Thinking about sand and the fish (and researchers) that call it home


Why would you study pretty fish on coral reefs if you could be trying to find grumpy weirdos like this Painted frogfish (Antennarius pictus)

Maarten De Brauwer is a marine biologist, dive instructor, biology teacher, PhD-candidate at Curtin University in Perth (Western Australia) and studies fish on soft sediments is lucky enough to work on sandy habitats  ;). He also does a really nice job on the science communication front over at Critter Research!  Below is his guest blog with some recent musings…

Thinking about sand and the fish (and researchers) that call it home

When I was asked to write a guest blog I first considered writing about fluorescent frogfish or about how weird fish that live on the sand can send children to school in developing countries. While I might do that another time, instead I decided to start a guest blog for Fish Thinkers by thinking about fish. Maybe because thinking about fish is what I am currently paid to do, though the fact that I’ve gone through 3 gin tonics and a fair amount of wine on a long-haul flight might play a role too.

Like Lachlan, I am also doing a PhD in marine biology, also like him I am fascinated by the fish that are found on sandy bottoms (or “soft sediments”). Regardless of how we got to where we are (an interest in fishing, diving or photography), the largely unstudied fishes that live away from pretty (coral) reefs and spend their days playing in the sand are what makes us tick.


Departing for fieldwork on a black sand beach in Lembeh Strait, Indonesia.

Unlike the usual posts on this blog, my system is not the temperate Australian oceans. I spend the majority of my fieldwork in the balmy seas of Indonesia and Philippines. Unlike Australia, there are hardly any recreational fishermen in Southeast Asia. Instead people either use sandy areas to get fish to feed their family, or increasingly often people visit to photograph funky looking fish (the so-called “muck diving”). When people imagine diving in the Coral Triangle, they tend to picture vibrant colour reefs filled with clownfish, turtles and other well-known characters from Finding Nemo/Dory. The reality is that most of the coral triangle area is made up of sand. Not coral, not seagrass, not rock, but sand (or “soft sediment” if I may).

This fact never ceases to amaze me, most of what is known as the world’s largest coral reef system is in fact sand. Undoubtedly, there is a lot of coral around and I can personally attest the reefs are amazing to see. Diving the reefs of Raja Ampat will blow even the largest cynic’s mind (it did mine). But to me, the fact that a large proportion of the coral triangle area receives hardly any attention was so intriguing that I have now spent close to three years studying nothing else. There are some very valid reasons why coral reefs get the bulk of the attention; they are some of the most biodiverse regions in the world, they are beautiful, provide many crucial functions for humans, etc. But what about the sand?

Well, there is some good and some bad news. The bad news is, we don’t really know what is going on. We don’t really know how the system works in the tropics, the ins and outs of the food chain, the life cycles of fishes, even what fishes live there. New species are often described, after which the research usually stops. For most species on the sand we don’t know what role they play in the ecosystem, or how it relates to coral reefs or other habitats such as seagrass meadows. The information we do have tends to come from fishermen trawling the ocean and coming up with a bunch of dead fish.


Fish living on the sand like this Lizardfish (Synodus sp.) often show biofluorescence

The good news is, slowly but surely we are finding out more. What at first sight seems to be a barren desert, turns out to have incredibly diverse and well adapted fish communities living in it. Small changes in what the sand looks like or is made of can drastically affect of what lives here, and turns a dive in the desert into an almost extra-terrestrial discovery experience. Something dive operators had picked up on over a decade ago, and science is starting to get in on too.

Some of the few exciting things I have learned about soft sediments over the past few years include:

  • Frogfishes might lure prey using biofluorescence
  • There are still many undescribed species out there
  • Thousands of people make a sustainable living by taking people diving to find critters on the sand
  • Many species thought of as “rare” might actually be much more abundant if you just look in the right places.

Species like this Mimic Octopus (Thaumoctopus mimicus) might be a lot more common than what was previously assumed

Amongst all the bad news we keep on hearing about the oceans, these are things that simultaneously make me happy and worry me. The oceans are even richer and more complex than we can imagine, but at the same time, we might be losing more than we realise. Which is why it is crucial that we keep on doing what we are doing, and probably even more importantly, that we tell the world about it. You might be right in thinking that us soft sediment scientists are “special” for being so interested in sandy fish, but we’ll be damned if that will stop us. Quite the opposite, we will keep on telling you how interesting sand is until you start believing it and become a fish thinker yourself.

If you want to know more about the research I do, have a look at or visit Researchgate to have a look at publications. If you’re just into nice pictures or short bits of information, check out critters research on Instagram or Twitter.

5 thoughts on “Thinking about sand and the fish (and researchers) that call it home

    1. Maarten De Brauwer

      Hi Margie,
      they actually do, in places like Lembeh Strait (Indonesia), or Dauin (Philippines), muck diving creates jobs that increase welfare of local communities. With as a direct result that parents can actually afford to let their children spend more time at school than helping out with fishing/farm work. Granted, this isn’t a widely applicable solution for poverty, but it makes a huge difference in the lives of thousands of people. I’m finishing up a paper about this as we speak, so hopefully I can share the full story early next year!



  1. Pingback: GOOD LUCK

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