Transcript 320Zoo

Ichthyology Course
Zoo 320
Position of Fish in the Animal Kingdom
Phylum: Chordate
Subphylum (1): Vertebrata (animals have a dorsal cord, notochord, vertebrae)
Superclass 1: Gnathostomata (craniata = have cranium, jaws)
Class (1): Osteichthyes (bony fish = teleosts)
Class (2): Chondrichthyes (cartilaginous fish as sharks and rays=elasmobranchs)
Class (3): Actinopterygii
Class (4): Crossopterygii
Class (5): Amphibia
Class (6): Reptilia
Class (7): Aves
Class (8): Mammalia
Superclass 2: Agnatha (acraniata = no cranium, no jaws)
Order: Cyclostomata (Lamprey, petromyzon, Hagfish)
Subphylum (2): Hemichordata
Subphylum (3): Cephalochordata
Subphylum (4): Eurochordata (tunicate)
Basic methods of fish taxonomy ‫تصنيف‬
(Identification of a fish)
1) Morphometric
measurements
‫قياس‬:describe the external features of a fish
(metric= non meristic),
Body measurements: T.L, S.L, F.L
or ratios: Cephalic index (H.L/T.L), interorbital
index (I.O width/H.L)
2) Meristic counts ‫ عدد‬:- rays and spines on
lateral line, gill rakers, number of scales
A diagram of general fish morphology
These are generalised diagrams on the shape of bony fish. There are great number of
differences between species. These differences can relate to body shape, relative size
of each fin, Number of rays, colour, shape and function, as well as internal structure
and positioning of the organs.
These diagrams are based on the typical shape of bony fishes.
Basic methods of fish taxonomy
(Identification of a fish), cont……
3) Anatomical features (internal str. of fish), e.g:a) Shape & position of the lateral line differ
from sp. to another.
b) Shape & position of internal organs (ratio
between esophagus length: stomach).
c) Shape of pyloric caeca differs from gp. To
anther.
d) Secondary sexual characters (lower jaw is
elongated during copulatory season in some
spp.)
Basic methods of fish taxonomy
(Identification of a fish), cont……
4) Colour pattern:e.g:- The color of fish differs from fish to
another.
- Also, it may differs from male to female
(sexual dimorphism).
5)Karotypes:- Describe the genetic properties, as :- the
number of chromosomes, arrangement of
genes on the chromosomes & amount of
DNA.
Basic methods of fish taxonomy
(Identification of a fish), cont……
6) Biochemical method:Is done by electrophoresis.
e.g:- the number and the arrangement of
aminoacids in protein is useful to detect
genetic variations.
Basic methods of fish taxonomy
(Identification of a fish), cont……
7) Speciation (geographic isolation):- (The evolutionary
formation of new biological species, usually by the
division of a single species into two or more
genetically distinct ones).
Sympatric speciation: (A speciation in which new species
evolve from a single ancestral species while inhabiting
the same geographic region) i.e (to the same area).
Allopatric speciation: (A speciation occur in small
populations that have become separated from the
main populations, individuals of the population can no
longer interbreed) i.e (to a different area).
-AGAIN–
Position of Nekton in the Animal
Kingdom
Phylum: Chordate
Subphylum (1): Vertebrata (animals have a dorsal cord, notochord, vertebrae)
Superclass 1: Gnathostomata (craniata = have cranium, jaws)
Class (1): Osteichthyes (bony fish = teleosts)
Class (2): Chondrichthyes (cartilaginous fish as sharks and rays)
Class (3): Actinopterygii
Class (4): Crossopterygii
Class (5): Amphibia
Class (6): Reptilia
Class (7): Aves
Class (8): Mammalia
Superclass 2: Agnatha (acraniata = no cranium, no jaws)
Order: Cyclostomata (Lamprey, petromyzon, Hagfish)
Subphylum (2): Hemichordata
Subphylum (3): Cephalochordata
Subphylum (4): Eurochordata (tunicate)
Phylum Chordata found in the fresh and salt
waters of the world. Living species range
from the primitive, jawless lampreys and
hagfishes through the cartilaginous sharks,
skates, and rays to the abundant and diverse
bony fishes.
FISHES
• Main Characters:•
•
•
•
•
All fish live in water
Have gills
Have fins (rays-spines)
Scales (sometimes not exist)
Finfish can be further subdivided into demersal fish (living
on or near the sea bed and including round and flat white
fish, less fat fish) and pelagic fish (living in mid-water or near
the surface and including oil-rich fish).
Bony Fish (Class: Osteichthyes, Teleosts):
Members of this class characterized by-:
1) Bony skeleton
2) Fins, may be:Paired fins (one fin on each side of the fish), as pectoral fins
and pelvic fins.
Unpaired fins (one fin in all the body) as dorsal, caudal and
anal fins.
3) Scales: are used to determine the fish age. May be cycloid or
ctenoid.
4) Caudal peduncle: as it is thinner the fish becomes faster.
5) Presence of gas bladder
Class (1): Osteichthyes (bony fish = teleosts)
A diagram of general fish morphology
These are generalised diagrams on the shape of bony fish. There are great
number of differences between species. These differences can relate to
body shape, relative size of each fin, Number of rays, colour, shape and
function, as well as internal structure and positioning of the organs.
These diagrams are based on the typical shape of bony fishes.
one gill opening on either side, sometimes
tiny, or only single opening on throat
Dissection of a bony fish
Blue Mackerel
Cut along isthmus
Cut posterior end of gut
Incision at anus
Body cavity
Pull gut forward
Cutting anteriorly
Cut between pelvic fins
Internal
organs
Swim bladder exposed
Pull aside gut
Cutting operculum
Gills exposed
A diagram of the internal structure in a typical bony fish.
