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Chapter 8
Marine Fishes
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Evolved more than 500
million years ago from
invertebrate chordate, most
economically important
marine organisms
Vertebrates: an introduction
3
Subphylum Vertebrata
have backbone (or vertebral
column, spine or vertebrate) used
to protect nerve cord, or spinal
cord(脊椎)
bilaterally symmetrical body
presence of an endoskeleton
4
Fishes are oldest and
structurally simplest of all
living vertebrates, most
abundant vertebrates, in term of
both species of individuals.
5
At least 30000 species, comprise half of the
vertebrates species on earth, 15300 are
marines
-- Three groups
recognized
Jawless fishes
Class Agnatha (原口綱)
• Most primitive fishes
• No jaw, feed by suction with the aid
of a round, muscular mouth and row
of teeth
• Body is cylindrical and elongate like
eels
• Lack of paired fin and scale
• Lack of true vertebrate
8
Hagfihses (slime eel;點盲鰻)
Hagfihses (slime eel)
Feed mostly on dead or dying fishes
Live in burrow and dig in muddy
bottom, mostly at moderate depth in
cold waters
About 20 species
Growth up to 80 cm
10
Lamprey
-- Found in most temperate regions, primarily
freshwater fishes; ectoparasite
-- about 30 species
Cartilaginous fishes
Class Chondrichthyes
Figure 8.05b
Sharks
Skate (魟)and Ray(蝠魟)
Figure 8.07
Ratfish
Cartilaginous fishes
• skeleton made of cartilage; that is
lighter and more flexible than bone,
• movable jaw usually armed with welldeveloped teeth
• presence of paired lateral fins for
efficient swimming
16
-- Mouth is almost always ventral
Cartilaginous fishes
-- have the placoid scales(盾鱗), which pointed
tip directed backward; same composition
as teeth
Sharks
-- adapted for fast swimming and predatory feeding
-- evolved over 100 million years ago; “living fossil”
Sharks (morphology)
• Fusiform or spindle-shaped bodies
• Tail or caudal fin is well developed
and powerful; usually heterocercal in
shape
• have a pair of dorsal fins
• paired pectoral fins are large and
pointed
• five to seven gill slits are present
20
Sharks (others)
• Triangle teeth embedded in a tough, fibrous
membrane that cover the jaw
• About 350 species
• Found throughout the ocean at all depths;
predominant in tropical coastal waters
• Primarily marine, few travel far up river
• Shark fish for meat, oil, fin and skin
• Overfishing led to management of shark
fishing; include ban on shark fin international
trade.
21
Basking shark
Whale shark
Great white shark
Skate (魟) and Ray
-- about 450 to 550 species
Skate and Ray
• Dorsoventrally flattened bodies
• Most live on bottom as demersal fishes
• 5 pairs of gill slits, on the underside of the
body,
• Pectoral fins are flat and greatly expanded,
and fused with the head
• Eyes are usually on top of the head.
• Feed on fish
• Grow up to 11 m
25
Stingrays
Stingrays
 Have whip-like tail, equipped with stinging
spines for defense; contain poison glands
 Feed on clams, crabs, small fishes and other
animal live in sediment
27
electric ray
-- can produce 200 volts electrcity
Skate
lack of whip-like tail and stinging spines,
lay egg cases, and give birth to live young.
Figure 8.07
Ratfishes or chimaeras
Ratfishes or chimaeras




