Transcript Marine Fish - Science with Ms. Reathaford!

Marine Fish: An Introduction
 Fish were the first vertebrate, appearing more than 500
million years ago.
 The first fish are thought to have evolved from an
invertebrate chordate not much different from lancelets
that still inhabit the ocean.
 Fish soon made their presence felt and have had quite an
impact on the marine environment, feeding on nearly all
types of marine organisms.
 Fishes are also the most economically important marine
organisms.
Economical Importance of Marine Fish
As noted, fishes are the most
economically important
marine organisms because
of the following:
 They are a vital source of
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protein for millions of
people
They are sometimes
ground up for fertilizer or
chicken feed
Leather, glue, vitamins,
and other products are
obtained from them
Sportfishing
Kept as pets by many
An Introduction to Vertebrates
Vertebrate are different from
invertebrate in that they have a
backbone (or vertebral column /
spine) which is a dorsal row of hollow
skeletal elements called vertebrae.
Vertebrae are typically made of bone.
Vertebrae used to enclose and protect a
nerve cord (spinal cord), which ends
at a complex brain. The brain is
protected by the skull, which is made
of cartilage or bone.
Vertebrates are characterized by a
bilaterally symmetrical body and the
presence of an endoskeleton.
Types of Fish
Fishes are the oldest and structurally the simplest of all living
vertebrates. Fish are also the most abundant vertebrates in terms of
both species and individuals.
There are approximately 30,000 species of fish known to science,
making up about half of all species of vertebrates on Earth. Most
known species of fish are marine and many new species are being
added every year.
There is disagreement, among scientists, regarding how to classify
major groups of fish. Despite this, three groups are traditionally
recognized:
1.
2.
3.
Jawless Fishes
Cartilaginous Fishes
Bony Fishes
Jawless Fish: Agnatha
The most primitive fishes living today are the jawless
fishes.
Characteristics:
 Feed by suction with the aid of a round, muscular mouth
 Rows of teeth within mouth
 Body is cylindrical and elongated
 Lack paired fins and scales of most fish
 Lack a true vertebrae, so some scientists argue if they are
truly in vertebrates group
Hagfishes (Slime Eels)
Characteristics:
 Jawless fishes that feed mostly
on dead or dying fish
 Sometimes bore into their prey
and eat them from the inside
out
 Live in burrows they dig in
muddy waters, at moderate
depths in cold water
 Only about 20 known species
 Reach a maximum length of
2.6ft
 Skin is used to manufacture
leather goods
 Known for attacking bait on
fishing lines, nets, and traps
Lampreys
Characteristics:
 Found in most temperate regions,
anadromous fishes (live in
oceans most of their life, move to
freshwater to spawn)
 Uses teeth to create a wound on its
prey, then uses tongue to rasp a
hole in its victim
 Then attaches itself to other
fishes, using buccal papilla to form
a suction, and sucks their blood. It
can also use the buccal tunnal to
wiggle up rock faces
 To prevent the blood from
clotting, lampreys release their
own anticoagulant
 30 known species
External Features: Lampreys
 The skin of a lamprey is
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smooth and slimy, lacking
scales
It has a symmetrical caudal
fin that is tapered at the
posterior end
While it swims, the anterior
and posterior dorsal fins
keep it upright
Lampreys do have muscle
segments (myomeres) that
can be seen through the skin
Excretory waste passes
through the cloacal aperture
Head Features: Lampreys
 There are 7 external gill slits in a
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lamprey, and it uses muscle
contractions to draw in (relaxation) and
expel (contraction) water into the gill
pouches when it is attached to its prey
The primary function of the gills;
however, is to absorb oxygen and
remove carbon dioxide from the blood
The head contains a nostril, which is
not connected to either its mouth or
pharynx
Lampreys are capable of detecting light
due to having a pineal organ
The lampreys brain has olfactory and
optic lobes, which are the most
developed parts
Internal Features: Lampreys
 The main component of the lamprey
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skeleton is the notochord, which runs
along the dorsal length of the body
The heart of a lamprey contains
ventricles, which pump blood through
the gills and the body. Blood then
enters the sinus venosus and then into
the atrium, which pumps blood into
the ventricles
Surrounding the heart is the
pericardial sac, protecting it
Lampreys do not have stomachs as
their diet is liquid (blood), but there is
a liver to store products of digestion
A lamprey does have kidneys, which
remove nitrogenous waste and
balances water
Ancient group of fishes that includes sharks, rays,
skates, and ratfishes.
