Sharks have inhabited the world for over 400 million years but they mature almost at the same rate as humans, very slow for a threatened species. It means that some of the species cannot reproduce fast enough to replace the number of sharks killed by humans.
Family with only three species: thresher shark, Bigeye thresher, Pelagic thresher.
Ampullae of Lorenzini
A unique, highly specialized bioelectrical system existing of tiny fluid- filled pits located in the front of the head, containing receptor cells. The electrical current given off by all creatures is detectable by these ampullae, but in addition to finding prey, they may also allow the shark to navigate relative to the ocean currents and earth’s magnetic fields.
The unpaired fin on the underside of the body behind the anus in sharks, located between the pelvic fin and the caudal fin.
A word creation by Dr. Erich Ritter, a combination of Angst (Fear) and Fascination which describes exactly the mixed feeling of people when they talk or think about sharks.
Closer to the head.
Sharks are at the top, or apex, of the food chain in the oceans. These Apex predators maintain the balance and biodiversity of the marine ecosystem.
Armored fish with lengths of over 20 feet (6 meters).
Body Language of Sharks
Reading their minds, observing their movements. Some sharks may be swimming in threat postures if they are approached too closely or when cornered. With its jaws slightly open, this is a warning by the shark to divers that it will attack if pursued. However, it could be nothing else but yawning.
Often young sharks (and other marine life) that are caught by mistake and therefore never have the chance to reproduce. They are caught by long line vessels who are fishing for tuna for example. Most of those animals die and are thrown back, the sharks are finned and often thrown back alive. Hundreds of thousands are being “accidentally” killed annually this way.
The early developing dogfish embryo is contained in thin amber- colored membranous egg cases, which are called a “candle”.
Ground sharks, 8 families, 48 genera, 209 species. Most charcharhiniformes have a wide mouth, a third eyelid called nictitating membra- ne, sharp edged teeth, two dorsal fins, no spines, an anal fin and five gill slits. They exhibit all three types of reproduction forms found in sharks.
Cartilage is what the skeleton of sharks is made of. It’s a kind of con- nective tissue; strong enough to give support, and may become calci- fied. It has the advantage of better buoyancy and flexibility than bone. It might have contributed to the fact that sharks have virtually remai- ned unchanged for millions of years.
Pertaining to the tail region.
The tail fin, it is the most important fin for propulsion and it takes on very specialized forms in different species.
A longitudinal, fleshy ridge along the side of caudal peduncle.
Toward the head.
Harbor porpoises, dolphins.
Fishes with cartilaginous skeletons, skull, teeth and vertebrae, which are heavily calcified.
a) Elasmobranchii – Sharks, rays, skates, possessing five to seven gill slits or gill openings.
b) Holocephali – Chimaeras, a small group of fish that live in deep cool waters, and have only one gill opening.
Poisoning from eating the liver of the whitetip reef shark and inver- tebrate filter-feeders.
Convention on International Trade in Endangered Species of Flora and Fauna.
Oldest known ancient shark, less than 6 feet long, lived 400 milli- on years ago. Impressions of skin, kidneys and muscles were found in shales off shore of Lake Erie. It disappeared 290 million years ago.
Rod-like structures used for mating, each male has two, which are cy- lindrical extensions of the pelvic fins. They are used to transport sperm to the female.
A collecting chamber for the digestive, urinary, and reproductive systems that opens externally between the pelvic fins, also called cloacal opening.
A broad expanse of ocean bottom that slopes gently from the shoreli- ne to the shelf break (at a depth of about 200 meters or 600 feet) at the edge of which the continental slope drops steeply to the ocean floor.
A region of the outer edge of a continent between the shallower con- tinental shelf and the deep ocean floor – divided into the upper-slope (200 – 650 meters or 600 – 2,000 feet), mid-slope (650 – 1,500 meters or 2,000 – 4,500 feet), and lower slope (below 1,500 meters or 4,500 feet); the top of the continental slope is usually marked by the 200 meters (600 feet) isobath.
Pandarus species, often attached to the pectoral fins of sharks. Remo- ras feed on these parasites.
The back (dorsal surface) is darker than the belly, which makes the shark difficult to see from both above and below
Projection (point) on a tooth; many teeth have just one large cusp but some have additional side cusps.
Found on or near the bottom of the sea or other aquatic habitat.