About 30 species
have only one pair of gill slit,
covered by a flap of skin
have a long rat-like tail
feed on bottom-dwelling crustaceans
and mollusks
32
Bony fishes
Class Osteichthyes
Skeleton made at least partially of bone
About 23000 species, comprise 96% of all
fishes and almost half of all vertebrates,
and a little more than half of them live in
ocean
33
Usually have cycloid or ctenoid scales(櫛鱗); which are
made of bone and are covered by a thin layer of
skin and protective mucus
-- presence of operculum (gill cover)
Bony fishes
• upper and lower lobes of caudal fins are the
same size; homocercal
• fins are supported by bony spines or fin rays;
consist of rigid spines for protection, propulsion
and maneuverability
• mouth located at the anterior end
• jaws have more freedom of movement than
those of the shark
• teeth are generally attached to the jawbones
• have swim bladder, which allow fish to adjust its
buoyancy to keep from sinking or rising.
35
Biology of fishes (ichthyology)
36
Body shape
-- body shape is directly related to its lifestyle
-- fast swimmers have a streamlined body shape,
that helps them move through the water
-- laterally compressed bodies good for leisurely swimming
around coral reefs, kelp beds, or rocky reefs
-- efficient for escape and capture foods
Figure 8.09c
Many demersal fishes are dorsoventrally
flattened from top to bottom
Figure 8.09d
Eel-like fishes, often live in narrow spaces
in rock, coral reefs, or among vegetation
Body shape may be especially useful for
camouflage, for catch prey
Stonefish
Coloration
Colored pigments are found in
speciacells in the skin called
chromatophores(色素細胞)
-- These cells are irregular in shape and have branches
Combination of chromatophores with varying
amount of different pigments give variety
color of fishes
Fish also have structural color, result when a
special surface reflects only certain colors of (bkg) light
-- due to crystals that contained in special
chromatophore called iridophores (虹細胞)
43
Some change color with their mood or
reproductive condition
44
Some fishes have warning coloration
45
Cryptic coloration, blending with the environment
46
Disruptive coloration, help break up the outline of a fish;
common among coral reef fishes
47
Open-water fishes and many shallow-water predator have
silver or white bellies in shape contract to dark backs called
countershading
Deep-water fishes also use color for concealment;
dark or red in color
48
Locomotion
-- Swimming for obtain food, escape predator, find
mate and obtain oxygen
-- Rhythmic S-shaped waves
Figure 8.12a
rhythmic contraction are produced by bands of muscles
called myomeres (肌節)
Figure 8.12b
Myomers are attached to backbond for support
-- Muscle made up large percentage of body weight
-- Shark have large, stiff pectoral fins that provide lift, and longer
upper lobe of the tail tends to tilt the body upward, also
generating some lift
-- Large amount of oil in liver provides buoyanccy
-- In ray and skates, tail is reduced and pectoral fins
for lift and thrust
In bony fishes, dorsal fns anal fins are used to steer and provide stability
and the pelvic fins (腹鰭) also help fish to turn, balance and brake
-- Most bony fishes have a swim bladder
Locomotion
 The flexibility of fins allow many fishes
to depart from the standard
undulating(波浪形) style of swimming
 Swimming mainly by moving their fins
rather than their bodies
 Tails used solely as rudders(舵)
54
Feeding (filter feeding)
 Basking shark filter the water with gill
rakers
 Whale sharks have filter plate made of
modified placoid scale
 They both have many small teeth and very
long gill slits
55
Filter feeding
 The width of the space between the gill rakers or
filter plates determines the size of the food
captured
 Whale sharks feed in warm water on small
schooling fishes, squids and planktonic
crustaceans.
 Basking sharks live in colder water, feed on
planktons
56
-- Mantas feed on plankton and small fishes; two
fleshy, horn-shaped projections help channel
food into the mouth
Bony fishes have protrusible jaws,
which allow more flexibility in feeding,
thus most bony fishes are carnivores
58
Figure 8.13a
They are typically have well-developed teeth for catching, grasping,
and holding prey. The mouth roof, gill rakers, and pharynx may also
have teeth to help hold the prey.
Bottom feeders have a downwardoriented mouth adapted for suck
food from the bottom
60
Figure 8.13d
Fish feed primarily on seaweed and plants are known as grazers(吃草的);
beak-like structure; which used for scrape off bits of live coral.
Figure 8.13e
Herring and menhaden filter plankton with gill rakers,
swimming with their mouth open
Plankton feeders are the most abundant fishes in
the ocean, are an important food source for many
types of carnivores.
They also account for a large share of the
world’s fish catch.
63
Digestion
stomach is used for digestion,
typically J-curved or elongate but
may be modified into grinding
structure or even lost together
64
In most bony fish, the anterior portion of the intestine has many
slender blind tube, the pyloric cacea (幽門囊), which secrete
digestive enzymes
65
Digestion
• Other digestive enzymes are secreted by
the inner walls of the intestine and the
pancreas.
• Liver secretes bile needed for the
breakdown of fats
• Carnivorous fishes have short, straight
intestine, while herbivorous fishes have
coiled intestine.
66
The intestine is responsible for absorbing the nutrients
-- The intestine of cartilaginous fishes and a few primitive
bony fish contain spiral valve; increase internal
surface area
Figure 8.15
Circulatory system
-- All fishes have a two-chambered heart located below the gills
Figure 8.16a
Respiratory system
-- Irrigation of the gills
-- Most sharks swim with their
mouth open and close, force
water through the mouth and
gills
Figure 8.16b
-- The expansion and contraction of the pharynx wall
and gill silt assist the pumping of water
-- The first pair of gill slit of cartilaginous fish is modified
into spiracles(呼吸孔), it locates on the dorsal surface of ray
and skates, allows fish to respire even lie on the bottom
Figure 8.17a
-- For many bony fishes,
the gill opening is
covered by an
operculum structure
of the gills
Figure 8.17b
-- Fish gills are supported by cartilaginous
or bony structure, the gill arches
-- Each gill arch bears two row of slender
fleshy projections called gill filaments
-- Gill rakers(鰓杷) projects along the inner surface of the gill arch;
prevent food particles from entering and injuring the
gill slits, or may be specialized for filtering feeding
Each gill filament contains many rows of thin plates
or dishes called lamellae(薄片), contains capillaries; can
greatly increase the respiratory surface.
--The number of lamellae is higher in active swimmers
Figure 8.17d
Gas exchange
-- Oxygen is diffuse into
the capillaries of the gill
filaments
Figure 8.17e
Fishes have evolved a countercurrent system
of flow in increase efficiency to extract oxygen
Gas exchange
• Oxygen carried through the body vie
hemoglobin, which is contained in
specialized cells called erythrocytes or red
blood cell
• After hemoglobin give off the oxygen, it
picks up carbon dioxides and carried to
the gills
• Muscles have myroglobin to store oxygen
78
Regulation of the internal environment
-- blood of bony fishes is less salty than seawater,
thus they need osmoregulate their blood
-- kidney conserve water by produce small amount of urine
Excretion of excess salt
 some pass straight through the gut
 some absorb and excrete by the kidney and
specialized chloride cell in the gill
80
Cartilaginous fishes reduce osmosis by increasing the amount of
dissolved molecules or solutes in the blood, making the blood
concentration closer to the seawater
-- Amount of urea in blood is controlled by the kidney
-- Cartilaginous fish also absorb water to
prevent dehydration, through the
gill and from food.
-- Excess salts are excreted by the
kidney, intestine and rectal gland(直腸腺)
82
Nervous system and sensory organs
Vertebrates have the most
complex and advanced
nervous system of all animal
groups
(A) It has central nervous system,
consist of brain and spinal cord



