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Okinawa's Marine Hazards

OVERVIEW OF MARINE HAZARDS - Courtesy of University of Utah

There are a number of hazardous creatures in the sea. Many can cause serious harm to unaware or inattentive divers, swimmers, or shell collectors. Some may even cause death, although this often depends on the amount of venom used, individual reactions, nature of injury and location of accidents (deep water victims often drown). There are four major types of injury patterns from marine life. This presentation will list some, and basic first aid tips are given, although by far the best policy is not to meddle with these creatures.

Sea Anenomes and Sea Cucumbers

While most sea anemones are relatively harmless to humans a few do contain strong toxic substances producing quite severe effects. One of these is the stinging anemone (Actinodendron plumosum), a blue-grey to light brown animal which can look somewhat like a fir tree.

Found under boulders and coral, red bristle worms have numerous fine needle-like bristles which break off when they have become embedded in the skin, causing severe irritation.

Although sea cucumbers are one of the safest animals on the reef to touch, the numerous white Cuvierian tubules, which some eject when irritated, contain a toxin which can cause blindness if it comes into contact with the eyes. This toxin may also be present on the skin so you should wash your hands after handling these creatures.

STINGING CORALS

Although known widely as stinging or fire corals, these organisms are, in fact, colonial animals (Millepora sp) more closely related to hydroids. Having a hard coral-like skeleton, they vary in form from large upright sheets and blades to branching, finger-like 'antlers' with a yellow-green to brown colour. Effects and treatment are similar to hydroid stings.

CROWN-OF-THORNS STARFISH

The sharp spines of this creature are covered with a thin venomous skin which, if introduced into any wound can cause nausea, vomiting and swelling. Spines may also break off and remain embedded.

HYDROIDS

Looking like feathery plants, and sometimes referred to as fireweed, hydroids are actually colonies of animals equipped with strong stinging cells (nematocysts) used to capture prey and for defence. Some species can give quite severe stings causing inflammation, swelling and pain lasting up to a week. Effects may sometimes be more severe.

Divers are particularly prone to brushing against hydroids. Two species to avoid are this white, fine feathery one and the denser yellow/brown type. They can be found in fairly shallow reef areas and on structures such as wharfs.

BOXES OF DEATH - BOX JELLYFISH

Recognized as one of the greatest marine hazards, box jellyfish (Chironex fleckeri) kill more people than sharks, crocodiles and stonefish combined.

Each year, in late summer, the adult box jellyfish spawn at river mouths before dying. The fertilised eggs become tiny polyps which attach themselves to rocks in estuaries. In spring these polyps develop into little swimming jellyfish which migrate down rivers, especially with rains, to feed on shrimp. Unfortunately, they frequent beaches which humans also find attractive. The animal does not actively hunt, relying on food to bump into its tentacles. A struggling shrimp might tear a delicate jellyfish, so it needs to be killed instantly, on contact, with a very strong poison.

Tentacles, up to 60 in number and reaching 5m in length, are arranged in four groups at the corners of a box-shaped bell which can be as large as a basketball. The tentacles are armed with up to 5 000 million stinging cells known as nematocysts. These are triggered into action when stimulated by certain chemicals found on the surface of fish, shellfish and humans. Contact with just 3m of tentacles can kill an adult.

Recent studies have shown that the box jellyfish is able to see through four eyes, one at the centre of each side of the bell. How it processes this information without a brain is still a mystery but the animal is able to avoid even quite small objects. They probably try to avoid humans in the water, if given the chance; stings usually occur when people blunder into them. (They are almost invisible in the water.) It is certainly in the interest of the jellyfish to avoid turtles which eat them, apparently unaffected by the stings.

Another box jellyfish, Chiropsalmus quadrigatus, is generally less common than Chironex fleckeri, although it may outnumber them on Cairns to Port Douglas beaches. It is smaller, with slimmer tentacles, but the two are difficult to tell apart. There are about 20 species, worldwide, in the Cubozoa, or box jellyfish, family, Chironex fleckeri is the most lethal member.