Hard, tooth-like, placoid scales embedded in the skin of sharks giving
most sharks a rough sandpaper-like feel. Each shark species has a different pattern. It improves the hydrodynamics which means that it helps surface and skin friction reduction.
Prey is usually swallowed whole. The stomach produces strong acid
to break down food, then the indigestible things like bones are regurgitated.
The combined head, trunk and enlarged pectoral fins of some sharks and rays with dorsoventrally (from the back to the belly) flattened bodies.
Diseases in Sharks
Mostly found in captive sharks such as: parasites, bacterial, and liver diseases. However, tumors are rare in sharks but 20 cases in captive sharks have been reported: meningitis, a thyroid tumor in a dogfish, a tumor in a cat shark as well as a leukemia type of tumor in a sandbar shark have also been reported.
The upper surface of the body or head.
The unpaired fin or fins along the upper body. The anterior fin is usu- ally larger than the posterior. Research indicates that when dorsal fins cut through the sea’s surface they may be detecting pressure waves asso- ciated with activity nearby, such as a struggling animal. Lemon sharks have two dorsal fins which are the same size.
In a dorsoventral direction; “The ray has a dorsoventrally flattened body.” (from back to belly)
Sharks obtain their body heat from the outside.
Sharks, skates and rays.
Scientist who studies sharks, rays and chimaeras.
A developing pup before birth or hatching.
Humanity has put many shark species at risk. In some cases species have fallen by 75 to 90% within recent decades.
Confined to a localized area; a species endemic to a certain area is not found anywhere else.
Sharks that contain a constant body temperature, capable of genera- ting heat within the body by metabolism or other methods.
Sharks basic bodies have changed very little in the last 400 million years, and have not changed at all during 30 million years, demonstra- ting a highly evolved body.
Ten times more sensitive to light than man. They see color, making distinctions between objects in dim light as well as at night due to “ta- petum lucidum,” a light reflector behind the retina. Some sharks have a nictitating membrane, which covers the eye like a third eyelid. Pupils vary in size and shape among different species of sharks. New research shows that sharks are far-sighted.
Numerous stimuli in the water such as abundance of prey, blood, irre- gular movements, and struggling fish can trigger this type of behavior. The brain becomes overloaded with sensory cues, so that animals lose all inhibitions. Not unusual in mob riots of humans either.
Females of many shark species grow larger than males.
The cutting-off of fins for shark-fin soup. The sharks are then thrown back into the sea alive where they will die a terrible death. 7,000 metric tons of dried shark fins are traded annually worldwide. 6 foot fins of the whale shark can bring as much as $15,000. A very inhumane and brutal method, which must be stopped.
Shark fisheries search for meat, fins, oil and skin. They are responsible for most of the “by-catch” in fishing nets and long lines. The biggest problem is finning and the waste of the by-catch.
The length of a shark measured from the tip of the snout to the posterior edge of the fork of the tail.
Organic matter being gradually replaced by minerals.
Water that is not salty.
Period of development of the embryo within the female. Spiny dog- fish have perhaps the longest gestation period of all sharks: 22 to 24 months, longer than that of elephants.
They extract the oxygen from the water, running through the mouth over the gills. At the same time the gills expel the excess of carbon dioxide from the blood.
Long, narrow openings, mostly in front of the pectoral fins of sharks and rays. Most sharks have five on each side but some more primitive species have six or seven.
Instrument that measures the force of a shark bite. The maximum force recorded as being applied to a single tooth was 60 kg (132 lbs), which converts to a tooth-tip pressure of 3 metric tons per square centi- meter (0.4 inch square). Biting force of an adult human male has been measured at 45 to 68 kg (99 to 142.8 lbs).
Sharks grow slowly, have long pregnancies, and give birth to very few young (pups). Depending on the species, they can take from 3 to 15 years to mature.
Means the vertebral column extends well out into the upper lobe of the fin. In most sharks it is longer and larger than the lower lobe.
Bullhead sharks, see: Bullhead sharks, 1 family: Heterodontidae, 1 genus, 8 species, Heterodont means different teeth, (hetero: different, don’t: teeth) they vary within the same jaw, some are sharp and some are flat for crushing. They possess two dorsal fins, each with a spine at the anterior.
3 families, 3 genera, 5 species. A small group of sharks mainly deep- water bottom dwelling, primitive in form, and resembling extinct, ancient species.
Means that some sharks can maintain their body temperature 10 to 15% higher than the water around them. This is very important be- cause it helps them to move faster while swimming in cold water.
