Do Fish Fart?

Following on from our Facebook post about fish who sing (yes, really…see the news clipping below!), we have pondering if they make any other human style noises. So here we are…debating whether fish fart or not! Too much spare time on our hands? Maybe!

Loving the reference to childhood favourite 'Operation'. Brilliant!
Loving the reference to childhood favourite ‘Operation’. Brilliant!

Believe it or not, whether fish suffer flatulence is an ongoing debate among ichthyologists (people who study fish). So…. do fish fart? As with many such hotly debated (?!?!) topics the answer depends on the definition of farting. If you consider farting to be the by-product of digestion – in other words gases expelled from the rear end – then most fish don’t fart. However there are two exceptions, the shark and the herring. It is reported that the sand tiger shark purposefully gulps air into its stomach at the surface then farts it out at the other end so it sinks to its desired depth!

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Biologists have also linked a mysterious underwater farting sound to the bubbles coming out of a herrings’ rear end. It apparently sounds like a high-pitched raspberry, and biologists now believe it is how the herring communicate to each other in order to keep their shoal together at night and alert other fish of their presence! Lets hope that’s a trend that remains firmly in the fishy world and doesn’t start to catch on above land too!

Bubbles

 

This phenomenon has been named Fast Repetitive Tick and once even sent the Swedish navy scrambling for answers. Top on the hit list of probable causes was a Russian submarine, so discovering it was only herring and not in fact an army of spies came as a relief! The herring are not entirely alone though. Some other marine fish also make quite distinctive gassy sounds. For instance cod/groupers make their swim bladder vibrate to produce a kind of drumming sound, whilst some other fish make noises by belching. But so far it’s only some herring species that seem to use the ‘art of the fart’ to communicate. So while in polite society flatulence is considered a social faux pas, for a herring it is an important social tool!


 Grouper

 So, there you go! Happy bubbles folks….the kind that comes out of your regulator, obviously!

The Artificial Reefs of Koh Tao

Artificial Reefs are becoming more and more popular as divers worldwide become more environmentally aware. Artificial dive sites provide homes/shelter/safety for a variety of marine life, and also alleviate the pressure from regular dive sites, which is especially important in heavily dived areas. Koh Tao has been developing and promoting artificial dive sites for a number of years, and Master Divers has been actively involved in assisting with the construction and maintenance of some of these too. Our favourites on Koh Tao are:

Junkyard

As the name suggests, Junkyard is an artificial reef made out of, well… junk! Not your regular sort of everyday trash, but lots of larger, bulkier items that would otherwise be difficult/expensive/environmentally unsound just to throw in landfill and forget about! There’s a pickup truck, a Sydney Harbour Bridge, a mini gym, a windmill, a pyramid, several cage structures on which transplanted coral grows, long metal archway tunnels – great for practicing swim-through buoyancy techniques, and even a sculpture made out of old toilets – which as you can imagine has been the backdrop to many an ingenious photo moment!

A Diver Swims Beneath the 'Coconut Monkey Tree'
A Diver Swims Beneath the ‘Coconut Monkey Tree’

 

In and among all of these man-made monuments you’ll often find juvenile Longfin Bat Fish, Puffer Fish and Box Fish of pretty much every shape, size and species, a few varieties of File Fish (most of which cannot be found at any other dive site around the island), Saddleback Anemone Fish, and often some Crabs & Shrimp too. Night dives to Junkyard are also pretty impressive. Giant Hermit Crabs wander to and fro and Blue Spotted Sting Rays also come out to hunt along the sandy bottom. If you’re lucky, you may even spot some Pleurobrach, a type of marine slug. Nothing unusual there you may think, especially if you’re well versed in your Nudibranchs. Pleorobranchs, however, are much bigger – normally dwarfing their Nudibranch counterparts by a ratio of over 100-1!

Juvenile Batfish
Juvenile Bat Fish

 

Bio Rock

BioRock was where it all started in terms of artificial reefs on Koh Tao. A collaboration between marine biology students from mainland universities, a number of dives schools worked together to sink Koh Tao’s first official artificial. Bio Rock – or Hin Fai, as it is also known – is a large dome structure with smaller satellite dome structures and boulders surrounding it. The domes are used as a base structure on which to attach transplanted corals. The special and unique feature however, is that the dive site is fed by an electrical current from the land in the form of cables, which encourage and hasten coral growth – the idea being that corals grown here can be transplanted to other dive sites on the island where the health of the reef has declined.