Cartilaginous Fish: Chondrichthyes
Characteristics:
 Skeleton made of cartilage, which is lighter and more
flexible than bone
 More advanced than jawless fishes
 Movable jaws that are usually filled with well-developed
teeth
 Mouth is almost always ventral (under the head)
 Paired lateral fins for efficient swimming
 Rough, sand-paper like skin due to teeth-like placoid
scales consisting of a pointed tip that is directed
backward
Sharks
Sharks are adapted for fast swimming and predatory
feeding and are one of the most fascinating animals within
the sea.
Because many of them are similar to species that swam in
our seas over 100 million years ago, sharks are sometimes
referred to as “living fossils.”
Shark: External Features
 Spindle-shaped bodies tapering
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from the rounded middle to each
end allows them to move easily
through the water
Caudal fin (tail) is well developed
and powerful and is usually
heterocercal (upper lobe is longer
than lower lobe) which causes the
shark to be driven downward as it
swims
Upper surface of the body features
two dorsal fins, first is longer and
triangular, with a large spine at both
anterior ends
Paired pectoral fins are large and
pointed in most species
Five to 7 gill slits are behind the head
and present on each side of the body
Shark: Head Features
 Shape of head provides lift to compensate for
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downward thrust of caudal fin when swimming
Powerful jaws have rows of numerous sharp,
often triangular teeth that are embedded in a
tough, fibrous membrane that covers the jaws
Lost or broken teeth are replaced by another
that slowly shifts forward from the row behind
it as if on a conveyor belt
Has an inner ear, which senses sound and helps
maintain balance
Contains spiracles, which bring water into the
gills when the mouth is closed
Complexity allows sharks to see in color
Sharks are efficient hunters because their
nostrils allow them to dinstinguish which side
is closest to the strongest scent (swims in that
direction)
5 pair of external gill slits in most species
Shark: Internal Features
 Possesses an oily liver, which helps with buoyancy for the
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shark
Bile is stored in the gallbladder, which helps break down fat in
the sharks diet
Also has a spleen, which produces red blood cells
Intestines house the spiral valve, which increases the surface
area of the intestine for larger feedings
The sharks stomach contains many wrinkles (rugae)
Heart allows blood flow to enter sinus venosus and then to
atrium where it is pumped into the ventricles, which pump
the blood to the gills and then to the body
Salt is removed from the sharks body through a rectal gland
Exceptions
There are nearly 350 living species of sharks, but not all
conform to the typical body plan:
 Hammerhead Sharks: flattened heads with eyes and
nostrils at the tip of bizarre lateral extensions. The head
serves as a sort of rudder ad separates the eyes and nostrils
to improve the sharks sensory perception.
 Sawsharks : extends in a long, flat dorsoventrally flattened
blade armed with teeth along the edges.
 Thresher Sharks: upper lobe of the tail is very long, which
they use to herd and stun schooling fishes when they eat
Exceptions in Size
The size of a fully grown adult shark also varies:
 Spined Pygmy Shark: grows to no longer than 10in
 Whale Shark: largest of all fishes found in tropical waters
around the world, may be as long as 60ft but any species
longer than 40ft are rare. Despite this, they cause no harm
to humans and are filter feeders
 Basking Shark: 50ft on some occasions, but most do not
exceed 33ft. Basking sharks are also filter feeders
 Great White Shark: considered most dangerous shark of all,
exceeding 20ft in length
Shark Habitats
Sharks are found throughout the
oceans at practically all depths,
but they are more prevalent in
tropical coastal waters.
Sharks are primarily marine, but
a few species travel far up
rivers. Small specimens are
typically found in brackish
waters, in estuaries, and
coastal regions.
 Bull Sharks
 Northern River Sharks
 Speartooth Sharks
Overfishing of Sharks
Due to our appetite for shark, overfishing has become a great problem.
Common Reasons of Shark Fishing:
 Shark meat is eaten around the world, many people eat it without knowing, as it is often
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illegally sold as “fish” or “scallops”
Sharks are fished for their liver oil
Sharks are fished for their skin, which is processed into leather or sandpaper
Sharks are fished for their fins – Shark Fin Soup is a delicacy in the Orient
Shark cartilage is a “joint nutrient” that may help in use of arthritis
Overfishing of sharks has led to more stringent management of shark fishing. The
number of sharks is declining across the world due to slow-growing and slowreproducing of the animal.
There has also been a ban placed on shark finning in the USA and other countries
around the world.