Second oldest known ancient shark. Followed Clasdoselache 320 million years ago, resembling more our modern sharks. Disappeared 65 million years ago to make room for Synechodus.
Scientist who studies fish.
Sharks intestines are not coiled, therefore relatively short and curled, they absorb nutrients easily because the internal spiral valves increase absorptive surface and slow down the passage of digested foods; the short intestines of sharks are very efficient.
A process within the uterus during which embryos derive their nou- rishment by feeding on unfertilized eggs or smaller embryos. See: Ovophagy
International Shark Attack File (ISAF) see: Global Shark Attack File (Shark Research Institute)
The loose attachment of the jaw allows sharks to widen their gape and extend the upper jaw. Sharks do not chew their food because they cannot move the jaw, instead they shake their heads to cut chunks from prey. Jaws are sold as trophies or tourist souvenirs. Help SAVE the sharks and don’t buy them.
Jaws (the movie)
A Hollywood movie that has done more damage to a single group of
animals than anything else in history. The movie was based on the no- vel by Peter Benchley, who later said that he would never have written the novel if he had known then what he knew later in life. The movie caused a shark fishing craze and killing frenzy among fishermen of unequaled proportions; an environmental disaster.
A fleshy or bony ridge along both sides of the tailfin. Those keels are a big help in stabilizing and in minimizing the water pressure while swimming.
7 families, 18 genera, 57 species L. include some large and some rare bizarre forms; they include the Great White shark, cat sharks, thresher, crocodile, mako and porbeagle sharks. Most attain a length of over 4 meter (12 ft), but some, like the crocodile shark, only reach a length of 3 feet.
On or toward the side.
Unlike bony fish sharks have no air bladder. However, their large liver, which can occupy up to 90% of the body cavity, and 25% of the body weight in some sharks, increases their buoyancy. The liver is filled with fatty acids and oils (particularly squalene). The counterbalance of the liver is so effective that a tiger shark weighing 50kg (120 lbs) in the air only weighs 3.5 kg (8 lbs) in the water.
A special method of fishing whereby a line of, in some cases, up to 70 miles long, with thousands of baited hooks attached, is pulled through international oceans. Everything taking the bait is caught and 90% of all animals caught, are thrown back into the sea. Unfortunately most of them are already dead. Sharks get finned and are thrown back into the sea alive. (also see: Bycatch) The most wasteful and brutal kind of fishing and exploitation of the ocean.
The seventeenth-century anatomist who first described the Ampullae di Lorenzini.
Light produced by specialized organs (Photophores). May be used to attract prey or for communication.
Very large Ray, plankton eater.
Swimming with dolphins, seals or sea lions might attract sharks be- cause of the excited reaction of those mammals. Observing the behavi- or of marine mammals may provide a warning. If they suddenly depart it may indicate the presence of large sharks.
Very little is known about the mating of sharks in the wild. Docu- mented reports of reproductive activity are mainly for species held in aquariums. There are many mating variations.
Upper Jaw, not fused to the skull.
Carcharodon megalodon (ancient shark) ancestor of the Great White Shark? Some people say so but it is very unlikely. It was 40 feet long, and lived 60 to 65 million years ago. The largest tooth found was 6 inches long and 4 – 5 million years old.
Metabolism of Sharks
Shark metabolism is closely linked to the oxygen content in the blood.
The crescent-shaped mouth of the shark, located under the snout, can be thrust forward when biting prey. Actually, it is the upper jaw that is thrust forward.
External opening of the nasal organs. Contrary to terrestrial verteb- 92
rates, the nostrils have a purely sensory function and are not associated with breathing.
Sharks have very large livers which contain oil, used by people as a vitamin supplement or in cosmetics.
Organ of Smell. An olfactory bulb is connected to a large olfactory sac concealed inside the nostrils, and from this an olfactory nervous tract extends into the front of the brain.
The bony covering of the gills of bony fishes.
Carpet sharks, Nurse sharks, Whale sharks, 7 families, 14 genera, 31 species. With the exception of the whale shark, most species are bottom dwellers.
Bony fishes, which constitute over 95% of all fish; they only have one gill opening on each side of the head.
A mode of reproduction in which fertilized eggs are laid and hatched outside the female’s body.