In his 2012 paper focusing on Coral Reef Rehabilitation, Gerianne Terlouw noted “We find that corals on the Biorock structure grow up to 80% faster than corals in other reef areas when conditions are optimal.”

 

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Corals Growing on the Dome Structures

 

HTMS Sattakut

As artificial reefs go, shipwrecks are one of the most popular, and we are lucky to have the HTMS Sattakut on our doorstep. This 49metre long naval war ship sits in 20-30metre depth region, so is perfect for fun divers (if qualified to dive below 18metres of course!), wreck adventure dives and wreck and deep specialties alike. Sitting upright on her flat bottom with impressive cannon style guns at the front and rear, a circular conning tower, and numerous port holes to peer through, she’s an easy wreck to explore. Over the years we’ve documented this wreck in our blog a few times. You can read more about her and research more links, from our post on the sinking of the Sattikut here.

Peeking Through a Porthole
Peeking Through a Porthole

 

Around the wreck you’ll likely spot large Groupers, Andaman Sweetlips, and schools of Rabbit Fish as well as Big Eye and sometimes even Giant Trevally. Schools of juvenile fish such as Yellow Tail Barracuda often inhabit some of the rooms inside the wreck, and use their artificial home as protection against larger predators. In crevices hiding under the wreck you can often see Jenkins Whip Rays too.

Giant Grouper

 

Buoyancy World

Not quite Disney World, but for inquisitive divers who enjoy seeing something a bit different on their dives, Buoyancy World definitely provides a fun factor. Located next to Twins, and easily navigable within a dive at Twins itself, Buoyancy World comprises of a number of structures designed to aid with buoyancy training. Because of this it is regularly visited on PADI Advanced Open Water training dives and PADI Peak Performance Buoyancy Specialty courses. Another collaboration between a few Koh Tao dive centres, it has hoops and squares, a mini maze, concrete rings and even an octopus to help hone your buoyancy, trim and swim-through techniques. It also has some additional structures such as a shark, turtle, some phone box-like structures and a host of concrete blocks that attract marine life and curious divers alike.

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Buoyancy_World_Koh Tao_Ayesha_Cantrell_001

 

This list is by no means extensive, and several other dive sites now have artificial sections too. You’ll find an extensive concrete block site at Hin Ngam, ‘Utopia’ structures at Tao Tong, reef balls (and even a couple of motorbikes) at Tanote Bay, and many more besides. Interested in diving some artificial sites? Let us know and we’ll be only too happy to schedule some for you!

Jellyfish: Totally Under-Rated Beauties

When people enthusiastically talk about their favorite underwater animal encounters, most divers will mention whale sharks, manta rays, turtles etc… and while these are animals that certainly get your heart racing (they definitely do for me!), there is something about the majestic jellyfish that makes my heart sing with every graceful movement.

Much like sharks, Jellyfish tend to bring out feelings of fear and apprehension amongst scuba divers, snorkelers and swimmers alike…Understandably, since their tentacles are widely known to cause a world of pain if touched – even I have experienced the indescribable agony of being stung by the infamous Box Jellyfish. But rather than associating all Jellyfish with fear, that experience was a sobering reminder that all creations of nature are to be respected and appreciated. I have come across many different types of Jellyfish in nearly 3 years of living on Koh Tao and each encounter has had me researching more and more information about them. Here are some of my photos and a few little fun facts about these incredible creatures:

 

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They are food for a number of animals that live in the ocean such as turtles, big fish, small fish and sometimes even birds!

 

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Jellyfish provide a habitat for many types of juvenile fish. You will often find them living inside the bell or flitting around between the stinging tentacles. Some animals such as tiny crabs and brittle starfish can be found attached to the bell of the Jellyfish… they like to hitch a free ride to avoid moving around on their own.

 

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Fossils of Jellyfish are very rare because they lack a skeleton – however there has been evidence suggesting that their existence predates dinosaurs by 400 million years! Whoa…

 

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Jellyfish are typically very difficult to identify – there are around 1000-1500 known species in our oceans worldwide. This one is in the Chrysaora family, but which sub-species is it? Seriously, no idea 😛

 

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Jellyfish are invertebrates. They lack a backbone, heart, blood, brain, and gills and are in fact made up of over 95% water.

