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*MARINE VERTEBRATES These share 3 fundamental characteristics, backbone, which enclose the nerve cord, and bilaterally symmetry and a presence of an endoskeleton.

THE FISH

There are over 22,000 species of fish which make up more than half of all vertebrate species and most (58%) are marine.

 

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*Jawless fish, Agnatha, first appeared about 550 million years ago. They occupied the worlds rivers and seas and lived unchanged for about 100 million years until 2 revolutionary developments occurred, namely biting jaws which developed from the front gill arches and fins became paired.

 

 

 

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*These enabled fish to be able to eat a variety of foods and swim better. The jawless fish population declined after this. Chondrichthyes evolved before bony fish. These cartilaginous fish had a ventral mouth and a skeleton made of cartilage. The bony fish had a true bone skeleton, specialized mouth, and a swim bladder.

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*In 1938, off the coast of South Africa, near the Chalumna River, a fisherman brought up a strange fish. It weighed a hundred pounds and was 4 feet long. The body was covered with circular scales and when it was identified by Prof. JBL Smith, it was found to be a living member of an ancient class of fish that was thought to have gone extinct 70 million years ago.

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*It was the Coelacanth, the oldest true fish.

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*The body forms of the fish are adaptations to the environment or special behavior patterns.

The streamlined or fusiform shaped fish allow rapid movement through the water ad are found in predatory fish.

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Fish compressed from side to side can easily move through plants and in narrow spaces.

Flattened dorso-ventrally, depressed, are usually bottom dwellers.

Attenuated...elongated eels live in sand, mud or under rocks.

 

 

 

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*Fins aid in locomotion. The dorsal and anal fin are used as rudders to prevent rolling, paired pectoral and pelvic fins are used in turning, balancing, and braking. The caudal or tail fin is used mostly for pushing against the water.

 

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*In sharks, and other cartilaginous fish, the fins play a role to stop the fish from sinking because of the lack of an air bladder.

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*Three types of fins are found on the tail, heterocercal, the top is taller than the bottom of the fin, homocercal, both top and bottom of tail are the same... symmetrical, and diphycercal, the tail ends in a point.

 

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*The mouth of a fish and its teeth are adapted for the type of feeding the fish carries out. There are 5 types of feeding methods:

1. predators, specialized teeth for grasping and chewing,

2. nibblers, take small bites,

 

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*3. food strainers, use of gill rakers to strain the food floating in the currents,

4. food suckers, bottom feeders who draw food through the mouth like a vacuum cleaner and

5. parasites, attach to another fish and live off its juices. (Candiru or Vampire Fish)

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*Fish have a one way digestive system. Food enters the mouth and passed to the pharynx where it is funneled to the esophagus. In parrot fish, sucker fish, etc. the pharynx is equipped with teeth that grind, grasp and tear the food before it enters the esophagus.

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*Puffers, globefish, porcupine fish can pump water into their stomachs to inflate themselves.

Parrot fish, pipefish, and seahorses don't have stomachs and digestion and absorption take place in the intestine.

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*Food passes from the stomach to the intestine where chemical digestion continues and the end products are absorbed. The intestine is folded, coiled and spiraled to increase surface area. Meat eaters have shorter intestines than plant eaters. Nutrients absorbed enter the blood and are transported to various parts of the fish by the circulatory system.

 

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*Circulation

Blood is pumped from the heart to gills where gas exchange takes place. Blood carries oxygen via red blood cells to all parts of the body, transports CO2, digested food, wastes etc. and returns to the two chambered heart. The heart has one atria and one ventricle

 

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*Respiration

Most fish obtain oxygen directly from seawater using a gill. Water is taken in through the mouth and pumped over the gills. The gill is located behind the mouth in the gill chamber and consists of several gill arches. Each gill arch supports many gill rakers and gill filaments.