Web MD: Shark Liver Oil
Overview and
Information
Shark liver oil is used to
make medicine. It is taken
from the livers of three
species of shark: the deep
sea shark, the dogfish
shark, and the basking
shark
The liver makes up about
25% of the total body
weight of these sharks
Common Uses
•to treat leukemia and
other cancers
•to prevent radiation illness
from cancer X-ray therapy
to prevent the common
cold, flu, and swine flu
•to boost the body’s
immune system
•To increase white cell
counts during treatment
with anti-cancer drugs
(chemotherapy)
•To treat skin conditions,
including skin cancer
How it Works
Shark liver oil contains
chemicals that might have
activity against cancer or
cancer treatment related
side effects
Rays and Skates
There are 450-550 species of rays and skates in the marine world.
Characteristics:
 Dorsoventrally flattened bodies
 Demersal (live on bottom of ocean, for most part)
 Gill slits (5 pairs) are on the underside of the body rather than on
sides
 Pectoral fins are flat and expanded, like wings, and are fused with
the head
 Eyes are on top of the head
Exceptions:
Not all rays are demersal. Eagle rays, the manta, and devil rays “fly”
through water using ther pectoral fins like wings. Each of these have
been observed leaping out of the water
Tropical Sawfish
Characteristics:
 Look like sawsharks but have
ventral gill slits (so grouped
with rays)
 Feed by swimming through
schools of fish and swinging
blades back and forth to disable
prey
 Known to grow up to 36ft long
Stingrays
Characteristics:
 Whip-like tail equipped with stinging
spines at the base for defense
 Poison glands produce venom causing
wounds to anyone who steps on them
 Many abdominal wounds result in death
to those handling them
 Cover themselves completely with sand,
nearly invisible
 Feed on clams, crabs, small fishes, and
other animals in sediment
 Lift sediment with fins to expose prey
and then crush them with teeth
modified into grinding plates
 Give birth to live young
Electric Rays and Skates
Electric Rays
Characteristics:
 Possess special organs that
produce electricity on each side
of their head
 Deliver shocks to prey of up to
200 volts
 Ancient Greeks and Romans
once used electric rays to cure
headaches and other ailments…
the original “shock treatment!”
Skates
Characteristics:
 Similar to rays in appearance
and feeding habits
 Lack a whip-like tail and
stinging spines
 Some have electric organs
 Lay egg cases
 Abundant, are fished for food
in some parts of the world
Bullseye
Electric Ray
Skate
Ratfishes
About 30 species of ratfishes are
grouped separately due to their
unique characteristics:
Strange looking, mostly
deep-water
Have only one pair of gill
slits, covered by a flap of
skin
Long rat-like tails
Feed on bottom dwelling
crustaceans and molluscs
The great majority of fishes are bony fishes. As the name implies,
they have a skeleton made at least partially of bone.
There are approximately 23,000 species of bony fishes – about
96% of all fishes and almost half of all vertebrates – with 75-100
new species being named every year.
A little more than half of all bony fishes live in the ocean, where
they are the dominant vertebrates.
All land vertebrates are said to have evolved from early bony
fishes.
Bony Fishes: Osteichthyes
Characteristics:
 The composition of the skeleton is not the only distinguishing
feature of bony fishes
 Usually have cycloid or ctenoid scales (thin, flexible, and
overlapping).
 Cycloid scales are smooth
 Ctenoid scales have many tiny spines along exposed borders
 Scales are made of bone and covered by a thin layer of skin
and protective mucus layer
 Scales have growth rings, in which you can count to determine
the age of the fish
 Some bony fishes lack scales altogether
 Operculum (gill cover) that protects gills and helps pump
water over gills while fish is stationary
Bony Fishes: Fins
Characteristics:
 Upper and lower lobes of the
tail (caudal fin) are the same
size (homocercal)
 Fins consist of thin membranes
supported by bony spines (fin
rays) that are used for
protection
 Some fin rays are flexible and
used for propulsion and
manuevering
 Fin rays help a fish “hover” in
one location
 Dorsal fins help the fish remain
upright in the water while
swimming
Bony Fishes: Head
Characteristics:
 Bony fish have large eyes, with large
pupils, that help it see in dim
underwater environments
 Nostril openings lead to nasal cavities
 Terminal mouth (located at anterior
end)
 Jaws with much more freedom and
movement than other groups of fish
 Protrusible jaw (can be projected
outward from the mouth) with
attached teeth on both jaws
 Teeth are replaced, but do not move
forward as other groups of fish
 Bony fish often swallow their food
whole, although they have teeth
Bony Fishes: Internal Structure
Characteristics:
 Presence of a swim bladder (gas-filled sac) just
above the stomach and intestines to provide
bouyancy
 Swim bladder compensates for heavy bony skeleton
 Oviparous (eggs are fertilized and develop
externally)
 Ovoviviparous (fertilized internally and young are
live at birth
 Liver to regulate glucose levels in blood
 Stomach divided into two parts: cardiac and
pyloric
 Food moves from stomach to intestines through the
pylorus
 Spleen to produce white blood cells
 Pancreas to produce enzymes to help digestion and
produce insulin
 Kidneys function based on habitat: freshwater –
remove excess water / saltwater – conserve water
Bony Fishes: Habitat
Bony fishes are extraordinarily diverse in shape, size, color,
feeding habits, reproductive patterns, and behavior. Due
to this, they have had to adapt to nearly every type of
marine environment.
