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Jill Studholme
1,330 followers -
Writing on the marine environment and scuba diving
Writing on the marine environment and scuba diving

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Thailand limits number of divers visiting the Similans each day
Thailand’s Department of National Parks, Wildlife and Plant Conservation has said no more than 525 divers can visit the Similans on any one day. The decision was based on academic research that looked into the capacity of Thailand’s marine parks. Non-diving tourist numbers are also limited – to 3325 a day. Many tour operators opposed the move but the more responsible dive operators welcomed it.

“We fully support this conservation effort. It will mainly effect day trippers and fewer people will help the environment and make the Similan Islands more beautiful for everyone” commented Thailand Liveaboards

The measures are aimed to help the Similan islands recover and to promote eco-tourism.

As well as curtailing visitor numbers, the department has introduced a no single-use plastic rule and prohibited overnight stays on any of the islands.
https://news.scubatravel.co.uk/thailand-limits-divers-similans.html
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Diving Komodo on the Duyung Baru Liveaboard
Komodo has fabulous diving – sharks, turtles, manta rays, eagle rays plus nudibranchs and seahorses. The best way to dive it is by liveaboard, although you can take day boats from Labuan Bajo on Flores.

Which liveaboard to choose? You can’t go wrong with the Duyung Baru (https://www.scubatravel.co.uk/indonesia/diving-indonesia.html#DuyungBaru). For a start this liveaboard takes just six divers in three cabins. With the co-owner and dive guide Vovo Korth taking a dim view of crowded dive sites, often the seven of you will be the only people in the water.

Vovo’s wife Yani is the captain and cook. Her food is delicious, created with care and love. She gets up at three in the morning to make fresh bread for breakfast – from loaves to croissants. Not only a great cook, she is most friendly and welcoming.

Vovo bought his first boat in 1998 and called it the Duyung – Indonesian for mermaid. He has been sailing Indonesian waters ever since. When he and Yani started the liveaboard operation around Komodo only one other boat was operating, and Vovo made many exploratory dives. He has an intimate knowledge of the dive sites of Komodo with their wild currents, including a couple of “secret sites”.

The couple commissioned their current boat in 2011, calling it the Duyung Baru or New Mermaid.

Two double cabins and one twin cabin house the divers. There is plenty of storage space and ensuite shower and toilet. The beds are extremely comfortable. On the canopied deck are a sofa and chairs around a coffee table plus a sun terrace upstairs.

The boat is 27 m long with two masts – a beautiful looking craft. Nitrox is available.

Finally to the diving. This is world-class. Sharks and turtles on nearly every dive. Eagle and manta rays. Many huge shoals of fish. Corals in excellent condition. There are also dive sites for those liking the smaller stuff – seahorses and frog fish. The boat doesn’t have a set routine of dives – it depends on the type of dives that the divers on board want to do. If you really want to see that seahorse and not another manta ray, then you’ll have to sell it to your fellow divers.

The boat is only for experienced divers. Vovo likes you to have at least 75 dives. I would go further and say that you need to have experience of currents. The diving in many sites is not easy – the currents are fierce, especially at full and new moon (which is why there are so many large fish there). It is assumed you know what you are doing. At the beginning of the trip is an easy dive or two to practice using a SMB (surface marker buoy or “safety sausage”). Not until Vovo is satisfied that you can use the SMB will he take you on one of the the more challenging dives. That way if you should get separated from the group the tender will easily see you and pick you up.

Vovo is also a freediving instructor and there is an opportunity to take a freediving course if you wish. Although we dived with Vovo, on many trips one of his two experienced divemasters takes his place.

German, English and Indonesian are spoken.
https://news.scubatravel.co.uk/diving-komodo-liveaboard-duyung-baru.html
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Bodyguard - How Anemones Protect Hermit Crabs
Hermit crabs scuttle about the sea-floor using someone else’s shell for a home. They always use empty shells and never kill the original occupant.

When the crab becomes to large for its shell, it looks for another. When it finds a likely looking one it will try it on. If the shell doesn’t fit, or is too heavy, the crab returns to its old shell and continues it search.

Where there is a large population of hermit crabs and a shortage of shells, the crab will accept a sub-standard home: maybe a cracked or uncomfortable shell. But in good conditions it will be very particular about the new shell it chooses. Two hermit crabs will fight for the possession of an empty shell, or even a shell inhabited by one of the combatants.

Some of the Dardanas species of Hermit crab stick sea anemones on their shells. This camouflages the crab and the stinging cells of the anemone protects the crab from predators such as octopus.