Ovophagy (a.k.a. Oophagy)
Intra-uterine cannibalism, a process within the uterus during which
embryos derive their nourishment by feeding on unfertilized eggs or smaller embryos.
A mode of reproduction in which the young hatch from eggs and develop within the female’s body without a placental connection with the mother.
Leeches, trematodes (parasitic latworms), and copepods (tiny crusta- ceans, also known as fish lice), may attach themselves to the body surface, on gills, in the nasal cavity or the mouth of sharks. Round, black copepods (Pandarus satyrus) prefer blue sharks. Another copepod (Dinemoura latifolia) prefers the shortfin Mako as a host. Tapeworms, some very long, and roundworms are often found in the stomach and intestinal tracts of the sharks.
Paired fins, one on each side of the body, which are attached below or behind the gill openings.
Inhabiting the open waters of the ocean.
Located on the undersurface of the body, lying to either side of the cloacal opening.
Never photograph or follow a shark that seems to be swimming in an unusual way.
Luminous organs on the under surface of a sharks body, emitting a greenish light; found in deep-sea dwelling species like the cookie-cutter shark.
Seals and sea lions.
Close to the back, the hind or tail end. In opposition to “anterior” which is close to the front of the body.
A notch on the dorsal or ventral surface just in front of the caudal fin of some sharks. (also see: Keel)
Sawsharks, 1 family, 2 genera and 6 species.
Close relatives of sharks, around 600 species; skeleton made of carti- lage not bone, as is the case with sharks.
The capacity to raise the temperature of only certain body parts.
Remora remora, its dorsal fin is modified into a sucker-like structure on top of the remora’s head. These suckers are used to create a vacuum and allow the remora to cling tightly to sharks and travel the ocean for free. They feed on the parasites like copepods, which attach themselves to the shark’s fins and gills.
Shark reproduction is slow. 40% of sharks lay eggs, 60% have live pups. Most species have 2 to 8 pups once every 2 or 3 years. Hammer- heads can have up to 40 live pups.
Members of the family Carcharhinidae, some are seen as to be dangerous to man, hence the name.
Sharks have between 5 and 7 gill slits. They breathe by taking water in through their mouth and letting it out over the gills where oxygen is absorbed into the blood.
Heat exchanger in the red muscle. Thick-walled arteries surround thin-walled veins. Blood warmed by muscle activity runs toward the heart in the veins, then cool blood carried from the gills by arteries is warmed by heat radiated from the veins. The muscles work more ef- ficiently at the higher temperatures which the rete mirabilis produces.
This is what the British call the spiny dogfish, which they use for “fish’n chips.”
A projecting snout.
Sharks can detect vibrations, movements, sense electric fields and estimate the size of the prey. The Ampullae of Lorenzini, jelly-filled po- res on the front end of the snout, are used for detection of electric and magnetic fields. This is a sense we humans don’t have. Sharks can see, smell, hear, feel, touch, taste, detect vibrations, movements and sense electric fields. A highly sophisticated system.
Many if not most shark-related incidents are better classified as accidents.
Shark Attack Files
Global Shark Attack File (GSAF) The international file created by and for the medical
profession which records all shark accidents worldwide. Members include surgeons, physicians, medical examiners, shark biologists and behaviorists. The GSAF maintains a network of investigators throughout the world. www.sharkattackfile.net
International Shark Attack File (ISAF)
A statistical file which logs shark accidents reported by the media.
Shark Attack Survivors (SAS)
A network of individuals who have been bitten by sharks who offer assistance to each other and maintains a log of reported accidents. SAS works closely with GSAF. www.sharkattacksurvivors.com
Shark Fin Soup
Millions of sharks die a brutal death for this soup. Chop- ping off the shark’s fins, which are essential for its survival, is an extremely brutal practice that needs to be stopped. Finning is driving many shark species into extinction. The average Chinese wedding will cost the lives of 30 to 40 sharks. 70 million sharks die for this soup annually.
UK registered marine conservation charity.
A German conservation group with the objective to pro- tect sharks with a very interesting website: www.sharkproject.org
An international organization to help protect sharks
Shark Research Institute
An international organization, working in many coun- tries which conducts and sponsors research on sharks and advocates shark protection. www.sharks.org
Close relatives of sharks and rays.
The skeleton of sharks is made of cartilage, not bone, therefore it is flexible and very light in weight. The jaws and teeth are strengthened with calcium.