IRUKANDJIS

Although it is more numerous in summer months, the irukandji (Corukia barnesi) can be found all year round and inhabits all waters. A member of the box family, it has one tentacle at each corner of its bell. It is tiny - only 2cm across the bell - but nonetheless packs a massive punch. Both bell and tentacles have stinging cells.

The actual sting is minor, but 20-30 minutes later the victim begins to experience agony which lasts for hours. Although not blamed for deaths its tendency to cause raised blood pressure can be dangerous for vulnerable victims. Ignoring the initial sting may also lead to some people suffering severe symptoms in deep water or while driving.

SEA URCHINS

It is just common sense to avoid the sharp black spines of the black sea urchin. They can penetrate deeply into the flesh and break off causing long-lasting inflammation if not removed – often surgically. There is doubt as to whether venom is also involved.

A less common but much more dangerous urchin is the flower urchin. Instead of long spines it appears to be covered with numerous flowers which are in fact little venomous pincers (pedicillariae) capable of causing paralysis and even death. It has killed several people in Japan.

Shell Fish

This derives from dinoflagellates contaminating shellfish (clams, scallops, oysters, etc.). The toxin, saxotoxin, is water soluble, heat and base stabile, and is therefore not affected by steaming or cooking. It inhibits sodium channels of excitable membranes, blocking propagation of nerve and muscle action potentials.

Symptoms: These usually occur within 30 minutes, and include parasthesias of the lips, tongue, gums and face. This process proceeds to the trunk and may progress to paralysis and respiratory arrest. The gastrointestinal form may appear hours or days after ingestion with nausea, vomiting, diarrhea and abdominal pain.

Treatment: No specific treatment. Stop eating if oral sensations are perceived. Empty stomach if systemic symptoms are noted, using emetic or lavage. Give respiratory support and monitoring if needed.

Scombroid

Occurs in tuna, mackerel, skipjack and other members of the family scombridae. Fish left at room temperature undergo bacterial breakdown of tissue histidine to histamine and saurine. Spoiled fish have a sharp, peppery taste.

Symptoms: Occur in the first hour, and a histamine-like intoxication is seen. There is headache, flushing, dizziness, palpitations and tachycardia. One may see hypotension, bronchospasm, urticaria and anaphylaxis. GI symptoms include nausea, vomiting, diarrhea, abdominal pain, thirst and dysphagia.

Treatment: Gastric lavage, respiratory and circulatory support. Antihistamines appear to be helpful.

Tetradoxin

Toad, or pufferfish, common in tidal creeks and coastal waters are well-known for their amusing habit of inflating their bodies with water or air to balloon-like proportions when provoked. Along with their relatives the porcupine fish, cowfish, boxfish, tobies and sunfish, their bodies contain the same toxin as the saliva of the blue-ringed octopus with the same, potentially fatal effects. Easily caught on fishing lines, they must never be eaten.

Derived from algae covered with bacteria Alteromonas sp.Being ingested by pufferfish The toxin concentrates in the liver and gonads. The toxin inhibits sodium transport, affects neuronal transmission in the CNS and periphery and also affects cardiac nerve conduction and contraction.

Symptoms: Entirely dose dependent-can have oral paresthesias, muscular fasciculations then a flaccid type of paralysis occurs. (curare-like).

Treatment: Gastric lavage and respiratory support, usually for 24 hours or more. Consider sedation because cognitive function intact. There will be spontaneous remission if the patient is otherwise supported.

Ciguatera

A form of food poisoning which occurs occasionally in certain coral reef fish. It originates in a tiny organism (dinoflagellate) attached to algae growing usually on dead coral. It is eaten by plant-eating fish and then accumulates in large predatory fish such as mackerel, coral trout and cod. The tasteless and odourless toxin is not destroyed by cooking or freezing.