Used to coordinates and integrates
all body activities and to store
information
Brain is divided into several region
serve as center for various functions
and is protected by a cartilaginous
or bony skull
Information is sent to the brain in
the form of nerve impulse
84
(B) Most fishes have a highly developed
sense of smell, use to detect food,
mates, predators, and find their way
home
85
sensory organs
• olfactory sacs; locates on both sides of
the head, reach outside vie one or two
openings, the nostrils or nares; welldeveloped in shark
• test buds; located in the mouth and on
the lips, fins and skin, as well as barbells
• Bony fish rely on vision more than
cartilaginous fishes
86
Why fish eye are bulge in shape ?
Eyes on most land vertebrates
focus by changing the shape of
the lens, the round lens of the
fish eye focuses by moving
closer or father away from the
subject
Vision
Some sharks have nictinating
membranes, can be drawn
across the eye to reduce
brightness and to protect the
eye during feeding
Figure 8.19
lateral line, to detect vibrations in the water
-- the small canal that run along the head and body, with
cluster of sensory cell or neuromasts (神經瘤)
-- allows fishes to avoid obstacles, and predator,
detect prey, orient to currents and keep
their position in school
Cartilaginous fishes have sense organ
called the ampullae of Lorenzini, detect
weak clectric field; locate prey and help
navigation or detect the current
90
Fish perceive sound waves with
inner ears
 Paired hearing organs located on the side of the
brain just behind the eyes
 Inner ears are a set of fluid-filled canal contain
sensory cells
 The inner ear is also involved in equilibrium and
balance, have calcareous ear stones, or otoliths
91
Involve complex behavior to (1) adapt light and
current, find food, shelter and avoid predator, (2)
courtship and reproduction, (a) Territority
Behavior
Territority
• Some fishes defend territories during reproduction
• many have more or less permanent territories, use
for feeding, resting or shelter
• most common in crowded environments like kelp
beds, and coral reef, where resource is in short
supply
• Fish use aggressive behaviors to defend their
territories; gesture and sound
• defend by solitary individual, or a male-female pair
• Demersal fish can divide the territory into
subterritory
93
Schooling
Schooling
• Many fishes form well-defined groups
• Some school throughout their lives, others
part time as juvenile or during feeding
• Most cartilaginous fishes are solitary
• Many marine and freshwater species
school as adult
• Stationary school common around coral
reef, kelp beds, rocks, shipwrecks; include
different size or species
95
Schooling
• Vision plays an important role in the
orientation of individuals within a school;
blind fish use lateral line, olfaction, and
sound they emit to orient
96
Figure 8.21b
Schooling break down when they are feeding or attach by a predator
Functions of schooling:
 Protection against predation
 Increase swimming efficiency; because the
fish in front from an eddy that reduce water
resistance for those behind
 Advantageous in feeding or mating
98
Migrations
• Definition: regular mass movements from
one place to another once a day, once a
year, or once in a life time
• feeding is the main reason behind the
migration of open water species
99
Figure 8.22
Some species migrate from tropical waters
to temperate water
Migration clues
•
•
•
•
•
•
•
•
land features
current
Water characteristics
salinity
temperature
light
sun
earth magnetic field
101
Migration between marine
and freshwater
102
Anadromous
103
Anadromous