Shark skin is covered with dermal denticles, which are tiny tooth-like structures. Each species has different shapes, which are aligned in a way that they improve hydrodynamic efficiency by braking up the interface between skin and water; thus reducing turbulence while swimming. Historically the skin was used for sword handles and boots. Dried dog- fish skin was used as sand paper, and called “shagreen.” Today, scientists have replicated the drag-reducing qualities of shark skin via an invisi- ble layer of film on everything from airplanes to boat hulls and even swim suits. The film sports what scientists call riblets – modeled after the shark’s dermal denticles – and can diminish drag on airplanes by 8 percent. This technology is outlawed on yachts sailing in the America’s Cup.
Sharks have a superb sense of smell. They can detect a drop of blood or fish extract in concentrations of less than one part per million parts of sea water.
The part of the upper head in front of the eyes.
Think first! Never spearfish where you expect sharks. Blood and the distress movements of speared fish will attract sharks that might want to get the fish from you.
500 species are currently recognized, but there could be more, since new species are discovered each year.
The speed of sharks varies from species to species. For example the whale shark and the basking shark swim a lot slower than the sprint of a shortfin mako, which can accelerate to 22 mph (35 Km/h).
A respiratory opening posterior to the eyes, through which water can be drawn and passed over the gills for sufficient supply of oxygen.
Increases the absorptive surface of the intestine and slows down the passage of food. Another function of the spiral valve is to produce white blood cells.
The order comprises of 7 families, 22 genera and about 51 species of mainly deep water inhabitants. Species includes the large Greenland shark and many small deep-sea species, which possess luminous organs. Many of these species are less than 0.3 meter in length (approximately 1 foot).
Angel sharks, 1 Family Squatinidae, 1 genus Squatina, 10 species, they have a broad flat head and a body with large, wing-like pectoral fins.
The silhouette of a surfer paddling on a surf board could look like an interesting object to a shark. Great Whites and Tiger sharks have taken bites out of surf boards, most likely to taste if it is food. Almost always it was a case of mistaken identity and, though some people have been killed that way, most have been let go after one bite.
The third oldest known ancient shark. They are most likely offspring of the Hybodonts, which are believed to be ancestral to Synechodus and the modern Elasmobranchs.
Tags are used gather information on distribution, numbers, growth and movements of sharks. There are three types of tags used to gather this information: visual ID tags, satellite tags and radio tags. Visual tags are comparatively inexpensive but depend on the shark being seen again or caught. Radio telemetry logs information in a receiver when a tagged shark comes with in range and works well with resident species of sharks. Satellite tags are very expensive but can track the movements of a shark worldwide up to a year, depending on the amount of data they are programmed to gather.
The portion of an animal’s eye that helps enhance night vision; it con- tains reflecting plates, just behind the retina, which are responsible for the reflective blue-green to gold glow seen in the eyes of some animals at night when light shines on them. In sharks, the tapetum lucidum consists of two parts: a series of silvery reflecting plates containing crys- tals of the pigment guanine, and mobile cells, called melanoblasts, con- taining the dark pigment melanin.
Sharks have a fine sense of taste, even though they have the reputati- on of eating anything. Taste buds are present in the upper part of the mouth and are probably responsible for the sharks’ final acceptance or rejection of prey.
Sharks’ teeth are arranged in several rows on both jaws. They are strengthened with calcium and have different shapes in different spe- cies. They can be sharp in the front and flat in the back for crushing crustaceans, triangular with serrated edges, or long and needle-like. Teeth will grow back as needed and the tooth in the second row will move to the front if one tooth is lost. A shark can go through many thousands of teeth during its life-time.
The length of a shark measured from the tip of the snout in a straight line to a point on a line perpendicular to the tip of the upper lobe of the caudal fin.
Toward or on the undersurface of the body.
Any animal with a spinal column.
The visual system of sharks is sophisticated and quite complex in day- light and at night. Most sharks have two types of light receivers called rods and cones, which means they can see black and white as well as color. (See ‘Eyes’ and ‘Tapetum lucidum’).
A mode of reproduction in which the young hatch, develop, and are nourished within the female by a placental attachment. This is com- mon in mammals but unusual in fishes. Occurring in hammerheads, blue sharks, bull sharks, smooth dogfish and mammals.
A garment (usually neoprene) worn by divers to retain body heat and provide protection from abrasions. Always wear a wetsuit when diving near sharks. Research shows that color has no influence on interaction with sharks.