The plight of Tasmania’s handfish

March 1, 2021March 2, 2021 / Maarten De Brauwer / 3 Comments

The cold waters of Tasmania might seem like a far cry from Indonesia’s treasured critter-dive locations, but for those willing to brave the cold, they hold some amazing treasures. Put on your drysuit, grab your camera, take the plunge, and you just might discover some of the rarest fish on the planet.

Tasmanian dive sites are home to seadragons, multiple seahorse species, but the critters that will convince me to shiver my ass off are the handfishes. Handfish are relatives of the better-known frogfishes, which means to have a similar fishing lure (adapted dorsal fin spines) on top of their head. As the name implies, they also have adapted pectoral fins which resemble hands. Like their frogfish cousins, handfish spend most of their life on the seafloor, waiting for unsuspecting prey to swim by and gobble up.

There are 14 known handfish species, all of which are found only in southern Australia. Unfortunately, 8 out of the 14 species are endangered. One species, the Smooth handfish (Sympterichthys unipennis) even has the unfortunate distinction of being the first marine fish to have gone extinct.

^{What a fish! The red Handfish (Thymichthys politus) is critically endangered. Photo credit: Tyson Bessell}

Other handfish species are not doing much better and might follow in the Smooth Handfish’s unfortunate footsteps all too soon. The Red Handfish (Thymichthys politus), Spotted Handfish (Brachionichthys hirsutus), and Ziebell’s Handfish (Brachiopsilus ziebelli) are all considered to be Critically Endangered. The fate of the Ziebell’s handfish in particular is looking very grim since no confirmed sightings have been reported in 14 years 😦

The sad state of handfish is ironic as, not unlike other endangered or extinct species, they used to be very common. So common in fact, that less than 50 years ago, the local university used them as a model animal for dissections in zoology classes! Early Tasmanian settlers and convicts even considered eating them because they were found everywhere and were easy to collect, but decided against it because they were too small (less than 10cm).

So what went so wrong that we now fear they might go extinct? The main reason for their issues is habitat destruction and degradation. The combined effects of destructive fishing pressures, coastal development, increased pollution and silt runoff means that much of the places they used to thrive are no longer suitable. To add insult to injury, the waters home to handfish have been invaded by the Northern Pacific Seastar (Asterias amurensis). There are now millions of them in prime handfish habitat, and they love to eat handfish eggs and the stalked ascidians the Spotted handfish lay their eggs on. Without a proper place to attach their eggs, the handfish can’t reproduce anymore, with a crashing population as a result.

^{The critically endangered Spotted Handfish (Brachionichthys hirsutus). Photo credit: Rick Stuart-Smith}

Luckily for the handfish, a dedicated group of people are trying their very best to turn its fortunes around. The Handfish Conservation Project is a team of researchers and conservationists that is working hard to save these amazing species. The project has mapped out recovery plans, does research on handfish to better understand how we can help them, and has a citizen science portal to report handfish sightings. In a very cool recent project, science and art were combined successfully to make ceramic egg habitats that are unpalatable for the invasive seastars, but acceptable for handfish to lay eggs on.

If, like me, you want to help conserve these fantastic critters, there’s a few things you can do. If you see Red or Ziebell’s handfish, please report it here, ideally accompanied by pictures. If you can and want to, you can donate to the project here. If you are really keen, you can even name an endangered handfish! For more general info on handfish conservation, the Handfish Conservation Project website is a good place to start.

^{The Red Handfish (Thymichthys politus) has good reasons to look grumpy. Photo credit: Tyson Bessell}

TEDx talk: Small critters and ocean health

November 15, 2019November 15, 2019 / Maarten De Brauwer / 1 Comment

Last September I had the pleasure of doing a TEDx talk in Stuttgart. The video is online now so you can check it out on TED or just watch below. The talk combines aspects of my research on small critters, biofluorescence and environmental DNA. I hope you enjoy watching it as I enjoyed doing the talk 🙂

Wondering about mimics?

April 27, 2019April 27, 2019 / Maarten De Brauwer / Leave a comment

I have been meaning to write a blog about the Mimic octopus (Thaumoctopus mimicus) and Wunderpus (Wunderpus photogenicus) for ages, but inspiration has eluded me until I was revisiting some of my earlier research on charismatic muck dive species. Both the mimic octopus and the wunderpus are very popular with critter enthusiasts, but we know surprisingly little about them. Time to change that or at the very least tell you some of the things we know about them!

