can start to unravel some of the bigger questions about these poorly studied animals.

Divers and Seahorses: ADEX

Last week I had the pleasure of attending the annual ADEX Dive Expo in Singapore. If you want to find out what scuba diving is about, or want to realise what a big deal it is, this is the place. Just to give an indication of the growing interest in diving: the expo received close to 60 000 visitors in 3 days! Besides the many stands from dive centres, resorts, photography shops, etc. who were trying to convince people to buy dive trips or equipment, there was a lot more to see and do. Throughout the weekend, there were non-stop presentations by marine biologists, NGOs, photographers, writers and even mermaids.

This year’s theme was “Seahorses“, so some of the world’s seahorse experts such as Dave Harasti, Amanda Vincent and Richard Smith were around to talk about these funky critters. There were speakers from the Coral Triangle Initiative, Greenfins, iSeahorse, Blue Ocean Network and many more NGO’s. It wasn’t possible for me to see them all, but I saw enough to learn a whole lot of new interesting things about seahorses and their conservation.

I was quite honoured to have been invited as well to give two talks. I talked about fluorescence in camouflaged species and how valuable muck diving can be to small coastal communities. From the chats I had with people afterwards, it seems I wasn’t talking absolute nonsense and people were actually interested in what I had to say. While it is too early to tell, in the future there might even be some interesting projects coming out of these meetings.


Explaining the value of Muck Diving

The most interesting facts I’ve learned this weekend? It seems seahorses often end up as prey for frogfish, scorpionfish and even the occasional octopus. This is also the reason why successful marine protected areas with lots of predators might lead to less seahorses in those protected areas. I’ve also noticed once again that there is more and more demand for truly sustainable dive tourism in a way that really benefits local communities and not just the owners of dive resorts.

Spending a few days in the comfort of modern Singapore was nice, but now it’s time to get back to work. And for now work = fieldwork!  😀 Yesterday I arrived in Dauin accompanied by none other than Luke, my very good friend and trusty science hobbit! Keep your eyes on the blog for our adventures looking for baby critters…

New publication: For clownfish sharing means caring

Best of Bali_Clownfish and Periclemens shrimp_MDBWhile I am currently immersed in an amazing project investigating muck critters, I have done research on more conventional fish in the past. One of those conventional fish, is the ever popular clownfish (aka “Nemo”). Clownfish might not be quite as amazing as Frogfish or Rhinopias, but they are pretty interesting and funky fish nonetheless.

Last week the research I did 2 years ago in Wakatobi got published. When I write the research “I” did, what I really mean is the research my good friend Emma Camp and me did with the help of a great bunch of people of Operation Wallacea. Besides these great people, there were some terribly clever people from the University of Essex and Curtin University who helped to make this a really neat paper. If you are interested, you can find the paper here,  but I’ll assume you haven’t got much time so here is the short version of what we found out.

As you probably know, clownfish live in anemones. What you might not realise is that there are 28 species of clownfish and only 10 species of anemones that can be used as a “host” (aka house). Usually you’ll only find one species of clownfish per host anemone. In places where lots of different species of clownfish live, you would expect a fierce competition for their hosts. But what we found in the Coral Triangle, is that clownfish instead share their hosts. The higher the diversity, the more often clownfish share their host anemones. What this means is that house sharing helps to create and sustain the high diversity we find in the Coral Triangle.


Amphiprion melanopus (large fish) and A. perideraion (small fish) sharing an anemone

What is more, the species that shared their anemones were less aggressive towards each other than in anemones with only one species. This is probably because different species don’t have to compete over mates or (in some cases) over food, a win-win for all fish involved. After all, anyone who ever shared a house knows it’s easier to get along when  you don’t steal each other’s food or partner.

If you want to read more about this research, you can have a look at the media release or this summary. Or you can ask me whatever you want about it in comments below, certainly in case you can’t access the original paper. I’m planning to add a publications section to this blog in the near future, so stay tuned.


Amphiprion melanopus (large fish) and A. perideraion (small fish) sharing an anemone