The anemone also benefits from the arrangement. It becomes effortlessly mobile and shares the crab’s meals. However, if the crab is starving and can’t find anything to eat, it will eat the anemones, either from its own back or from the backs of other crabs.

Both partners are thought to participate in the transfer of the anemone to the shell. When the crabs change shells, they take their anemones with them.

Dardanas species are nocturnal with dark-adapted eyes. Look out for them on night-dives in the Indian and Pacific oceans, including in the Red Sea.

Further Reading : https://news.scubatravel.co.uk/creature-of-the-month-hermit-crab-dardanus-species.html

Photo credit: Tim Nicholson
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Ocean Art underwater photo competition 2018 is now open - anyone entering?
£75000 of prizes for amateur and professional photographers
https://news.scubatravel.co.uk/ocean-art-underwater-photo-competition-is-now-open.html
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Giant Manta Rays
Awesome to see underwater, the Giant Manta Ray is an enormous fish spanning nearly 7 m (22 feet). They live in warm waters around the world, gracefully flying through the water with steady sweeps of their giant wings.

Why are Mantas so Big?
Completely harmless filter-feeders, Manta rays use their head fins to direct plankton into their mouths. As plankton occur near the surface of the seas, that's where Mantas are also found. Filtering your food out of the oceans doesn't take much energy, which is why Manta rays can be so large.

Manta rays sometimes leap out of the water, falling back with a splash. This is thought to remove parasites, or perhaps be a show of territorial rights. However, Mantas collaborate when feeding and follow the plankton, so the latter seems unlikely.

Vulnerable in Spite of their Size
Until recently people believed there was only one species of Manta Ray: Manta birostris. Now though, researchers have observed that there are actually two: the Reef Manta Ray (Manta alfredi) and the Giant Manta Ray (Manta birostris). Both of these species have been classified as vulnerable in the IUCN Red List.

Mantas migrate vast distances, crossing international boundaries, in search of food. Products from manta rays have a high value in international markets, and targeted fisheries hunt them for their valuable gill rakers used in traditional Chinese medicine. Monitoring and regulation of the exploitation and trade of both manta ray species is urgently needed, as well as protection of key habitats.

Another factor which adds to the vulnerability of the Manta ray is its low reproductive rate. In the wild, females bear on average only a single pup every two to three years. Female mantas are thought to mature at around 8 to 10 years of age and to live to around 40 years.

Manta and devil ray catch increased from 900 tonnes to over 3,300 tonnes between 2000 and 2007.

Where to dive with the Giant and Reef Mantas?
Dive tourism involving Mantas is a growing industry. More money is made from live mantas than from the dead, caught mantas. A recent study estimates direct revenue to dive operators from manta ray dives and snorkels to be over US$73 million annually. Money made from associated tourism expenditures is put at US$140 million. However, tourism related industries can also negatively impact individual behaviour, entire populations and critical habitat. Tourism needs to be developed responsibly, with the needs of the animals respected.

Both species of Manta are found around the globe, their ranges overlapping in some places like Mozambique. It is difficult for a diver to distinguish between the two species. Both can be shades of black or white. They are also sometimes confused with the devil rays of the genus Mobula.

The Giant Manta Ray appears to be a seasonal visitor to coastal or offshore sites. While this species seems more solitary than the Reef Manta Ray, Giant Manta Rays are often seen aggregating in large numbers to feed, mate, or clean. Sightings of these giant rays are often seasonal or sporadic but in a few locations their presence is a more common occurrence. At certain times of the year you can see the Giant Manta Ray at aggregation sites such as the Similan Islands, Thailand; northeast North Island, New Zealand; Laje de Santos Marine Park, Brazil; Isla de la Plata, Ecuador; Cocos Island, Costa Rica; and Isla Holbox, Mexico. Being oceanic, you see them less frequently than the Reef Manta Ray.

The Reef Manta Ray lives from the Sinai Peninsula in the Red Sea to Durban, South Africa in the Western Indian Ocean, and from Thailand to waters off Perth, Western Australia in the Eastern Indian Ocean. In the eastern and south Pacific, the Reef Manta Ray occurs from the islands on Ryukyu Arc, Japan in the north to the Solitary Islands, Australia in the south and is sighted as far east as French Polynesia south of the equator and Kailua Kona, Hawaii north of the equator. Reef Manta Rays do not commonly venture from coastal waters, often moving between inshore cleaning stations and feeding areas. The Reef Manta Ray can reach 5 m across, however, most mature individuals do not exceed 4 m.