 

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* Dissolved O2 diffuses across the thin membranes of the gill and enters the blood. The gill rakers are positioned to stop particles suspended in water from damaging the filaments. Water pumped past the gill leaves the gill chamber through the gill slit. The gill slits in bony fish are covered with an operculum.

 

 

 

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*Jawless and cartilaginous fish have open gill slits. Sharks and rays have a modified gill slit, the spiracle which works with the mouth to bring water into the gill chambers. It is found on the dorsal surface of rays.

 

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*Gas Exchange

Thin membranes of gill filaments make gas exchange easy. Diffusion occurs and O2 is picked up by the blood. Diffusion is increased by two features,

1.-surface of gill filaments increased by branching increasing area of membranes which come in contact with water and

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*2.-water flowing over gills move in opposite direction of blood movement in the gills. This counter current system enables blood to pick up a maximum amount of O2 from the surrounding water. Adaptations include: carp gulping air which can diffuse into the gill filaments, lungfish with air sacs, enlargements of the gill chamber etc.

 

 



 

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*Buoyancy

Fish with well-developed swim bladders can remain poised at a desired level with minimum effort by increasing or decreasing the amount of gas in the bladder. The bladder can be filled by gulping air or release of gas from the blood through gas glands.

 

 

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*When the fish goes deeper, the increased pressure squeezes gas in the bladder, decreasing gas volume of the bladder. The fish becomes heavier/denser.

The fish restores gas volume by secreting gas from the blood. As the fish moves up, there is less pressure on the bladder, and the gas expands.

 

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*The fish becomes lighter and more buoyant so in order to prevent the bladder from overfilling, the fish must reabsorb the gas. Fish with an air-tube connecting the bladder to the digestive tract can let gas escape through the mouth, (open swim bladder) but a closed swim bladder system, reabsorption is necessary.

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* If a fish was pulled up from deep water quickly, its swim bladder could explode! Vertical movement is limited by the swim bladder...predators like sharks, don't have to worry about that because they have no swim bladder.

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*Temperature

Temperature has a profound effect on metabolism of fish because most are cold-blooded (ectothermic). Generally a rise in temperature speeds up the metabolism and a drop slows down metabolism and reduces swimming speed etc.

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*Most fish generate heat but lose it rapidly to the surroundings because they lack insulation. Predatory fish have evolved a countercurrent system for conserving heat and muscles can stay warm with energy producing reactions.

 

 

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*Excretion.....Disposal of wastes produced during metabolism

Bony fish have salt secreting cells in the gills called chloride cells that remove excess salt.

 

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*Sight

Like the human eye in some ways but the density difference between the water and cornea of the eye is not so great so the lens of the fish is hard, dense and round to maximize refraction. Light is focused by moving away or toward the retina.

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*The eyes bulge out with the lens protruding through the pupil. Iris is not adjustable. Color vision is developed in fish mainly in shallow clear water helping locate food, breeding partners and avoiding predators. The eyes are on either side of the head increasing the visual field which helps for animals with no neck!

 

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*Hearing and Balance

Ears, lateral line organs and swim bladders aid in detecting underwater sounds, maintaining balance and enabling some fish to produce sounds. The inner ear, labyrinth, functions for hearing and balance. Fluid filled canals and receptor cells, neuromast sense cells are sensitive to movement in fish.

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*It bends and pushes ciliary hairs of the neuromast sense cells and the impulse is sent to the auditory nerve to the brain. Ear stones, otoliths, move in the tubes in conjunction with fish movements, shifting positions,and this helps with the balance and hearing.

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*The neuromast cells are also found in the lateral line organ, detecting low frequency vibrations. The swim bladder vibrates as sounds in water pass through the fish. These vibrations are passed to the inner ear. The toad fish generates sounds in this way.