 

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Not all Jellyfish have the ability to sting… but some species possess millions of small stinging cells in their tentacles called Nematocysts. These cells are used to capture food by injecting toxin into the prey. Keep in mind that even if a Jellyfish has died or if the tentacles are severed, the Nematocysts stinging cells remain active for some time and therefore can still deliver a sting!

 

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It is actually relatively easy to protect yourself from the sting of a jellyfish… simply wear exposure protection such as a wetsuit when swimming/snorkelling/free-diving/scuba-diving in the ocean. Always look around for jellyfish while in the sea and keep a healthy respective distance when encountering one. If you find that you have been stung by one, start by removing any tentacles still stuck to you using gloves and a tweezer as soon as possible, irrigate the area with vinegar and only rinse with SEA WATER.

 

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Jellies are carnivorous animals and hunt their prey by using their tentacles as a drift net. They typically feed on plankton, crustaceans, fish eggs, small fish and other jellyfish. They also eat and poop using the *same* hole in the middle of the bell (ewwwww!).

 

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Did you know that a group of Jellyfish is called a “Swarm” or a “Smack”?

 

So there you go… a few fun and interesting facts about Jellyfish! Needless to say, I love and adore all jellyfish and would never hesitate at the chance at being in the water with them whether snorkelling or diving. They are totally fascinating and gorgeous animals with mesmerizing movements that actually has a calming effect… just please remember that all marine life should be respected – and maybe a small healthy dose of fear doesn’t hurt 🙂

 

Look But Don’t Touch!

There are at least 1200 species of venomous creatures in the oceans around the world, and while we are incredibly fortunate here on Koh Tao that we are not home to many, we do have some inhabitants that can pack a punch if not treated with the respect they deserve! Read on to find out more, but do bear in mind that all of the marine life we will discuss here are very passive, and will not cause you any harm if you interact sensibly with them, and abide by the most important golden rule of diving – look but don’t touch!

 

The Scorpion Fish (Family Scorpaenidae)

This family includes not just Scorpion Fish, but also Stone Fish, the Indian Walkman and the Lion fish. All of these fish are masters of camouflage, and have spines that can inject toxins into any predators that get too close. Whilst Stone Fish are not native to Koh Tao, those with a keen eye may find Scorpion Fish at most dive sites. Lion Fish are seldom seen here, but there are a few – especially when exploring out in the sand at Pottery or in the channel at Japanese Gardens. And whilst difficult to spot, Indian Ocean Walkman’s are most often found on night dives, most commonly at White Rock.

 

The Bearded Scorpionfish gets its name from the gills that hang below its mouth like a beard
The Bearded Scorpionfish gets its name from the gills that hang below its mouth like a beard

 

Indian Ocean Walkman
Indian Ocean Walkman

 

The Lion Fish with its impressive display of fins
The Lion Fish with its impressive display of fins

 

The Puffer fishes (Family Tetraodontidae)

These funny looking fish has a highly elastic stomach and has the ability to take in huge amounts of water or air if necessary, to blow itself up into a huge ball several times their size, protecting itself against predators. However, if a predator manages to grab a puffer before it inflates it will come off rather badly. Most puffer fish contains tetrodotoxin, a substance 1,200 times more toxic than cyanide, that makes them taste foul and often is lethal to other fish.

Porcupine Pufferfish
Porcupine Pufferfish
Starry Pufferfish
Starry Pufferfish

 

The Banded Sea Snake (Laticauda Colubrine)

These can grow up to 128cm long with anything from 20-65 bands.  The sea snake is quite a docile creature and not at all aggressive unless provoked.

Banded Sea Snake
Banded Sea Snake

 

The Crown of Thorns (Acanthaster Planci)

This majestic looking and unusually large starfish which can grow up to 1m in diameter. It has up to 21 arms, with the entire upper surface of its body covered in long venomous spines that can break off and become embedded any predator that gets too close. They are voracious predators that release the contents of their stomach on to the coral. Digestive juices then liquefy the coral ready for consumption. A single individual can wipe out large areas in this way and has scientists concerned as it is playing a major role in the destruction of the coral reefs in Australia.

Crown of Thorns Starfish
Crown of Thorns Starfish

 

Jelly Fish

We do get a variety of jellyfish here on Koh Tao, although the most common time to see one is when you’re sitting at your safety stop depth above one of the dive sites.  Jellyfish have no method of propulsion of their own for direction, so are ultimately at the mercy of the ocean currents and waves for where they end up.  All jellyfish have stinging tentacles, for which the treatment for contact is vinegar (or pee!) over them as soon as possible. This prevents any un-discharged stinging cells on the tentacles from firing even more venom.