Ichthyology: The scientific study of fishes
Body Shape
The body shape of a fish is directly related to its lifestyle:
 Fast swimmers have a streamlined body shape that helps them
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move through water (sharks, tunas, mackerels, marlins)
Leisurely swimmers (snappers, butterfly fishes) have laterally
compressed bodies that are efficient enough for fast bursts of
swimming to escape predators or capture prey
Demersal fishes (rays, skates) are dorsoventrally flattened
Flat fishes (flounders, halibuts) are flat and adapted to bottom
living, but bodies are laterally compressed
Elongated bodies are characteristic of eels to allow life in narrow
spaces or among vegetation
Some are exceptions to basic shapes (seahorses, trunkfishes)
based on their needs and habitat
Benefits of Body Shape
Body shapes can be beneficial,
regardless of the marine habitat.
They are most useful for
camouflage and concealment
 Pipefishes live among eel grass, in
which they resemble
 Blennies have irregular growths on
their head, which resembles
seaweed
 Stonefishes bodies resemble a rock
so closely that it is almost invisible
to prey and humans!
(Unfortunately, the shallow-water
fish possesses the most potent
venom and is excruciatingly
painful and potentially fatal if
stepped on).
Coloration
Some bony fishes use color for camouflage, but some are the most
brightly colored animals in the sea… like displayed in the tropical
region.
Coloration is found in special cells in the skin called
chromatophores. Chromatophores are irregularly shaped and have
branches radiating from the center. The amazing colors results from
a combination of chromatophores with varying amounts of
pigments.
Some fishes can change color by contracting and expanding the
pigment in chromatophores.
Fishes may also have structural colors that result from reflecting
certain colors of light. Most structural colors come from a sequence
of crystals that act like tiny mirrors. These crystals are called
iridophores.
Do Colors Mean Anything?
Colors can tell a lot about fishes:
 Some change colors with their mood or reproductive
condition
 Some use color to advertise they are dangerous, poisonous, or
taste bad (warning coloration)
 Some blend with the environment to deceive predators or prey
(cryptic coloration)
 Some use the presence of a color stripe, bar, or spot to help
break up the outline of the fish (disruptive coloration)
 Some use color as a disguise in open-water, for concealment
(countershading) by having a lighter belly than back
Locomotion
Swimming is a major part of the life of fishes. They swim to
obtain food, to escape from predators, and to find mates.
Some fish also swim to flush their gills with water to obtain
oxygen.
Most fishes swim in a rhythmic side-to-side motion of the body
or tail. They form S-shaped waves of contractions from their
head to tail and push against the water to force the body
forward.
Rhythmic contractions are produced by bands of muscle called
myomeres, which run along the sides of the body. The
myomeres are attached to the backbone for support and make
up a large percentage of the body weight of a fish.
Swim Bladders
Swim bladders provide bouyancy in bony fishes.
Fish who do not have a swim bladder tend to sink so they
must compensate with fins.
 For instance, the shark has large, stiff pectoral fins that
provide lift like the wings of a plane. In addition, sharks
have liver oil to provide some bouyancy because it is less
dense than water
 Rays and skates use their pectoral fins as their main source
of lift, like wings of a bird
Maneuverability
Because bony fish have swim bladders to provide bouyancy,
they can use their pectoral fins for other purposes.
 Hovering in one location
 Swim backwards (sharks cannot do this)
 Steer and provide stability
 Turn, balance, and “brake”
 Gliding through the air (flying fishes)
 Crawling or resting on the bottom (gobies)
 Attaching to rocks (clingfishes)
 Attaching to sharks (sharksucker)
Flying Fish
Clingfish
Sharksucker
Catalina Goby
Feeding: Cartilaginous Fishes
 Most sharks are carnivores, but in
contrast to typical carnivores who
capture smaller prey sharks feed by
taking bites from prey larger than
themselves. Because of this, almost
anything can be found in a shark’s
stomach
 Several species are filter feeders,
such as the whale shark, the manta,
and devil rays. These fish filter
water with gill rakers (slender
projections on the inner surface),
which determines the size of food
captured. They primarily feed on
squid, schooling fish and plankton.