 

 

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*Smell...chemoreception

Detection of dissolved substances in water is how the fish can smell its food. Taste buds in the mouth taste the food, barbels, whisker-like appendages, contain taste buds which enable the fish to probe muddy waters

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*Electroperception

The ability of fish to detect weak electrical currents in water/or generate them. This is used for communication and examining the environment. Some can discharge several hundred volts, stunning its prey and easily capturing them to eat.

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*Cartilaginous fish have sense organs in the head called the ampullae of Lorenzini that can detect weak electrical fields. It is used to help locate their prey, assist in navigation and maybe even detect currents.

 

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*Outer Covering

The entire skin of the fish is alive, even the scales are covered by a thin layer of living cells, the epidermis the only protective material covering the epidermis is slime secreted by mucus glands scattered over the body

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*The mucus reduces friction and protects against bacteria etc. Fish odor or body odor is found in the slimy covering. This allows fish to recognize their species.

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Scales form a protective outer covering. There are 4 types of fish scales. Sharks and their cartilaginous relatives possess tooth-like Placoid scales.

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*Platelike Ganoid scales made of bone are found on primitive fish like the gar pike and sturgeon.

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Cycloid and Ctenoid scales form an overlapping covering like roof shingles on a house. The scales are thin and flexible allowing great mobility. Cycloid scales are mainly found on soft-ray fish and ctenoid scales are mostly found on spiny ray fish.

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*Coloration

This serves in functions like camouflage, looking for a mate, advertising the fact its poisonous or showing willingness to remove parasites. Two types of cells control color namely Chromatophores and Iridocytes.

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*Chromatophores are starshaped pigment cells located under transparent scales or in the thin cell layer overlying the scales. The nervous system and endocrine system seem to control the redistribution of pigments within the chromatophore. Iridocytes are pigment cells containing reflecting granules (work like mirrors).

 

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*The silvery stripes and iridescence of some fish result from light being reflected by iridocytes. There is warning coloration, cryptic coloration (blend), disruptive coloration, and countershading.

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*Defense and Migration

Fish that don't swim well have evolved protective devices. Some include the sharp spines of the surgeon fish and trigger fish or the protective armor of the trunk fish, seahorse and pipefish. Seahorses have a prehensile tail which they use to hold on to underwater branches and remain motionless

 

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*Globefish and puffers expand their bodies by pumping water into their stomachs. Coloration...countershading is where the dorsal side is darker than the ventral side making the fish difficult to see. The clownfish has contrasting colors to deceive the predator (disruptive contrast).

 

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*Secretions...unicorn fish expels a cloud of ink, and stonefish and scorpion fish possess poison glands.

Schooling fish apparently have a decided advantage over non-schooling fish.

 

 

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*Migration

There are two reasons for seasonal migration. 1. food and 2.breeding. Migratory fish travel thousands of miles to return to the same place each year. If they breed in fresh water they are anadromous and if they breed in salt water they are catadromous.

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*A third type remain in the ocean and move on definite pathways between feeding and breeding areas. The ocean wanderings of migratory fish correspond to ocean currents

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*Reproduction and life history

Many ways have evolved for marine fish to reproduce.The sexes are usually separate and both sexes have paired gonads located in the body cavity. In most marine fish, the gonads produce gametes only during certain periods of time. This is crucial because both sexes need to be ready at the same time...especially in those that migrate to breed.

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*The timing is controlled by sex hormones which are released into the blood to stimulate the production of gametes. They are released by being triggered by environmental factors like temperature, light, and food availability.

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*Some fish are hermaphrodites and though able to fertilize themselves they usually breed with other individuals to ensure fertilization between species. This is also common in deep water fish as an adaptation to the dark depths and the chance of NOT finding another fish of the opposite sex.

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*Sex reversal also occurs in some fish. Individuals begin life as males but eventually change into female or vice versa.

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*Fertilization in fish is usually external but in some cases, internal fertilization happens. Different types of development of the egg occurs. Usually external fertilization involves the production of many, I mean many, eggs. They end up floating in the plankton and most don't survive. This is OVIPAROUS, or the egg develops outside the body and feeds off the yolk

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*Some fish, mainly cartilaginous ones, have eggs that develop inside the body and the young are born alive. This is OVOVIVIPAROUS. Some rock fish have this method of reproduction.