Jellyfish in the Depths
Jellyfish in the Depths
A crab hitches a ride!
A crab hitches a ride!

 

For more information about the species commonly found around Koh Tao, feel free to check out our marine life page. You could also ask one of our dive leaders, all of whom are full on fun fishy facts about creatures found in our tropical waters! And whilst diving always remember the golden rule…..look don’t touch!

A Day in the Life Of….A Titan Trigger Fish!

Ever wondered how a Titan Trigger Fish spends their day? We think it goes pretty much like this…

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06:00 – Wakey wakey, rise and shine! So what am I going to do today, I wonder!

06:46– Been cruising around, chomped on some coral and eaten a few sea urchins. I must try to pick ones with shorter spines. I spent far too much time biting them down to a manageable size.

08.05 – Come on, come on, where are those weird fish that blow air bubbles?? I do like to chase them every once in a while!! Hang on, ding dong, she’s a bit of a hottie!! Oh no, she’s a Yellow Margin Triggerfish. Must remember to stick to my own kind….

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08:20 – Did I just hear something? Was that splashing I can here? Oh look those weird fish are flapping around on the surface – that always seems to happen when they first appear.

08:30 – Hey, you, Mr Blue Spotted Sting Ray! This is MY territory! Find your own resting place! I do like this little overhang….

08:40 – Hmm, that was an effective little charge – soon told that Angelfish who’s the boss around here. Who does he think he is with all his fancy colours and blue rings….

08.50 – Oh good! My favourite type of coral….Chomp, chomp, chomp…

09.05 – Oh, it’s all quiet again. Now I think it’s time to build a nest…..I’m just in the mood for a bit of head-banging. Where will be a good place…..?

09:45 – I found an excellent location, a little bit away from the coral, and just underneath that line that those bubble-blowing creatures seem to spend so much time hanging around. I wonder what they find so interesting about it – up and down, up and down. Sometimes they hardly seem to leave it alone, and then they are back again!

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11:20 – My new nest seems just about the right depth. Slightly deeper might be better, but this will do for now; I can always extend or refurbish next season…

12:50 – Oh, Splashing time again. With all that head-banging and nest building done, I think it’s time for some fun…

12:55 – Charge! Look at that! Brilliant! All the bubble creatures have scattered in all directions – it looks just like a firework going off! Oh, oh, they are re-grouping…..Let’s have another go! Weee…..and again! Oh go on, just one more time…..

14:20 – No point putting it off any longer, I simply must do some housework. Now, I want to move this piece of rock over here… that was a bit heavier than I thought – good job I have a strong jaw. And I think that piece of coral will look marvellous right next to the rock….Hmm, let’s just move it another centimetre…Perfect! My interior design skills really are coming on a treat.

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15.05 – Yum! That swimming crab was a tasty little morsel. And I gave that floating bubble-making fish thing a bit of a fright too. Haha! You thought I was coming for you, didn’t you?

15.20 – Oh what now!!? How did that bubble fish creep up on me like that? Invade my personal space! I’ll show you – this time here will be no mercy – hahaha! Trigger up, hold it, hold it…..CHARGE!

15.25 – I won, I won! And I got a prize – I got one of those fins!!  Woohoo!

Grumpy Triggerfish

 

15.30 – OK, now what am I going to do with the fin? It really is the wrong colour – how am I going to fit this into my colour scheme at home? Oh well, I think I’ll leave it….It’s got a few holes in it now anyway.

15:40 – Time for a bit of a rest I think. I’ll just swim out into the sand and sit down for a bit….

19.00 – Steady on, what was that?! Where did that bright light come from? Do you realise what the time is?! It’s past my bedtime! Oh, and another one, and another one….When will it end!!

19.20 – Hmph, I don’t like those bubble fish at night time, I can’t see them properly to get a good charge at them, and they keep shining that big bright light in my face whenever I try.

19.30 – Time to admit defeat and slope off to that nice crevice I spotted earlier today, hope that annoying parrot fish hasn’t taken up residency there already.

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19.40 – Still a few lights around but if I hide in here they will go away. I’ll make those bubble fish pay for blinding me with their silly lights. Just wait ‘til tomorrow when I can see them better. Mwah hah hah haaa!

20:12 – At last, the boat engine noise has disappeared. Good night my fellow fishy friends! Zzzzzzzzz…….