They are also known to swim
leisurely with their mouths open,
taking in everything they can.
Feeding: Bony Fishes
Bony fish are diverse in the way they feed:
1. Carnivorous
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Capture their prey with well-developed teeth to grasp and
hold them before they swallow them whole
2. Grazers
 Front teeth are fused to form a beak-like structure to
scrape off food
3. Plankton Feeders
 Filter plankton with gill rakers, typically “straining food”
with their large mouths open
 Most abundant fishes in the ocean
 Important food source for carnivorous fishes
Behavior
Nearly all aspects of the lives of fishes involve complex
behavior:
 to adapt to light and currents
 to find food and shelter
 to avoid predators
Territoriality
Many marine fishes do not reside in any particular area; however, some are
known to establish territories in which they defend against intruders.
Reasons for Territories:
 Territories only during reproduction
 Permanent territories that they use for feeding
 Permanent territories used for resting and shelter
Fishes defend territories individually or in male-female pairs and often times,
territories are shared with other organisms through division of
subterritories.
It is believed that fish often guard territories to ensure they have enough food
and other resources and they are therefore crowded environments where
resources are likely in short supply. Sometimes, fish are known to fiercely
defend their territories, often attacking other fishes or divers in their
“space”.
Defending Territories
Fishes use a variety of aggressive behaviors to defend their
territories:
 Bluffing – raising fins, opening mouths, rapid darting
about (actual fights are rare)
 Sound production – grinding teeth, rubbing bones or fin
spines, or “drumming” (pulling muscles on the swim
bladder to amplify sounds)
Schooling
Many fishes form well defined groups (schools) that function as
coordinated units although there are no “leaders”
Characteristics:
 Some school throughout their lives, but adult schools are most
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common with around 4000 species
Schools can be huge (Atlantic Herring)
Members of a school are generally the same size
Fishes within a school keep a constant distance between
themselves, turning, stopping, and starting in nearly perfect
unison
Vision plays an important role in schools, although some blinded
fish can school through use of their lateral line and senses as a
means of keeping track of one another.
Why Do Fishes School?
There is no single reason that fishes school, but some are
detailed below:
 To provide protection against predation (strength in
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numbers)
To confuse predators (some will become confused when the
school circles the predator or splits into several groups)
It is difficult for the predator to pick just one when they are
circling, darting, and shifting in a group
Increases the swimming efficiency of the fish because the
fish in front reduce water resistance for those behind them
In some species, schooling is advantageous for feeding and
mating
Migrations
Another fascinating aspect of the behavior of marine fishes
is migration (mass movement from one place to another
once a day, once a year, or once in a lifetime).
Many open-water fishes migrate up and down the water
column every day; however, the most spectacular
migrations are the transoceanic journeys made by tunas,
salmon, and other fishes.
Although we do not fully understand reasons why fishes
migrate, we know that they are connected to meeting the
needs of feeding and reproduction.
Migration for Feeding
Recaptures of tagged fish
have provided information
on how far, how fast, and
when tunas migrate.
Tunas have been known to
migrate long distances to
feed in temperate water
(Skipjack Tuna)
Migration for Reproduction
Anadromous fishes spend their lives
at sea, but move to freshwater for
reproduction.
The most well-known anadromous
fish is the salmon.
Characteristics of Migration:
 Use chemical memory to find
their “home stream” by
recognizing smells of the stream
and streams along the way
 Do not feed in freshwater, live on
stored fat
 Kidneys are able to adapt to
change from saltwater to
freshwater
Basic Reproduction
Reproduction in fishes requires a number of adaptations of the
reproductive system and the behavior that brings the two sexes
together to ensure success.
Timing is essential, potential mates must get together at the right time
to breed. Many will congregate in breeding grounds while some
come only during breeding season. Many fishes will stop feeding
during breeding season in order to put all “focus” on reproduction.
Courtship is also a necessary component of reproduction, which is a
series of behaviors that are displayed to attract mates. These involve
an exchange of “dances”, special postures, changing colors, or
swimming upside down. Each species has its own unique behavior,
which is thought to keep members from mistakenly mating with the
wrong species.
Mandarin Fishes
Courting Rituals
Mandarin females gather in groups
of 4-5 in one location each day.
Males frequent the area, performing
dances to attract them. Once a
female selects a male (larger males
are favored) they spawn by the
female resting on his pelvic fin. The
pair slowly rises about three feet
above the coral reef, where they
release a cloud of eggs and sperm.
Smaller males, because not often
selected, will “streak” the area by
rushing up to the mating couple
and releasing their own sperm in
hopes of fertilization.