In some sharks and rays, the embryos actually feed off nutrients of the mother. This is like mammals and is known as VIVIPAROUS.

 

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Lampreys.. eel-like and has one or two dorsal fins a caudal fin and no paired fins. The mouth, jawless, is a disk adapted for sucking, with a complex arrangement of teeth, their arrangement specific to the species and therefore used in classification (Agnatha-2 classes, 1 order each, Lampreys have 3 families with a total of 72 species

 

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*Hag fish or slime eels are eel like have a fleshy fin, and flattened caudal region. They have 4 to 6 tentacles around the mouth. No jaws or stomach but are parasites of larger fish and defend themselves by releasing slime

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*Sturgeons are the largest and longest lived freshwater fish and provide food! Caviar! The sturgeon and paddle fish are the only survivors of an ancient group of fish. They migrate to and from the sea.Sizes are impressive...1800lbs,

Bowfin and Garfish...bowfin can survive out of water using their air bladder as a lung.

 

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* Garfish, long bodied predators long jaws and many teeth and armor like scales.

Tarpons, Eels, Notacanths...weird that these unalike fish are grouped together but all have larva unlike the adult.

 

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*Bristlemouths...luminous organs, bristle like teeth eyes on stalks

Lizard fish and Lantern fish...sit on pelvic fin and lower tail lobe

Spiny finned fish latest flowering of bony fish evolution.

 

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*Billfish

The term billfish encompasses two closely related families, the Istiophoridae: sailfish, spearfish, and marlins and the Xiphiidae, the swordfish.

 

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*The term billfish is usually reserved for the istiophorids and call the only member of the family Xiphiidae, a swordfish. Both families of fish have members whose upper jaw is extremely elongated and narrow. These are all fast-swimming, aggressive fish in the open ocean with a tall dorsal fin and lunate (quarter moon shaped) tail.

 

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*They have a unique circulatory system that keeps the warmth generated by their active swimming retained in the muscles. This makes their muscles slightly warmer than the surrounding water and gives them an advantage over the slower-moving, completely cold-blooded fishes.

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*Most are tropical and subtropical in distribution but are often caught in temperate waters, especially in summer months.

They are among the oceans fastest swimmers. Sailfish have been clocked at a minimum of 70 MPH for short bursts and probably cruise at 20 to 30 MPH. The long bill is thought to be a cutwater which aids these fish in very fast swimming.

 

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*It is also used to decimate schools of fish by thrashing it back and forth horizontally through the water and is thought to be used in "battles" with other bill fish. The lunate tail and narrow, keeled peduncle (area just before the tail) are also adaptations for fast swimming.

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*Even the dorsal and pelvic fins of the sailfish fit into neat grooves on the body to prevent any unwanted drag. Although marlin may be somewhat slower than sailfish, and swordfish slower yet, "slower" in this case is still close to 40-50 MPH.

 

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*There are eleven species of billfishes and swordfish, five of which are found in the Gulf of Mexico. The term includes two fish families, which inhabit tropical and sub-tropical oceans worldwide.

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*The family Istiophoridae contains ten members: the marlins (genus Makaira), the spear fishes and white marlins (genus Tetrapturus), and the sailfishes (genus Istiophorus). The swordfish, Xiphias gladius, is the only member of the family Xiphiidae.

 

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*Swordfish can easily be distinguished from the istiophorids. The sword or bill of the swordfish is a broad flat blade making up about one-third of the body length. In addition, the fish lacks pelvic fins, and in the adult, teeth and scales.

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*Although all billfish are large, (at least 5 feet), the two edible species outdo themselves. Both marlins and swordfish are taken at lengths of 6 to 15 feet and 300 lbs to 1000 lbs.

