* 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.
Wednesday, November 5, 2008
PREDATORS
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.
Large Grouper
The Nassau grouper is common resident in the waters off the Gulf of Mexico and the Caribbean. Some divers have been "bitten" by over friendly Nassau groupers that are used to human interaction in popular dive feeding sites. During feedings groupers occasionally will take the entire fist and forearm of unsuspecting diver into their large mouths. Grouper have several sets of teeth, placed in the mouth to act as raspers or holding teeth. The fish gulps down its prey using these raspers to prevent the smaller fish from escaping. The teeth are not used to tear or slash, as with barracuda or sharks. One can imagine the problem with this when considering that some of these fish grow to be as large as 800 pounds. These bites primarily result in loss of skin from the back of the hand and fingers, often followed by a severe infection.
Salt Water Crocadile
This endangered reptile actually is a danger to underwater enthusiasts and a number of people are killed and injured each year. It's hide has a very high commercial value because of its ease of skinning and because of this it is protected.
The saltwater crocodile is the largest living crocodilian species, growing to 6-7 meters in length and inhabits a very large area of northern Australia, Indonesia and Malaysia.
Treatment: Severe trauma or large predator injury (similar to head injury, limb injury due to falls, equipment crush, prop injuries). Call for help and immediate transport. Maintain open airway, keep face in nuetral position, be mindful of possible neck injury, direct pressure over bleeding wounds. Keep warm and treat for shock as needed.
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)
Monday, November 3, 2008
INJECTED TOXINS
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.
