*MARINE VERTEBRATES These share 3
fundamental characteristics, backbone, which enclose the nerve cord, and
bilaterally symmetry and a presence of an endoskeleton.
There are over
22,000 species of fish which make up more than half of all vertebrate species
and most (58%) are marine.
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.
*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.
*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.
was the Coelacanth, the oldest true fish.
forms of the fish are adaptations to the environment or special behavior
streamlined or fusiform shaped fish allow rapid movement through the water ad
are found in predatory fish.
•Fish compressed from side
to side can easily move through plants and in narrow spaces.
•Flattened dorso-ventrally, depressed, are usually bottom
Attenuated...elongated eels live in sand,
mud or under rocks.
*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.
and other cartilaginous fish, the fins play a role to stop the fish from
sinking because of the lack of an air bladder.
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.
*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,
take small bites,
*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
attach to another fish and live off its juices.
(Candiru or Vampire Fish)
*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
globefish, porcupine fish can pump water into their stomachs to inflate
Parrot fish, pipefish, and seahorses don't
have stomachs and digestion and absorption take place in the intestine.
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.
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
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.
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.
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.
membranes of gill filaments make gas exchange easy. Diffusion occurs and O2 is
picked up by the blood. Diffusion is increased by two features,
gill filaments increased by branching increasing area of membranes which come
in contact with water and
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.
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
*When the fish
goes deeper, the increased pressure squeezes gas in the bladder, decreasing gas
volume of the bladder. The fish becomes heavier/denser.
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.
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.
* 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.
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.
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.
of wastes produced during metabolism
have salt secreting cells in the gills called chloride cells that remove excess
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.
*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!
*Hearing and Balance
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.
*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.
*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
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
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.
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.
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
*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.
Scales form a
protective outer covering. There are 4 types of fish scales. Sharks and their
cartilaginous relatives possess tooth-like Placoid scales.
scales made of bone are found on primitive fish like the gar pike and sturgeon.
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.
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.
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).
stripes and iridescence of some fish result from light being reflected by
iridocytes. There is warning coloration, cryptic coloration (blend), disruptive
coloration, and countershading.
*Defense and Migration
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
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).
fish expels a cloud of ink, and stonefish and scorpion fish possess poison
fish apparently have a decided advantage over non-schooling fish.
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
*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
*Reproduction and life
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.
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.
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.
also occurs in some fish. Individuals begin life as males but eventually change
into female or vice versa.
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
*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
sharks and rays, the embryos actually feed off nutrients of the mother. This is
like mammals and is known as VIVIPAROUS.
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
*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
*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.
* 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.
organs, bristle like teeth eyes on stalks
Lizard fish and Lantern fish...sit on
pelvic fin and lower tail lobe
fish latest flowering of bony fish evolution.
billfish encompasses two closely related families, the Istiophoridae: sailfish,
spearfish, and marlins and the Xiphiidae, the swordfish.
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.
*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.
*Most are tropical and
subtropical in distribution but are often caught in temperate waters,
especially in summer months.
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.
*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.
*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
*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.
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
*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.
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
*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.
•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
•Adult billfish eat a wide variety of fish: flying fish, scad,
mullet, round herring, ballyhoo, mackerel, tuna, and jacks.
*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.
*Catch them on hook and line, baited with
live mullet, mackerel or squid though the numbers are dropping rapidly.
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!
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
*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
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.
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..
*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.
*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).
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.
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.
*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.
*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.
*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
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.
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.
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.
*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
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
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.
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.
*3 types of egg laying:
1. ovipariy- egg laying...bull head, some
2. ovovivipary- thin shelled eggs
hatching in the uterus before full development. No placental development, use
yolk. Tiger, dogfish.
Vivipary-no shells-some yolk but mostly nourished by mother through the
placenta. Bull, lemon, hammerhead, great white.
*Skates Rays and Chimaeras.
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
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.
*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
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".
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