 

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*They undergo long distance migrations and range far afield for their food. One fish, tagged off the Virgin Islands, was caught four months later 4,500 miles away off the coast of West Africa.

 

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Young fish less than an inch in length, may take refuge from predators under floating Sargassum or sea grass. Here they prey on smaller, less active fish who are also seeking safe harbor

Adult billfish eat a wide variety of fish: flying fish, scad, mullet, round herring, ballyhoo, mackerel, tuna, and jacks.

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*They also eat squids and other billfish. Only humans and mackerel sharks, killer whales and bigger billfish eat billfish.

The bill can be used in aggressive encounters with other billfish as evidence of billfish caught with pieces of bill embedded in their bodies. Whales have also been attacked by billfish.

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*Catch them on hook and line, baited with live mullet, mackerel or squid though the numbers are dropping rapidly.

Large marlin are always females. Whether males change sex as they attain greater size and become females or just stop growing as fast as the females is presently being studied. Small specimens of males and females are found its just only females are the record catches!

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*Sharks.

Over 350 million yrs ago, something new happened in the primeval seas...an entirely new class of vertebrates evolved which were quite different from anything before. They had tiny tooth-like body armor called placoid scales, exposed strap-like gill openings, unique paired copulatory organs and flexible skeletons of cartilage

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*These groups settled on a lifestyle that has persisted to the present. They are slow growing, late maturing, produce small numbers of well formed young of whom a mother invests a lot of resources during development but virtually nothing after the young are born.

 

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*Most people think sharks are large, fast swimming elegant savage predators. This is true of some species but only a minority. The group should be of general interest because of the intriguing aspects of biology found in sharks, the exceptional sense of smell, electropreception, and giving birth to live young.

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**One notable feature is its teeth. In the highly predaceous sharks, these are large and razor sharp used for cutting and shredding their prey into bite size pieces. Some however are bottom feeding species and eat mollusks and crustaceans and their teeth are flattened for crushing the shells of their prey. The fish eaters have long thin teeth to help catch and hold their prey..

 

 

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*A shark may have up to 3000 teeth arranged in 6 to 20 rows according to the species. In most sharks only the first row or two are actively used for feeding. The remaining rows are used for holding prey. They are in various stages of formation with the newest at the back.

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*As a tooth in the functioning row breaks or is worn down, it falls out and a replacement tooth moves forward in a sort of conveyor belt system. They can be replaced every few days. This keeps the functional row sharp. The shark may use over 20,000 teeth in a lifetime and the strength of the jaws can exert a biting strength of 3000kg per sq. cm. (44000 lb/sq. in. on the teeth. (humans are 150lbs).

 

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*Sharks find their prey through a number of sensory systems. Many have poor eyesight but some are real good. Some have barbels around their mouth to taste the sea bed for prey. All sharks have a very keen sense of smell. Their nostrils are used only for smelling, not for breathing. The part of the sharks brain that deals with smelling is twice as large as the rest of the brain.

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*Sharks can detect 1 part of blood per million parts of seawater (1 drop in 25 gal). They have a lateral line system which is a series of canals on the entire body and head which are filled with a jelly-like substance, which are sensory receptors which pick up pressure waves caused by movements of other animals or even by the shark itself.

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*On the snout are ampullae of Lorenzini, a series of electro-receptive pits which are the most sensitive electro-perceptive devices found in any animal. They are capable of picking up one-millionth of a volt, which is less than the electric charge produced by nerves in an animals body. The sharks can find their prey from the prey's natural electric output.

 

 

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*Sharks..The six and seven gilled sharks have extra sets of gills preferring cold water some being filmed at 1800m. The orectoloboids are five closely related families of sharks ranging from 3'long to the whale shark 50' long.

