Sea dragons – why it's worth flying 16,000 km to South Australia

Corona issues aside, people fly to South Australia for all sorts of reasons: many just want to see some boulders in the sea between Melbourne and Adelaide called "The 12 Apostles", others go to see motorbike races on Phillip Island near Melbourne, and we aquarium nuts fly halfway around the world to observe some of the most bizarre fish around: the seadragons!

Anyone who has seen these fish for the first time in photos, film or an aquarium can’t help but be amazed and thrilled. Seahorses barely fifty centimetres long, colourful or with algae-like appendages. I don't think any of us would travel to South Australia without wanting to see these very special fish in the sea.

There are two species of seadragons: the large seadragon Phycodurus eques, also called leafy seadragon or leafy by the Australians, and the small seadragon Phyllopteryx taeniolatus, that the Australians call weedy seadragon (with its alga-like appearance).

Neither species lives in the warm regions of Australia, they’re only to be found in the cold waters around the south coast of the continent. The range limit for both species extends up the west coast to 200 km north of Perth, completely along the south coast including Tasmania, and then it ends for the leafy seadragons at Melbourne, while the weedy seadragons still appear along the east coast up to the Sydney area.

My first encounter with the weedy seadragons

My first encounter with the weedy seadragons, which at 45 cm are not actually small at all, took place near Sydney. During the day I was busy at work, so I only had the night for diving. In the evening, I took a taxi from the hotel to the dive shop to pick up the compressed air cylinder I had ordered by phone and then to the next beach called Shelley Beach, a little north of Sydney. The taxi dropped me off at the dark beach with all my stuff and off it went. For the somewhat fresh, 19°C water, I needed a 6 mm suit. The sunshades on the deserted, nocturnal beach looked a bit spooky, but the anticipation of the chance to find sea dragons outweighed everything else. I entered the cold water, briefly set the compass to the coast and off I went. A beach area like this is already pretty bleak underwater during the day, but at night it's even bleaker - if that's even possible. The first creature in the sandy desert was a Port Jackson shark, which feeds exclusively on crustaceans and mussels. They also seem to be extremely affectionate, as this one stayed with me for the entire dive! I was terrified every time it swam under my arm and within range of my diving goggles. The sandy bottom seemed endless, but there are interesting fish living there. You just have to find them! After another 20 minutes I found a ray, then another and another. The really great thing about cold ocean regions is that we don't know most of the species. As marine aquarists, we are kind of familiar with most tropical species, but the cold-water species? When I came across a motorbike wreck, I’d had enough. No seadragons, no diversity of fauna, just the rays and my faithful companion. I briefly dived to the surface to get my bearings. I wanted to get to the eastern shore of the bay, not to the open Pacific. There would be rocks and therefore more life. And indeed: the rocks were full of life and it got really exciting. First I was able to observe a large catfish in speckled yellow. As far as I know, there are only two species in the sea: Plotosus lineatus and P. canius. But neither of them is speckled yellow as an adult. Definitely a new discovery, because what fool goes looking for fish at night in this white shark region?

And it continued to be exciting: mouth-brooding cardinalfish with full mouths swam between the rocks, but were too careless and were immediately devoured by the well-camouflaged carpet shark. The normally harmless carpet sharks are responsible for the most diving accidents. These sharks lie on the ground and divers accidentally grab them by the tail and then receive an unexpected bite on the hand. Carpet sharks are so agile that they can reach their tail fin and thus the diver's hand with their mouth!

Goatfish were lying around sleeping and it's always fascinating to see what night dress our fish don! Some species look completely different at night than during the day. No idea why, because there is no light to show off the night colouration to advantage. When there is a full moon, it is relatively light down to a depth of five metres underwater, but even below that depth they wear their pyjamas. No matter - I'm here to look for seadragons. Starfish are crawling around me and the animals are so beautifully coloured that I immediately wonder what a cooling unit for my aquarium would cost. What a blaze of colour!!!

And then finally: a seadragon! The guy is a good 40 cm long and doesn't like my lamp at all. Luckily, he can't swim fast with his little flippers. I would have loved to just turn him over to get a portrait of him. But you don't do that, even if there’s no one watching.

I watched the seadragon until my bottle was absolutely empty. What an encounter! With an empty cylinder, I snorkelled back to the beach and pondered how I would find a taxi back to the hotel in this lonely region...