All reef fish over 10kg should be treated with caution. Eat only a little and if symptoms develop discard the fish. Avoid internal organs of any reef fish. Symptoms, which begin 2-12 hours after fish are eaten, are varied and can include breathing difficulty requiring artificial respiration. If symptoms develop, induce vomiting.

CONE SHELLS

Happily for humans, the animals which inhabit the beautiful cone shells are nocturnal. Hunters by nature, many carry a toxic concoction which is capable of killing humans; in fact, the venom from one geographer cone (Conus geographus) is capable (in theory of course,) of killing 700 people.

There are about 80 species of cone shells in Australia, mostly in tropical waters. Some feed on worms, some on molluscs (including other cone shells) and some on fish. It is the last two types which are most dangerous to humans. To stop a fish in its tracks a snail needs a formidably fast-acting venom.

It is thought that the cone detects its prey from chemicals in the water drawn through its siphon. Some visual sense may also be involved. The cone then extends its proboscis, a hollow feeding tube, on the end of which is a hollow, barbed tooth. Attached to a poison sac, this tooth is driven harpoon-style into the hapless victim, poison being injected through the tooth. The force of the harpoon has been known to penetrate a periwinkle shell. Each tooth is used only once. A supply of spares is kept in an internal tooth sac and moved into position as required. Held by the barbed tooth, the victim is quickly immobilised by the poison and then drawn into the expanded proboscis to be digested. A mollusc victim may be sucked from its shell (certain toxins may loosen its muscular attachment to the shell, making the task easier).

The best way to avoid stings is not to touch live cone shells. The extendable harpoon-wielding proboscis is capable of reaching most parts of the shell so it is not safe to grip the wide end. Thick shoes should be worn for reef walking and cones should never be put in pockets or sleeves. Sting symptoms progress from numbness to breathing failure.

BLUE-RINGED OCTOPUS

This potential killer is small, the northern (larger) species reaching only 20cm across spread tentacles. It is normally yellowish brown but when disturbed its blue rings become bright and obvious. It is not aggressive by nature but will bite when provoked.

The venom is contained in the saliva, which comes from two glands each as big as the animal's brain. It has two components. One is probably most effective on crabs (its main prey) but relatively harmless to humans while the other, the same as that present in toad/puffer fish, probably serves as a defence against predatory fish. Humans, when bitten, usually do not feel the bite but soon notice a numbness around the mouth followed quickly by paralysis. Death can result from respiratory failure.

This octopus lives in shallow water, typically in sheltered rock pools and crevices, cans and bottles. Never put your hands where you cannot see them. The venom is not injected but enters the wound in saliva. Washing the bite may therefore remove venom from the surface.

STINGRAYS

Stingrays will defend themselves by lashing out with whip-like tails equipped with one or two spines. Because they are barbed they can cause serious gashes and in about two-thirds of species they are also venomous. The spines are capable of penetrating wetsuits and shoe leather and have been known to kill people unlucky enough to have been stabbed in the chest.

Those at risk are people wading, who often get injured on the leg, careless fishers and divers who may get lashed by a startled stingray as they swim above it. Prevention involves shuffling feet when wading. Wash wounds thoroughly with sea water and remove spines carefully.

VENOMOUS FISH

A number of other fish are equipped with similar venomous spines, although they are more mobile than stonefish and will prefer to get out of the way. These include members of the scorpionfish family, such as this popular aquarium fish known by many names such as lionfish, butterfly cod and firefish. (The freshwater bullrout is also in this family.)

STONEFISH

The stonefish's lifestyle makes this, the most venomous fish in the world, particularly dangerous to unwary humans. Lying on the seabed, looking exactly like an encrusted rock, it waits for small fish and shrimps to swim by and then, with lightning speed, opens its mouth and sucks them in. The whole ambush has been timed at just 0.015 seconds.

