Sunday, February 23, 2014

Frilled Shark

The frilled shark (Chlamydoselachus anguineus) is one of two extant species of shark in the family Chlamydoselachidae, with a wide but patchy distribution in the Atlantic and Pacific Oceans. This rare species is found over the outer continental shelf and upper continental slope, generally near the bottom, though there is evidence of substantial upward movements. It has been caught as deep as 1,570 m (5,150 ft). In Suruga Bay, Japan it is most common at depths of 50–200 m (160–660 ft). Exhibiting several "primitive" features, the frilled shark has often been termed a "living fossil". It reaches a length of 2 m (6.6 ft) and has a dark brown, eel-like body with the dorsal, pelvic, and anal fins placed far back. Its common name comes from the frilly or fringed appearance of its six pairs of gill slits, with the first pair meeting across the throat.

Seldom observed, the frilled shark may capture prey by bending its body and lunging forward like a snake. The long, extremely flexible jaws enable it to swallow prey whole, while its many rows of small, needle-like teeth make it difficult for the prey to escape. It feeds mainly on cephalopods, leavened by bony fishes and other sharks. This species is aplacental viviparous: the embryos emerge from their egg capsules inside the mother's uterus where they survive primarily on yolk. The gestation period may be as long as three and a half years, the longest of any vertebrate. Litter sizes vary from two to fifteen, and there is no distinct breeding season. Frilled sharks are occasional bycatch in commercial fisheries but have little economic value. The International Union for Conservation of Nature (IUCN) has assessed it as Near Threatened, since even incidental catches may deplete its population given its low reproductive rate. This shark, or a supposed giant relative, is a suggested source for reports of sea serpents.

With its elongated, eel-like body and strange appearance, the frilled shark has long been likened to the mythical sea serpent. The head is broad and flattened with a short, rounded snout. The nostrils are vertical slits, separated into incurrent and excurrent openings by a leading flap of skin. The moderately large eyes are horizontally oval and lack nictitating membranes (protective third eyelids). The very long jaws are positioned terminally (at the end of the snout), as opposed to the underslung jaws of most sharks. The corners of the mouth are devoid of furrows or folds. The tooth rows are rather widely spaced, numbering 19–28 in the upper jaw and 21–29 in the lower jaw. The teeth number around 300 in all; each tooth is small, with three slender, needle-like cusps alternating with two cusplets. There are six pairs of long gill slits with a "frilly" appearance created by the extended tips of the gill filaments, giving this shark its name. The first pair of gill slits meet across the throat, forming a "collar".

The long jaws of the frilled shark are highly distensible with an extremely wide gape, allowing it to swallow whole prey over one-half its size. However, the length and articulation of its jaws means it cannot deliver as strong a bite as more conventionally built sharks. Most captured individuals are found with no or barely identifiable stomach contents, suggesting a fast digestion rate and/or long intervals between feedings. This species preys upon cephalopods, bony fishes, and smaller sharks.

The frilled shark has seldom been encountered alive, and thus poses no danger to humans (though scientists have accidentally cut themselves examining its teeth). On August 27, 2004, the first observation of this species in its natural habitat was made by the ROV Johnson Sea Link II, on the Blake Plateau off the southeastern United States. On January 21, 2007, a Japanese fisherman discovered a 1.6 m (5.2 ft) long female alive at the surface, perhaps there because of illness or weakness from the warm water. It was brought to Awashima Marine Park in Shizuoka, where it died after a few hours.

Japanese fishers regard it as a nuisance, as it damages the nets. This shark is sometimes sold for meat or processed into fishmeal, but is not economically significant. Because of its very low reproductive rate and the continuing expansion of commercial fisheries into its habitat, the International Union for Conservation of Nature (IUCN) has listed it as Near Threatened.


Kathy Dowsett

Tuesday, February 11, 2014

Diver checks off item on 'bucket list' with Bonaire dive

One item on my "bucket list" was to dive in Bonaire -- mission accomplished.

Along with Aruba and Curacao, Bonaire is one of the ABC Islands that are the western-most islands of the Leeward Antilles in the Caribbean, north of Venezuela.

Bonaire's licence plates proudly declare that it is a "Diver's Paradise" and after experiencing the underwater beauty off its coast, I can vouch for that claim.

There are more than 60 dive locations along Bonaire's shoreline. We dove the West Coast, which is calmer than the East Coast (known as the wild side), where more adventurous divers go for a different dive experience.

While on a recent cruise ship vacation, Bonaire was one of our six stops and I was excited to dive there in the clear blue water with a temperature of 28 degrees Celsius. I disembarked the ship at Kralendijk, the main town of Bonaire, where I was greeted by Claire Crowe, who volunteered to take me shore diving. My own personal guide! Luckily for me, Claire’s mother-in-law is a personal friend of mine.

We walked along the shore until we reached the Sponge Bob dive site, which is in front of Yellow Submarine, one of five PADI certified dive shops run by Dive Friends Bonaire. If you're looking to rent gear, take a course, or have your own personal guide, they have it all. Their staff is friendly and welcoming.

