In addition to box jellyfish and cone shells there are a number of other hazardous creatures in the sea. Many can kill, although this often depends on the amount of venom used, individual reactions and the situation - if affected in deep water a victim may drown. Some basic first aid tips are given, although by far the best policy is not to meddle with these creatures.
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'.
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.)
Catfish, when interfered with,
produce three barbed spines which stick out at right
angles from the back and side fins. (It is not the
whisker-like sense organs around their mouths which cause
the damage.)
Stings from all these fish are painful and can lead to collapse and even death in exceptional circumstances. The venom in the spines remains active for days, so discarded spines and even refrigerated specimens should be treated with caution.
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.
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.
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.
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.
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.
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.
EDIBLE HAZARDS
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.
Ciguatera is 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.
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.
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 it is advisable to wash your hands
after handling these creatures.
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.