Vulnerable to bottom-feeding sharks and rays, it has developed a defence - a row of unlucky 13 venomous spines along its back. It is, in fact, the victim who injures him/herself. Each stonefish spine is encased in a sheath containing bulging venom glands. Downward pressure on the spine causes the sheath to be pushed back, the venom from the pressurised glands shooting forcefully up grooves on the surface of the spine into the deepest part of the wound. (It takes a few weeks for the glands to regenerate and recharge.)

Victims become frantic with pain which lasts for hours. Temporary paralysis, shock and even death may result. Stonefish may be found from exposed sand and mud in tidal inlets to depths of 40m. Prevention involves wearing thick-soled shoes and treading gently - spines may penetrate soles if a stonefish is jumped on. Also, take care when turning over 'rocks'.

SEA SNAKES

Sea snake venom is more toxic than that of land snakes, however these animals pose little risk. Most are shy and stay away from people, biting only when provoked, if at all. Even then they tend not to use their venom.

It is reserved for quickly immobilising prey, not for defence. In fact, about 65% of bites are 'blanks'. Nevertheless, the potential danger of a sea snake should not be underestimated and they should be treated with respect.

Sea snakes are air breathers probably descended from a family of Australian land snakes. They inhabit the tropical waters of the Indo-Pacific and are highly venomous. Thirty-two species have been identified in the waters about the Barrier Reef in Australia. They seem to congregate in certain areas in the region about the swain Reefs and the Keppel Islands, where the olive sea snake (Aipysurus laevis) is a familiar sight.

Sea snakes have specialized flattened tails for swimming and have valves over their nostrils which are closed underwater. They differ from eels in that they don't have gill slits and have scales. Due to their need to breathe air, they are usually found in shallow water where they swim about the bottom feeding on fish, fish eggs and eels.

The yellow-bellied sea snake ( Pelamis platurus ) is planktonic, and is seen on occasions floating in massive groups. Fish that come up to shelter under these slicks provide food for the snakes. Occasionally these yellow-bellies get washed up on beaches after storms and pose a hazard to children.

Aggressive only during the mating season in the winter, the sea snake is very curious, and they become fascinated by elongated objects such as high pressure hoses. Advice here is to inflate your BC so as to lift away from the bottom and the snake. Provoked snakes can become very aggressive and persistent --requiring repeated kicks from the fins to ward them off.

Persistent myths about sea snakes include the mistaken idea that they can't bite very effectively. The truth is that their short fangs (2.5-4.5mm) are adequate to penetrate the skin, and they can open their small mouths wide enough to bite a table top. It is said that even a small snake can bite a man's thigh. Sea snakes can swallow a fish that is more than twice the diameter of their neck.

Most sea snake bites occur on trawlers, when the snakes are sometimes hauled in with the catch. Only a small proportion of bites are fatal to man, as the snake can control the amount of envenomation, a fact probably accounting for the large number of folk cures said to be 95% effective.

Intense pain is not obvious at the site of the sea snake bite; 30 minutes after the bite there is stiffness, muscle aches and spasm of the jaw followed by moderate to severe pain in the affected limb. There follows progressive CNS symptoms of blurred vision, drowsiness and finally respiratory paralysis. A specific antivenin is available; if not obtainable-the Australian tiger snake antivenin or even polyvalent snake antivenin can be used.

Barracuda

The barracuda is any of about 20 species of predatory fishes of the family Sphyraenidae (order Perciformes). Barracudas are usually found in warm, tropical regions; some also in more temperate areas. They are swift and powerful, small scaled, slender in form, with two well-separated dorsal fins, a jutting lower jaw, and a large mouth with many sharp large teeth. Size varies from rather small to as large as 4-6 feet (1.2-1.8 meters) in the great barracuda (Sphyraena barracuda) of the Atlantic, Caribbean, and the Pacific.