migrate to freshwater to spawn

Mechanisms

Homing behaviour; ability of an animal find its
way back to a home area
104
Hazards to anadromous fishes




Route blocked by dams
Spawning ground filled with silt; logging and
cattle grazing
River polluted by pesticides, fertilizers,
animal wastes
Total ban on harvest in Oregon and California
since 2008
105
Figure 8.24
Catadromous: breed at sea and migrate into
river to grow and mature
Catadromous






Spawn at depth of 400 to 700 m
Developed into leptocephalus larvae (柳葉幼
魚)
American eel stay for 1 year, European eel
stay 2-3 more years
Migrate to freshwater to growth
Stay in freshwater 10-15 years
Migrate to sea to spawn and die
Reproduction and life history
• Reproductive system
• Reproductive behavior
• Early development
108
Reproductive system
• Sex are usually separate
• Both sexes have paired gonads located in
the body cavity
109
Reproductive system
• In cartilaginous fishes, ducts lead from
ovaries and testes into the cloaca
110
Reproductive system
• For jawless and bony fishes, they have a
separate opening for urine and gametes,
the urogenital opening(泌尿生殖孔),
located just behind the anus
111
Reproductive system
• Timing of gamete production is crucial;
both sex ready spawn at the same time
• The reproduction season have to match
the production season; spawning must
take place during the most favorable
conditions
112
Reproductive system
• Timing of reproduction is critical for fishes
that make long migration to breed
• Timing of reproduction is controlled mostly
by sex hormone
• Can stimulates the maturation of gametes,
and cause change in color, shape, and
behavior before breeding
• Release of sex hormone is triggered by
environmental factors
113
Hermaphroditism
• self-fertilization rare occurs (cross-fertilization)
• found among deep-water fishes; because it is
difficult for them to find mate
• sex reversal or sequential hermaphroditism;
controlled by sex hormone, but triggered by
social cues; e.g. absence of a dominant male
114
Figure 8.25
Reproductive behavior
Reproductive behavior



11
6
Many species migrate and congregate in
specific breeding ground
Many of them appear to stop feeding at
spawning time
Many bony fishes change color to advertise
their readiness to breed
The first step in reproduction is courtship; to keep
fishes from mistakenly mating with other species
117
Reproductive behavior
• Some fishes have internal fertilization; through the act of
copulation; by clasper in cartilaginous fishes
118
Reproductive behavior
• For external fertilization, broadcast
spawning
119
Reproductive behavior
• Open water fishes and those living around
coral reefs and inshore environment;
spawn directly into the water after
courtship
• For some fishes, individual males may
establish territories or aggregate into
group prior to mating
• Eggs fertilized in the water column drift in
currents and develop as part of the
plankton, called broadcast spawner
120
Reproductive behavior
• Some spawn in pair
121
Reproductive behavior
• Most eggs contain oil droplets and are buoyant,
others are sink to the bottom
• Fishes that spawn fewer and larger eggs, they
will either guard the
eggs or carry the eggs
after they have fertilized
122
Early development
 Oviparous;
most bony fishes are oviparous
 Ovoviviparous
 Viviparous
 Pathenogenesis
123