A good place to go to see reef mantas is Indonesia, particularly Bali and Komodo.
https://www.scubatravel.co.uk/mantaray.html
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There’s now an app for mapping seagrass, the oceans’ great carbon sink
A new online tool aims to crowdsource an image and location database of the world’s seagrass, in a bid to shed light on the threatened and fast-receding underwater flowering plants.
https://news.mongabay.com/wildtech/2018/06/theres-now-an-app-for-mapping-seagrass-the-oceans-great-carbon-sink/

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Ray is oldest diver in the world... aged 94

Inspiring story from the Express newspaper about the world's oldest scuba diver, according to the Guinness Book of Records.

https://www.express.co.uk/news/uk/967578/ray-woolley-oldest-diver-94-cyprus-navy-wartime-guinness-records
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Attack of the Clones: the secret life of Plumose Anemones
You often see small forests of Plumose anemones when diving in temperate waters. The is due to their ability to clone themselves.

Genetically different patches of clones are often separated by narrow paths free of anemones. Along the edges of these corridors, the anemones often possess two types of tentacle. One type for catching food and one much smaller type which can expand tremendously. They use these expanding tentacles to reach over and attack non-identical anemones across the border. The tip of the tentacle doesn't hurt anemones the same as itself, it only discharges its stinging nematocysts upon contact with a genetically different individual. After stinging the tentacle breaks, leaving about 1 cm of the tip attached to the victim. The tissue around the sting dies as, occasionally, does the victim.

Plumose anemones comprise a tall, smooth column topped with a crown of feathery tentacles. When they contact they look like swirly blobs.

Individuals are usually white or orange, although they are sometimes dark green, grey or brown in colour. They grow up to 30 cm tall and 15 cm across at the base. They like areas with currents so tend to live on prominent pieces of wrecks or on rocky pinnacles - in other words, in good diving areas

With fine, delicate tentacles they are unsuited to capturing large animals like fish. Instead they specialise in smaller prey such as small planktonic crustaceans. The anemone's columnar body is narrower just below the tentacles. A current will bend the stalk at this point and expose the tentacles broadside to the flow in the best position for feeding on suspended matter.

The Plumose anemone occurs from the Bay of Biscay (North of Spain) to Scandinavia in the northeast Atlantic, and on the west and east coasts of North America. It is unknown from the western basin of the Mediterranean but has been seen in the Adriatic, where it is believed to have been introduced. It has also been seen in Table Bay Harbour in South Africa where it was probably introduced from Europe.

Read the full story at https://www.scubatravel.co.uk/Plumose_19_4a.html


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15/04/2018
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Venomous sea creatures change their venom recipe often
Many animals use venom to protect themselves from predators and to catch prey. Some, like jellyfish, have tentacles, while others, like sea snakes, use fangs to inject their prey with venomous toxins.

For a long time scientists believed that an animal’s venom was consistent over time: once a venomous creature, always a venomous creature. However, through a close study of sea anemones, scientists have found that animals change their venom several times over the course of a lifetime, adapting the potency and recipe of their venom to suit changing predators and aquatic environments.

In a study published in eLife Science Magazine, Dr Yehu Moran of Hebrew University has and his team describe their spectacular findings. They studied the Nematostella sea anemones. They begin their life as tiny larvae and grow into animals measuring several inches long. While in the larvae stage, the Nematostella fall prey to larger fish but once mature, they become predators themselves, catching shrimp and small fish with their venomous tentacles.

While in the larvae stage, sea anemones produce uniquely potent venom that causes predators to immediately spit them out if swallowed. Later on, when the sea anemones grow big and become predators themselves, their venom adapts to their new lifestyle by producing a different kind of toxin, one best suited to catch small fish and shrimp. Over the course of a lifetime, as the Nematostella’s diet changes and they move from one aquatic region to another, they adapt their venom to suit their new needs and environment.

https://news.scubatravel.co.uk/venomous-creatures-change-venom-recipe-often.html

Research link:
Dynamics of venom composition across a complex life cycle, Yaara Y Columbus-Shenkar et al. eLife 2018;7:e35014 DOI: 10.7554/eLife.35014
https://elifesciences.org/articles/35014
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Still diving for conch shells at 94
Saw a very interesting program about Korea, featuring the Haenyeo. This group of women free dive for seafood, spending all day in the water. It's not calm coral waters but swell and seaweed. The oldest diver was 94 years old! Inspirational.
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