 

Fascinating Fish Facts

There are over 25,000 known fish species, and an estimated 15,000 still undiscovered. Although we are yet to discover all the fish on our planet, the ones we know of are truly amazing! Here are 12 fascinating and slightly surprising facts about some of our Oceans most interesting fish:

1. The Giant Squid’s brain wraps tightly around its throat, and therefore risks brain damage if it eats anything too big. Now that would be a final supper to die for!

GiantSquid

2. A shoal of fish refers to a collection of fish who swim together in a similar direction, but act independently. Whereas a school refers to a group of fish who move and manoeuvre in a tight synchronised formation for the purpose of hunting, protection, or mating.

3. Fish in the centre of a school control the passive movement by reacting to water pressure changes that are detected by sensitive hairs in their lateral line.

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4. Fish can suffer insomnia and have an innate inability to sleep.

5. In a New York University experiment, a robotic fish was accepted into a community of other fish and became the most dominant fish and leader.

6. A collection of Jellyfish is known as a ‘Smack’ of Jellyfish

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7. Certain species of fish will change sex throughout their lives. Clown fish all start out as male, but the most dominant male will change sex if the groups female dies. Parrot fish have the sex organs of both male and female, and can therefore change sex throughout life.

8. Sharks are the only fish with eyelids which serve to protect the eyes when attacking prey.

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9. Fish can actually drown in water. They respire using the oxygen in the water, and therefore will suffocate in oxygen-starved waters.

10. Herring communicate through farts

11. Fish have taste buds all over their bodies. Catfish in particular have 27,000 taste buds, whereas humans have only 9,000.

Catfish

12. When Anglerfish mate, the much smaller males attach onto the body of the female and meld their for the rest of their lives, sharing gametes and bodies forever.

Species of the Month: Crown of Thorns

 

The Crown of Thorns is a beautiful multiarmed sea star that holds a notorious reputation around Indo-Pacific waters for being dangerous to shallow coral reefs. They are a corallivores animal, meaning they prey on a primary diet of coral polyps, causing serious damage to unprotected coral. Adults can grow to a diameter of around 12 inches, the majority of which is covered by their large circular bodies of which their short arms protrude from. Their surface is covered by long sharp spines that carry a harmful venom. These spines have no injecting mechanism, however the venom can be carried by tissues if punctured by the spines causing a stinging pain, inflammation, and persistent bleeding as the toxins prevent blood clotting; so watch out! Fortunately Crown of Thorns are relatively easy to spot while diving due to their size and exotic colours which are often displayed as warning colours for would-be predators.

Crown of Thorns

As mentioned, the Crown of Thorns are a danger to coral reefs due to their predatory habits. To begin feeding, first the sea star must station itself on a coral surface and excretes its stomach out underneath its body to spread to the full reach of its diameter. It then secretes a powerful enzyme that begins to break down the coral exoskeleton in order to filter and absorb the nutrients from the liquefied coral tissue. This does not kill the coral, but leaves the bare skeleton very vulnerable to infestation by several algae which prevents rejuvenation.

This is a natural part of the ecosystem in most cases, and prevents fast growing coral like Staghorn or Table coral from out competing slow growing coral like Boulder or Massive coral. However, an increasing population of these predatory sea stars in one area can have a harmful effect on the health of a coral reef ecosystem. The Great Barrier Reef has had such an outbreak in recent years where the Crown of Thorns were thought to be consuming coral at a faster rate than its growth. This can indirectly affect marine species that rely on coral reefs for habitats, protection and food. Population ‘booms’ are thought to be caused by an increase in oceanic phytoplankton, which may in turn be caused by land run-off containing nutrient rich fertilisers from increased industrial farming methods. This allows many more Crown of Thorns larvae to reach maturity than naturally; and considering a single female can produce 65 million eggs in a single spawning season, this could become a huge problem of overpopulation if left uncontrolled.

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To prevent coral destruction in vulnerable areas, divers are starting to introduce a number of measures to control Crown of Thorns population sizes. Manual dismemberment is sometimes implemented, but ill-advised due to the likelihood of harmful contact in addition to the sea stars potential ability to regenerate. The most effective and humane way to reduce population sizes is through the injection of salts or chemicals that are deadly to sea stars, but pose no threat to other marine life. Coral scientists and conservation organisations are now even inventing autonomous sea star killing drones to help control population outbreaks and protect valuable coral reefs.