After gearing up, we proceeded down the "pool area" and slowly descended to our goal of 45 feet. The slower start and descent works better for me as there is minimal current. It makes for an enjoyable dive all around. Equalizing was not a problem as it can be on boat dives. The marine life was abundant and the trumpet fish put on a great colourful show.

There were Cleaner Shrimp, Porcupine fish, Yellowtail Snapper, a gang of Blue Tang, Cow fish, Squirrelfish, French Angle, Rock Beauty, Honeycomb Cowfish, Whitespotted Filefish and Scrawled Filefish. There were also various corals and sponges, such as Brain, Purple Vase, Sea Fan and Staghorn coral. The anemones, like the Giant Anemone, Social Feather Duster and Christmas Tree Worm were everywhere. Visibility was unlimited.

In order to protect the coral, Bonaire does not allow dive gloves or knives unless part of a dive clean-up program. Make sure you have the correct buoyancy to avoid contact with the coral.

Noticeably absent were the lion fish. Bonaire is trying to control this invasive species (STINAPA) with a lion fish hunting program so if you ever have the chance to dine on Lion Fish please do!

Bonaire is also a snorkelers paradise. Everyone from children to adults can enjoy the beautiful sights from the crystal clear water at the surface.

Some interesting facts about Bonaire: It was discovered in 1499 by the Spanish and became a Dutch island in 1633. It is known as the "Fish Capital of the Caribbean" and "Arizona by the Sea." Flamingos are the island's national symbol. Harvesting of salt has been a major industry on Bonaire for more than 350 years. The Caribbean sea here is as much as 5.2 miles deep. Bonaire was part of the Netherlands Antilles until Oct 10, 2010, when it became a special municipality of the Kingdom of the Netherlands.

The official language on Bonaire is Dutch, while the local language is Papiamento, which is a mixture of Portuguese, Spanish and Dutch. English is widely spoken on the island and the U.S. dollar is the official currency.

We finished our dive after about 40 minutes. Time flies when you are having fun. It was a grand day of diving in Bonaire and I would like to thank Claire for her great "guiding" and Dive Friends Bonaire for their wonderful hospitality. If you're headed to Bonaire, contact them. They are a wealth of information, and will make your "bucket list" come true, like it did for me.

Kathy Dowsett

Thursday, February 6, 2014

Tips For Beginner Scuba Divers: How To Control Panic or Anxiety Attacks Underwater

Although under water anxiety attacks are common events in scuba diving, most beginner scuba divers may not know how common they are until they start taking their training classes. So, instructors who want to keep their classes safe from harm usually advise their students of the frequency and how to handle them if they occur while they are under water.

Divers who have had these experiences may describe the attacks as a sudden panicky feeling when they realize that they are under the water and a great distance away from dry land. In many cases, these fears are often unprovoked since there are no real threats surrounding them. Therefore, it is important for each diver to know how to handle the anxiety attacks if or when it happens to them. According to Dr. Richard D. Telford, author of Take Care of Yourself, one of the most important skills an individual may have in life is controlling the anxiety instead of letting it control the individual. By taking control of the anxiety, it will prevent the stressful situation from progressing into a full-blown panic attack. Listed below are some invaluable tips that people can use to remain safe.

Confront the Anxiety Before The Dive

Beginner divers should start by controlling their fears before leaving home. This can be accomplished by asking numerous questions that relate to the individual's capabilities and desires. For instance, is the person mentally and physically prepared to make the dive? Or, is this really the individual's idea of having fun? If the person finds that they are having problems with responding appropriately to these practical questions, they should not make the dive. Specifically, in cases where the person may feel that the dive is beyond their physical capabilities.

Express Feelings to Divemaster

If the beginner diver decides to take the dive but they are still feeling a little anxious, the individual should let the divemaster know what they are feeling. Since the divemaster's role is to keep the divers safe, they can pair these divers with a buddy so that they can assist. One of the buddy's primary functions is to help with carefully walking the person through the dive. For instance, the buddy may start their dive off by checking the reliability and safety of the scuba diving equipment. While this strategy may appear to be insignificant, the purpose is to help allay the fears of the individual because these are normally some of the actual thoughts that race through their mind.

Preventing Anxiety Underwater

The real test, however, begins when the individual is under the water since this is where the actual panic attack normally happens. Therefore, one of the best ways the buddy can help to keep the anxiety at bay is to focus the individual's mind on enjoying the diving experiences. One of which is looking at all of the beautiful scenery that surrounds them when they are swimming around. Also, to make the experience completely trouble-free, the buddy diver should not take the beginner in caves or other places that can provoke normal fears to occur. Instead, buddy divers may want to leave the cave experience until the diver becomes more comfortable under the water. In fact, future dives will always allow time for branching out into the deep.

While underwater anxiety attacks are common among many beginner scuba divers, there are ways to minimize the impact and keep the beginner safe from harm. One of the most common methods used is pairing the diver up with a buddy so that they can walk the person through these experiences.

Kathy Dowsett

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