In search of the leafy seadragon

As there is only the weedy seadragon near Sydney, I travelled further south to Adelaide. A marine biologist friend of mine, Ben Brayford, told me that there was a good chance of seeing the leafy seadragon there. He took me south of Adelaide, towards Kangaroo Island, to a pier that was beyond ugly. With shining eyes, he told me about the leafy seadragons he had already seen here. I had pictured a beautiful wild beach, but not a half-ruined concrete pier in the middle of nowhere. But Ben was so excited and there had to be a reason. The water was quite a bit colder, so I was surprised that our third man didn't put on a diving suit. His short explanation: "It's summer and only wimps wear suits." Okay, I'm one of those wimps, but I was immediately surprised when the two of them strapped some kind of electrical device to their legs. Since several attacks by great white sharks occurred on the south coast of Australia, the government has made electrical shark repellent devices mandatory. They are supposed to be able to repel sharks through electric fields. So that’s the sum of it: my two companions were well equipped and I wasn’t. The water was not only cold, it wasn’t really clear either. Huge algae colonies prevailed, broken only in places by rock formations. A first glance at the Ecklonia algae made it clear why the leafy seadragon were perfectly camouflaged by their body shapes. Their body appendages were a perfect imitation of this type of algae. Since this algae only exists in cold water, they would be without protection in more northern and thus warmer water. If you google the name Ecklonia, you will be offered all kinds of miracle cures made from this alga.

At a larger rock formation I discovered the relatively rare Bleeker's blue devil fish (Paraplesiops bleekeri). I only knew the animal from photos and it was fantastic to observe the real thing for a while. These fish, which grow up to 40 cm, are found exclusively in south-eastern Australia. Why they are restricted to this region is unclear. They are actually crepuscular and hide in caves and crevices during the day. My specimen didn’t seem to know this and was perfectly happy out at midday. I searched intensively for a second specimen, because they do very intensive brood care. I had lost sight of my two companions in the murky soup some time ago and I hoped that the great white sharks were out somewhere else today. I have to admit that I didn't feel that good about being in murky water with the threat of an encounter with a white shark. In the surrounding algae I finally found my first leafy seadragon! Its real size of 35 cm surprised me a bit. The yellowish colour is typical for animals that live in shallower regions. At greater depths they show darker colours. As with all seahorse species, the male is responsible for brood care. However, the males carry up to 300 eggs OUTSIDE their bodies in their tail region instead of in a brood pouch. Because they are bred here in Australia the animals are permitted to be exported to show aquariums all over the world. However, no aquarium can ever recreate the fish's habitat with true Ecklonia algae. Large seaweed cannot be maintained permanently in aquariums with artificial seawater. The Biological Institute Helgoland did experiments with cold-water algae and were only able to successfully cultivate algae in aquariums over long periods of time when they added real North Sea water to the tanks. No matter what trace elements they added artificially - the algae always perished. The large show aquariums in Tokyo and Monterey also experienced this problem and have therefore built large pumps with pre-filters in the sea, which pump the water into the metre-high aquariums. This is the only way visitors can marvel at real kelp (brown algae up to 30 m high). In the 7 m high kelp aquarium of the Haus des Meeres in Vienna, (relatively authentic-looking) plastic kelp is used because of this problem.

Seadragons in aquariums?

Seeing the leafy seadragon in "ITS" Ecklonia algae made me think of the specimens that eke out a living with plastic algae in the Sydney Aquarium. Sydney must be in a position to pump real seawater into the aquariums too. It's probably too costly...

Apart from the algae, caring for seadragons in aquariums from 800 litres is not difficult. They fairly quickly get used to eating small mysis, large artemia and other food, as long as it moves. However, they eat as slowly as seahorses and should therefore not be socialised with other fish. By the time seadragons and other seahorse-related fish realise that food is available, the other fish have already eaten it. The trickiest part when caring for seadragons definitely involves the water temperature. It should never rise above 20 °C on a permanent basis, and here in Germany this can only be achieved with large and therefore expensive cooling units.

At JBL, just like the Biological Institute Helgoland (BAH), we also once undertook experiments on algae cultivation and were actually able to maintain some tropical brown algae over a long period of time with our TRACE MARIN trace element range. One finding was that protein skimmers skim off large amounts of trace elements before they are used by the invertebrates and algae. So an analysis had to be made of which trace elements are skimmed off and in what quantities, and the concentrations in the product was adjusted precisely to this. But with cold water species it seems to be a whole lot more complicated!

Back to the encounter with our giant seahorse: Fortunately, it is not difficult to take photos of the leafy seadragon. It is, like its colleague the weedy seadragon, quite sluggish and relies on its camouflage. Even with macro shots of its imposing head, it didn't realise that its cover had been blown. I wish I saw such relaxed fish more often. Wrassen with their bouncing swimming style may drive an underwater photographer crazy, but seadragons? They are absolute top models!

© 11.09.2022

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Heiko Blessin
Heiko Blessin
Dipl.-Biologe

Tauchen, Fotografie, Aquaristik, Haie, Motorrad

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