Species of the Month: Blue Spotted Ribbontail Ray

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The Blue Spotted Ribbontail Ray (Taeniura lymma) is a common species of stingray found from the tropical Indian Ocean to the Western Pacific Ocean. It lives in shallow reef habitats near shore to depths rarely deeper than 30 metres. It may be relatively small for a stingray at only about 35 cm across and 8o cm long, however, it is definitely one of the most distinctive and visually striking. Its yellow tinted circular body is covered in electric blue spots, with two stripes reaching along the tip of its protruding tail. Ribbontail Rays tends to be bottom dwelling, hiding under rock outcrops or hidden in the reef amongst the coral typically with only its tail showing. They are more commonly found roaming around out on sandy flats to feed on night dives.

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The Blue Spotted is one of a few rays which rarely buries itself in the sand, and therefore when seeing these rays kick up the sandy bottom, they are actually instead looking for prey. These rays feed on small bony fish, shrimp and other small marine species living in or on the sand. When caught, unlucky prey are trapped under the rays disc-shaped fins and pushed towards its mouth. Small rays such as the Blue Spotted are vulnerable to larger predators and are commonly preyed upon by larger marine species such as Sharks and the Bottlenose Dolphin. However, with shark populations decreasing worldwide, and the drop of shark sightings around Koh Tao, our rays are currently under very little natural threat. The Blue Spotted Ribbontail Rays also has a very effective defensive mechanism that can be used against threats in the form of two barbed, venomous spines on its lower tail. These can give humans an extremely painful wound, but fortunately these are only used as a last resort, and rays prefer to flee if threatened.

The blue spotted ray is still considered to be near-threatened by the International Union for Conservation of Nature (IUCN). This is due to large areas of its natural habitat being destroyed or collapsing due to environmental pressures alongside intensive fishing. Some are hunted for food, but a large quantity are actually captured for the pet trade as their stunning markings and small size make them seem ideal as aquatic pets. Unfortunately, most rays caught for the pet trade become ill; many outgrow their aquarium habitat or stop feeding due to external stressors and artificial surroundings. The methods used to catch them are also extremely harmful, such as cyanide fishing, which is harmful not only to rays but to all the species within the area and the environment as an ecosystem.

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It may still be a relatively common species today with a wide distribution, however, the IUCN still classify the Blue Spotted Ribbontail Ray as near threatened due to multiple factors. With a very low reproductive rate, long gestation times, and few offspring, this makes the Blue Spotted Ribbontail vulnerable to population depletion. Populations could collapse to the high demand for the pet trade alongside continuing habitat degradation worldwide and negative fishing practices.

This is another stunning marine life creature that can be found here on Koh Tao. Let’s all make sure we as divers do not aid in its habitat destruction by advocating for ocean protection and leaving marine species where they belong… in the ocean! Hopefully, many divers after us will then still be able to see this highlight of any dive.

[Photos by Adam Leaders: AdLePhoto]

Species of the Month: The Banded Sea Snake

 

Laticauda colubrine has a few different common names including  the Banded Sea Krait, Banded Sea Snake, Colubrine Sea Krait, and the yellow-lipped sea krait. They are easily identifiable by their distinct black bands encircling their light blue-greyish under-colour and yellow snout. Females are typically larger and can grow to around 150 cm in length, whilst the males only grow to around 100 cm; however, there have been reported sightings of Sea Snakes reaching a staggering 360 cm!

Unlike many species of sea snakes, the Banded Sea Snake have adapted and developed for a very amphibious lifestyle. They have also developed a salt gland under the tongue giving them the ability to expel excess salt absorbed from the marine environment. Their lungs are also proportionally larger than than lang snakes to allow Sea Snakes to stay underwater for 15 – 30 mins, up to a maximum of 2 hours! Although they are cylindrical in shape like most snake species, they have evolved with a compact, flat tail, a little bit like an oar, giving them the necessary propulsion for aquatic hunting. Common prey includes eels and small fish, and groups of Krait will often be seen working with parties of other predatory fish to capture their prey. Krait also have a unique defensive ability to fool potential predators into believing their tail is in fact their head when searching inside cracks and crevices.

Banded Sea Snakes are air breathing reptiles and return to land around every 10 days for digestion, mating, and the shedding of their skin. There are still some disagreements of how much time they spend on land compared to in the ocean due to the difficulty of accurately researching amphibious species.