Barracudas are primarily fish eaters of smaller fishes, such as mullets, anchovies, and grunts. They are good, fighting sporting fishes, and the smaller ones make good eating. In certain seas, however, lately increasingly they may become impregnated with a toxic substance that produces a form of poisoning known as ciguatera.

Barracudas are bold and inquisitive, and fearsome fishes, that may be/are dangerous to humans. The great barracuda is known to have been involved in attacks on swimmers. In Hawai'i, they have been known to inhabit open waters and bay areas in the shadows, under floating objects. To avoid them, don't wear shiny objects. They are attracted to shiny, reflective things that look like dinner. They cause harm with their sharp jagged teeth and strong tearing jaws; slashing and creating jagged tears in your skin. Should you or another be hurt by one get medical treatment.

Stop any bleeding and treat for shock by keeping yourself or the victim calm and warm.

Moray Eels

A number of divers have been bitten by moray eels, their sharp teeth designed to lock on to prey sometimes causing severe damage. These eels are not, by nature, aggressive towards people but can attack if provoked. Many attacks can be blamed on the foolish practice of fish feeding by hand. Accustomed to receiving handouts, some approach divers on sight and can bite a hand which they believe to be holding food.

For the same reason divers have also been approached aggressively by potato cod, wrasse, gropers and other fish expecting handouts of food. While some of these may not inflict injuries there is the additional threat that novice divers may be frightened into acting unwisely. The best prevention is to abide by the GBRMPA fish feeding guidelines which forbid the hand-feeding of fish.

Sharks

What do you think of first when you think of sharks? Fearsome, big teeth, and unprovoked attacks on swimmers. Sharks, however, have many other interesting features that make them stand out from other denizens of the sea. The main difference from other fishes is that their skeleton is made from cartilage rather than bone. This cartilage makes sharks very flexible, allowing them to twist 360 degrees and whirl around and bite an unsuspecting diver or fisherman.

Sharks don't have an air bladder, and if they stop swimming they will sink. To overcome this disadvantage, they have very large, oil-filled livers giving them some buoyancy. An advantage of not having a swim bladder is that it gives sharks great vertical mobility allowing them to rapidly move upward in the water column without the development of bends. In addition, their pectoral fins act as glide-planes and provide great lift as the shark swims.

Sharks have many other interesting characteristics. Shark meat has an unpleasant taste due to the presence of high concentrations of the waste product urea in the tissue. Sharks store urea to maintain an osmotic balance with seawater so as not to have a water loss problem. Shark reproduction is very different from that of most bony fishes, having a very low output from their internal fertilization and production of large young. Sharks also have very low growth rates, a problem that is compounded by overfishing. An interesting sense that sharks possess is one called electroreception. There is a system of jelly-filled pores around the head and mouth called "ampullae of Lorenzini" that can detect small electric fields of less than 0.01 microvolt. This has been used to develop a small shark repelling apparatus for divers to wear that seems to be effective in warding off sharks.

Sharks can see color, as indicated by the presence of cone cells in their retinas. Similar to cats, they have a light-reflecting layer to enhance their night vision. This is important to divers to realize that swimming and diving in shark infested waters at night is more dangerous. The reason that chumming works so well in attracting sharks is their acute sense of smell. This could be a warning not to dive with even the smallest cut or abrasion. The most economically important sharks are the sandbar, bull, and lemon which do not mature until about 12 to 18 years of age. Slow growth is the norm; for example, a tagged immature male sandbar shark was recaptured 15 years later and had only grown about 19 inches and was still immature.

Sharks do not attack humans for the sole purpose of hunger. In fact, sharks do not know what the feeling of hunger is, and in fact, can go for many months without eating. This is not to say that sharks do not attack with the intention of seeking prey. Many attacks on divers and surfers especially can be attained to searching for food. To a shark, a surfer on a surfboard slightly resembles that of a seal or sea lion, or a diver in a black wetsuit can look like other prey.