A wunderpus (Wunderpus photogenicus) checks out my camera

If you’re not a diver or you have never heard of them, the Mimic and the Wunderpus are very (very!) funky species of octopus. They have a wide range of interesting behaviour, they look amazing, and both are found on sandy habitats in the tropics. What they also have in common is that both were only recognised as new species fairly recently (2005 and 2006).

Just by reading their scientific names you could imagine these are not your average cephalopod. The wunderpus’ species name “Wunderpus photogenicus” says it all and is probably also one of the easiest scientific names to remember (except maybe for the brilliantly named “Boops boops“). “Thaumoctopus mimicus” tells you that this particular species is good at mimicry, even for octopus standards.

Mimic octopus (Thaumoctopus mimicus) foraging on the sand

Both species live on soft sediment (mostly sand) habitats and they have evolved to be perfectly adapted to this lifestyle. They live in holes in the sand, are small, have longer arms than your average octopus, and their colours are quite drab. There are a few subtle physical and behavioural differences between the two though.

Wunderpus partially in its hidey-hole

One of the things I noticed is that their hunting strategies vary slightly. Wunderpus have more extensive “webbing” between their arms than mimics and they use this webbing when hunting. Crabs are a favourite prey of wunderpus and they catch them by spreading their mantle (the “web” between their arms) over rocks, holes, or other objects like a big parachute. They then use the tips of their arms to poke the crabs out of their holes, after which they run into the parachute-web and are easily collected with one of the other arms.

Mimic octopus seem to forage more actively and (in my experience) use the parachute-technique less often. Instead they poke their long arms into holes in the sand, scaring out any critter that’s in there and then grabbing it directly. This means that mimics spend even more time moving over the sand than wunderpus do, which might be why they evolved some very particular behaviour.

Trying to mimic?

Whenever you search for information about the mimic octopus, one of the first things to come up is that they mimic all kinds of other animals. Unlike other octopuses, it does not just mimic colour, but also the behaviour of up to 6 (or 8 or 12 depending on who you ask). The question is, does a mimic really mimic? Their mimicry is supposed to deter or fool predators or prey, but I wonder if this is really the case, or whether we are over-interpreting things from our human perspective.

Many of the behaviours that have been called mimicry could also be explained by simple logic or physics. Take for instance the idea that they mimic toxic flounders/soles while swimming. Yes, they do look very similar when they swim, but it is also a fast and energy-efficient way to swim over any flat area. Which is undoubtedly why this type of swimming is used by most octopus species living in the sand. Another example is the lionfish-mimic, which could also be explained as a way to look as big as possible when threatened. It’s a very common tactic used throughout the animal kingdom, and if you happen to be an octopus with long arms, you’ll look like a spiky lionfish when spreading them out. Other behaviours can similarly be explained, but I wouldn’t want to bore you with long lists right now.

Does this mean they do not mimic or that I am just a mopey cynical bastard who refuses to be amazed by a fantastic animal? Of course not! I love mimics and they show some of the most extraordinary behaviour in the ocean. It just means that I want to learn more about them to find out what causes it.

Close up of a mimic octopus

To study them properly, you first need to be able to tell the wunderpus and mimic octopus apart though! These critters look very similar (stripey), so it’s easy to get confused. Here is what to look for:

Arm patterns I: The black/white patterns on the arms of Wunderpus are very sharply defined, compared to more blurry with the mimic. Imagine the patterns on the wunderpus were drawn by a German painter using a pen and ruler, and the ones of the mimic by me with some crayons.
Arm patterns II: Mimic octopus have a continuous white outline along the border of each arm. The wunderpus does not have this, instead the band-pattern continues across the border.
Head: Mimics have a “U-“-shape on the back of their head, where wunderpus have a white patch.
Colour: Wunderpus usually have more of a red/brown colour shade to them than mimics, which are almost always black and white. Careful though, they can both change colour so this is not the best way of telling them apart.
Behaviour: The hunting behaviour I described earlier is a hint, though not always consistent. From my experience, wunderpus live in areas where the sand is more coarse (gravelly) than mimic octopus, which could also explain why they have slightly different hunting methods.