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Although known for their venomous bite, which is 10 times as toxic as the rattle snakes, the number of recorded attacks is very low and the Banded Sea Snake is considered a very timid and docile animal, typically not aggressive unless dangerously threatened. Most venomous encounters actually occur on trawlers vessels whilst fishing as snakes get caught in the nets, and fishermen are occasionally bitten while releasing them. If bitten, envenomations (injection of the venom) is still very unlikely because venom stocks are complex to produce and are reserved for catching prey; therefore defensive bites are usually not venomous. In addition, a Krait can only open it’s mouth a very small distance and their fangs are extremely small, meaning they are almost of no threat to humans. If however, a venomous bite does occur, severe pain may be felt at the site of the puncture, respiration may weaken, and muscles may contract or cramp. A severe reaction may result in respiratory or cardiac failure and a need for emergency treatment and CPR. First aid includes washing the wound and applying a broad ligature between the injury and the body to slow the spread of the venom. Medical assistance should be called as soon as possible!

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At the moment, Banded Sea Snakes are not listed as a threatened species and there is very little work to be done in terms of protection and conservation. However, as fishing has rapidly grown worldwide and specifically in and around Thailand, it is estimated around 80 tonnes of different sea snakes are being caught intentionally or as by-catch every year. These snakes are often exported to other parts of Asia, commonly China and Vietnam, where they are consumed and considered a delicacy, used in medicines, or used to produce snakeskin leather goods.

The Banded Sea Krait is the only Sea Snake found around Koh Tao, and they are truly fascinating to find underwater. They can be found at many of our dives sites and are often spotted on shallower dive down to around 10 m depth. Keep an eye out on your next dive!

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Species of the Month: The Trigger Fish

 

The majority of dive sites here on Koh Tao are lucky enough to have a resident triggerfish or two. Out of a total of 40 species of Trigger, the three most common to Koh Tao are the Yellow-margin Trigger Fish (Pseudobalistes flavimarginatus), the Titan Triggerfish (Balistoides viridecens) and very occasionally the Clown Trigger Fish (Balistoides conspicillum). These beautiful, exotic, colourful fish are some of our favourites for many reasons and have an important role in the marine ecosystem.

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The Trigger Fish can grow up to 75 cm long, and gets its name from its first of three dorsal fins which when ‘triggered’ stands erect above its head like a horn. This is a sign of defensive aggression on behalf of the Trigger Fish whenever it feels threatened or provoked, often when a diver or predator enters its territory or ‘garden’. The Titan Trigger Fish is known to be especially territorial around mating season, and should therefore be viewed with caution from a safe distance. The anal and posterior fins rhythmically undulate from side to side to provide the main force of movement, whereas the sickle shaped tail fin, or caudal fin, is only used for speed when defending against or escaping potential predators. Other notable features include their small independently rotating eyes allowing them excellent 360 degree visibility and special awareness.

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The majority of Trigger Fish species are solitary for their adult lives, yet meet at set timetables according to moons and tides at traditional mating grounds. This is typically when species become the most territorial and potentially aggressive, and dominate a territory in the shape of a cone rising vertically. Therefore if ever attacked or chased by a Trigger Fish, try to swim away low and horizontally to escape their cone shaped ‘garden’ and do not swim up further into the cone. Also try to swim backwards which allows you to keep an eye on the Trigger Fish, and places your fins in-between yourself and any potential attack. The main defence to a Trigger fish is not to provoke one in the first place by respecting its personal space and keeping a watchful eye on its trigger. These really are beautiful fish so please don’t worry or avoid them, just respect and enjoy!

Unsurprisingly, Trigger Fish are known to show a higher level of intelligence that is unusual among fish and actually have the ability to learn from previous experiences. This is apparent when observing the deliberate way they examine their surroundings, contemplate possible food sources and methods of feeding all while staying aware of potential threats. Trigger fish in aquariums are also thought to recognise individual keepers and further understand human behaviours such as those associated with feeding and tank cleaning.

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Trigger Fish feed on a diet of bottom dwelling sea urchins, molluscs, crustaceans, and coral. You can often see them eating hard coral by clamping on with their strong jaws and ripping it apart by spinning and finning in various directions. This activity often stirs up nearby coral parts and small organisms, allowing other fish to feast on the leftovers. Trigger Fish play an important part on coral reefs by naturally pruning the coral, much like pruning roses.
You’re bound to see a friendly Trigger Fish or two while diving on Koh Tao, so admire their beauty, applaud their intelligence, but just remember to respect their garden!