Sharks also attack humans because they have been provoked or agitated by the person. Many spear-fishers have been attacked by reef sharks because when they spear fish, the blood from the fish and it's vibrations can sometimes result in a feeding frenzy by many sharks. Bright colours can also be counted for attacks. As many people have believed in the past, sharks do in fact can see colours, and do indeed have very good eyesight. Avoid wearing the colours of orange and yellow, as this can aggravate the shark, and possibly lead to attacks. Sharks are in fact attracted by splashing and vibrations in the water, and it can sometimes be attributed to attacks. Most scientists have not been able to predict why and where sharks attacks.

The following is a list of preventative measures you, as a swimmer or diver can do to prevent the possibility of shark attacks:

• Do not tease or entice sharks!
• If you cut or injure yourself... get out! Do not stay in the water with blood around you. Sharks can smell blood from over a mile away. And, for the women who read this, if you are in the middle of your menstrual period, please stay out of the water for your own sake.
• Watch other fish and turtles in the area--if they start acting erratic--be alert that a shark might be in the area.
• Do not swim in waters that have been deemed dangerous. Avoid swimming in murky waters. If you feel something brush up against you.... get out of the water to check to make sure that you have not been bitten. Many shark attack victims have noted the lack of pain from being bitten, doctors and scientists have not been able to conclude why this occurs.. so if you have been brushed against by something, get out and investigate. Finally, if you don't feel right in the water. Then get out! Nothing can be said for "gut feeling."
• Watch other fish and turtles in the area--if they start acting erratic--be alert that a shark might be in the area.

Most shark attacks are fortunately not fatal, however, there are a percentage of attacks that are fatal. There are only 4 sharks who consistently attack people: The Great White, The Tiger, The Bull, and The Oceanic White Tip. There are, however, other large sharks that have attacked humans, and can potentially dangerous.

When most sharks attack, the first bite is usually a "tester." Like most people, when sampling food, they bite once, revel in the taste, and then decide whether or not to continue... with most sharks, sampling occurs as well. The trouble is, with the sampling of a Great White or other larger predatory sharks, the first bite is so massive or severe that many people die from their injuries, and do not actually die from being consumed. A lot of fatalities can be attributed to people bleeding to death or dying from shock.

There are different modes of shark attacks and investigations that sharks go through when they come across humans. The following list shows what a shark can do when it comes across a human.

• Indifference (rare)
• Approach with swift visual inspection from a distance without follow-up
• Approach with surveillance circling - without follow up or follow-up, contact and attack
• Approach with brush-past, without follow-up (wounding possible)
• Charge with collision (upwards trajectory generally)
• Charge with single or double investigative bite without tearing
• Charge with biting and removal of flesh (death in 45% of cases)
• Multiple feeding-frenzy charge (death in 100% of cases)

FACTS & STATS ON MARINE HAZARDS

Box jellyfish have been known to kill people within three minutes, blue-ringed octopus in 30 minutes and pufferfish (eaten) in 17 minutes.

At least 65 people have been killed by box jellyfish in the last century, over 30 of them on beaches between Mackay and Cairns.

Aboriginal people long knew about box jellyfish, but it was not until after the death of a five-year-old boy at Cardwell, in 1955, that Chironex fleckeri' was identified by scientists. The irukandji (Carukia barnesi) was first scientifically identified in 1961 by Cairns doctor, John Barnes. He named it after the local Irukandji Aboriginal people.

Toad/pufferfish are not only poisonous to eat but can, with their beak-like mouths, remove toes and fingers. Ancient laws worldwide forbade consumption of these species - fish without scales are classed as 'unclean' in the Old Testament.

At the base of the tails of the aptly named surgeon fish are razor sharp blades which can inflict nasty cuts. No venom, however, is involved.

You are more likely to die from a box jellyfish sting than a shark attack. Reef sharks are not normally aggressive to humans but should be treated with respect. Do not carry bleeding fish and avoid swimming after dark.

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