 

 

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*All but the whale shark are bottom dwellers and spend most of their time just sitting on the ocean floor and actually skeletons modified so they can actually use their fins for walking on the ocean floor. They have sensory barbels around their mouth

 

 

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*The whale shark has gill arches specially modified to act like a sieve to filter out the planktonic organisms upon which it feeds. Because it of its bulk it needs constant fuel and feeds as it swims.

 

 

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*The thresher, mackerel are among the largest group of sharks in the world. They have a long upper lobe on their caudal fin and use it by swimming through a school of small fish, thrashing the tail and killing or stunning the fish which are then eaten.

 

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*The family of mackerel sharks include the great white, mako and basking sharks. Their caudal fins have lobes being nearly equal in length. Most if not all are homothermic which means they can keep their body temperature above that of their surroundings. The Mako is probably the fastest, measured at 60mph and is known to have out swum and eaten swordfish.

 

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*The great white/white death/white pointer etc. mainly feeds on marine mammals, the only shark to do so, and has broad serrated teeth designed for biting large chunk of flesh from whales and seals. It is viviparous, meaning the embryos develop in the uterus. The basking shark is another filter feeder and the second largest in size...45'.

 

 

 

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*The requiem sharks, are the typical sharks, the bull shark, which can enter freshwater and has been found more than a thousand miles from the mouth of large rivers. The largest is the Tiger shark..18' and the most dangerous. It swallows almost anything, including roles of tar paper, shoes, gas cans, license plates, cans of paint and human parts

 

 

 

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*Hammerhead sharks, also in this group, have large lateral expansions of their head on which the eyes are set. They grow to 15' and the expanse of the head gives a better field of vision, and a more expansive electro-detecting system.

 

 

 

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*Shark Reproduction

Success is due to the reproductive adaptations. Males have claspers which release sperm into the cloaca. Young are born as miniatures of the adults and few in number. Their large size reduces predators and allow for more nutrients for the young. Eggs are produced with large yolks.

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*3 types of egg laying:

1. ovipariy- egg laying...bull head, some nurse sharks

2. ovovivipary- thin shelled eggs hatching in the uterus before full development. No placental development, use yolk. Tiger, dogfish.

3. Vivipary-no shells-some yolk but mostly nourished by mother through the placenta. Bull, lemon, hammerhead, great white.

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*Skates Rays and Chimaeras.

Examples are the eagle rays, electric rays, guitar fish, mantas, sawfish, skates, stingrays, and the chimaeras. There are about 300 species of rays and skates which have flattened bodies and live usually on the bottom (Demersal).

 

 

 

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*There are some rays that look like sharks and some sharks with flattened bodies so the way to tell is that the skates and rays all have heir gill slits on the ventral surface. The enlarged pectoral fins are fused to the head and the eyes are on top of the head.

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*The stingrays have a whiplike tail usually equipped with spines for defense. Poison glands produce venom. Skates are like rays but lack a whiplike tail and stinging spines. Some can have electric organs .

Rat Fish ..about 25 species of this deep water chimaera, is separated because the gill slits are covered by a flap of skin. The long tail gives it the name "ratfish".

 

 

 

 

 

 

 

 

 

     A modern Tarpon fishing method that has surfaced recently is to sight fish these creatures which can be really rewarding.  Tarpon can be found rolling and feeding on the surface throughout Charlotte Harbor. Live bait and artificial are the weapons of choice here. These fish are feeding in 5-15 foot of water and when hooked on the end of your line become explosive. Tackle is 25-30lb gear with 100lb leader and 7/0 hook for live bait or a variety of plugs and/or flies for the Fly-Guys.

 

     There are no crowds to contend with and if there is another boat in the area he's probably your buddy. This gives you the room for unforgettable action allowing ample space and time to fight even the biggest of Tarpon. On a typical day you can easily jump 10 Tarpon fishing, and perhaps boat 2 or 3. But one thing for sure it beats fighting a crowd and makes a trip a lot more memorable, And the scenery in Charlotte Harbor is magnificent.