Finally, because you made it this far, here is a video I took of mating mimic octopus in Indonesia:

Leafy seadragons: Australia’s favourite fish

November 20, 2018November 20, 2018 / Maarten De Brauwer / 4 Comments

In a recent poll organised by the Australian Society for Fish Biology and Lateral Magazine, the Leafy Seadragon (Phycodurus eques) was voted as Australia’s favourite fish. This exquisite critter definitely deserves its place at the top, to celebrate it amazingness I wrote a blog about it. This blog appeared originally as an article in Lateral Magazine, you can find the original version here.

According to the popular stereotype, marine biologists spend their careers diving on colourful coral reefs, cuddling dolphins, and wrestling sharks. Unfortunately, the truth is a lot more mundane; we are more likely to spend our days diving into data analyses, cuddling too many cups of coffee, and wrestling grant proposals.

But sometimes we get lucky enough to work with animals that exceed the wildest stereotypes. Studying marine life is always exciting, but some animals are so unique they just stop you in your tracks; they make you thank your lucky stars for not listening to your mother when she said ‘marine biologist’ was not a real job.

Two leafy seadragons. Photo credit: David Harasti

For me, the ultimate awe-inspiring fish is the leafy seadragon (Phycodurus eques). “Leafies” only occur in temperate waters off southern Australia, and they are, to say the very least, unique animals — the kind that makes you wonder whether evolution had a stroke of brilliance or just a stroke. Seadragons belong to the Syngnathidae family, which also includes seahorses and pipefishes. Even in a family that is known for their oddly-shaped members, leafies stand out big-time.

These beautiful fish have the head of a seahorse and the body of a seaweed, with flamboyant leaf-like protrusions that wouldn’t look out of place at the Carnival in Rio de Janeiro. Leafy seadragons defy the idea of what a fish should look like.

Maybe that is why they are so popular with fish enthusiasts all over the world. Scuba divers fly halfway across the globe to dive in the cold waters off southern Australia, hoping to catch a glimpse of them. In the few public aquaria that display them, including Melbourne Aquarium, leafies are one of the absolute crowd-pleasers. For fish-lovers, this Australian endemic fish is at least as iconic as kangaroos or koalas.

Leafy seadragon. Photo credit: Tony Brown

Despite their popularity, we know surprisingly little about leafy seadragons. Adult leafies are one of the largest members of the Syngnathidae family, with adults measuring up to 35cm. Like seahorses, male seadragons carry their mating partner’s fertilised eggs; unlike seahorses, they do not have a pouch. Instead, females lay their eggs on the underside of the male’s tail, where they remain until hatching.

Leafy seadragons depend on kelp and seagrass beds as their habitat, where they blend in supremely well to avoid predators. Unfortunately, these habitats are in decline all over the world, including in Australia, caused by coastal development and potentially climate change. As a result, seadragon population numbers are decreasing, although the species is currently not considered to be endangered.

Admiring a Weedy seadragon, a close cousin of the Leafy seadragon. Photo credit: Greg Lecoeur

One would assume that the decreasing population numbers of a unique Australian emblem would inspire multitudes of researchers to study it. Strangely, this is not the case. A search of the scientific literature suggests that nobody has studied them in the wild for almost a decade. This lack of research on evolutionary distinct marine critters is unfortunately not unique to seadragons. It extends to many other species that do not fit in the ‘food’, ‘danger’, or ‘Pixar-famous’ categories in which landlubbers like to divide marine life. If so little attention is paid to the struggles of Australia’s most recognisable and charismatic fish, then what hope do other species have?

Time will tell what the future holds for the leafy seadragon. I, for one, am doing what I can to ensure generations after ours will continue to have their minds boggled by this incredible animal. If you care about seadragons, one way to help is to join citizen science projects such as iNaturalist or Seagrass Spotter. These projects collect observations from divers and snorkellers, directly helping scientists better understand and protect these animals and their habitats.

A short note about this blog: Two weeks after the poll I was awarded a research grant by the Sea World Research and Rescue Foundation to study the seadragons using eDNA. Hopefully the results that will come out of this research will help to better understand and protect these beautiful fishes.