Class (1): Osteichthyes (bony fish =
teleosts)
• characterized by :• a relatively stable pattern of cranial bones,
insertion of mandibular muscle in lower jaw.
• head & pectoral girdles are covered with large
dermal bones. The eyeball is supported by a
sclerotic ring of four small bones, but this
characteristic has been lost or modified in
many modern species.
The labyrinth in the inner ear contains large
otoliths. The braincase, or neurocranium, is
frequently divided into anterior and posterior
sections divided by a fissure.
Class (1): Osteichthyes (bony fish =
teleosts)
• ray-finned fish (subclass: Actinopterygii)
• lobe-finned fish (subclass:
Sarcopterygii=Crossopterygii), 8 spp. including
lungfish.
subclass: Sarcopterygii
• lobe-finned fish have a fleshy lobe at the base
of their fin.
• The lobe possesses musculature & skeletal
elements, which can provide more support
than the ray-finned fish can. Thus, they can
use their fins to cruise slowly through
shallows, or even through muddy pools or
even over dry land for short periods.
• These lobes gave rise to the tetrapod limbs
common to all terrestrial vertebrates.
subclass: Sarcopterygii
• Today, the only living species of lobe-finned
fish are the lungfish (Dipnoi) and the
coelacanth (Latimeria), but there were more
in previous eras.
Lungfish
Latimeria
subclass: Actinopterygii
• Ray-finned fish (Actinopterygii) are the
dominant aquatic vertebrates today. They
illustrate great diversity in their morphology
and habitats, living in shallow to deep and
freshwater to marine habitats. Their name
comes from the presence of “rays,” fine bony
or horny spines that support the webbing of
their fins. Trout, salmon, bass, and tuna are
typical modern ray-finned fish
Cartilagenous Fish (Class: Chondrichthyes)
The Chondrichthyes ro cartilaginous fishes dewaj era
-owt ,selacs ,slirtson deriap ,snfi deriap htiw hsfi
egaltirac fo edam snoteleks dna ,straeh derebmahc
.enob naht rehtar
This Class could be divided into 2 subclasses:
S. Class 1:- Elasmobranchii
(e.g: rays, skates and sharks)
S. Class 2:- Holocephali
(e.g: chimeras = ghost sharks = elephant fish)
General characteristics:
*Animals from this group have a brain weight relative to body
size that comes close to that of mammals, and is about ten
times that of bony fishes, One of the explanations for their
relatively large brains is that the density of nerve cells is much
lower than in the brains of bony fishes, making the brain less
energy demanding and allowing it to be bigger.
*Their digestive systems have spiral valves, and with the
exception of Holocephali, they also have a cloaca.
* In rays, the pectoral fins have connected to the head and are
very flexible.
*As they do not have bone marrow, red blood cells are
produced in the spleen and special tissue around the gonads.
They are also produced in an organ called Leydig's Organ
which is only found in cartilaginous fishes.
*A spiracle is found behind each eye on most species.
*Their tough skin is covered with dermal teeth (again with
Holocephali as an exception as the teeth are lost in adults,
only kept on the clasping organ seen on the front of the
male's head), also called placoid scales or dermal denticles,
making it feel like sandpaper. It is assumed that their oral
teeth evolved from dermal denticles which migrated into the
mouth.
S. Class 2:- Holocephali
e.g: chimeras
The chimaeras are characterized by having tooth
plates in their mouths for crushing hard food
and a dorsal spine with a venom sac at its
base. They are found in deep subarctic and
Antarctic waters and are an evolutionary
backwater. Outside the breeding season they
live on the continental shelf up to 200 metres
deep.
• They may be the "oldest and most enigmatic
groups of fishes alive today. At one time a
"diverse and abundant" group (based on the
fossil record), their closest living relatives are
sharks, though in evolutionary terms they
branched off from sharks nearly 400 million
years ago and have remained isolated ever
since.
• Like other members of the class
Chondrichthyes, chimaeras have a skeleton
constructed of cartilage. Their skin is smooth
and largely covered by placoid scales, and
their color can range from black to brownish
gray. For defense, most chimaeras have a
venomous spine located in front of the dorsal
fin.
Chimeras & Bony Fish
• However, they resemble the bony fishes in
having the upper jaw fused to the skull, the
gill slits opening into a single chamber, a bony
covering (operculum) over the gill slits, and
separate anal and urogenital openings.
Chimeras & Shark
• chimaeras have an extra claspers in the male,
one in front of each pelvic fin and a prominent
one on the forehead.
• Chimaeras resemble sharks in some ways:
they employ claspers for internal fertilization
of females and they lay eggs with leathery
cases. However, unlike sharks, male chimaeras
also have retractable sexual appendages on
the forehead (a type of tentaculum)[5] and in
front of the pelvic fins.
S. Class 1:- Elasmobranchii
(e.g: rays, skates and sharks)
Members of this subclass characterized by-:
)1 Have no swim bladders.
)2 Have five to seven pairs of gill clefts opening individually to the exterior.
)3 Have rigid dorsal fins, and small placoid scales .
)4 The teeth are in several series; the upper jaw is not fused to the cranium,
and the lower jaw is articulated with the upper .
)5 The inner margin of each pelvic fin in the male fish is grooved to constitute
a clasper for the transmission of sperm .
)6 These fishes are widely distributed in tropical and temperate waters.
7) Have a flexible skeleton made of cartilage. For this reason, they are known
as cartilaginous fishes.
8) In Rays and skates are dorsally compressed. Pectoral fin is modified for
swimming.
Class (2): Chondrichthyes (cartilaginous fish)
A diagram of general Ray morphology
5 pairs of gill openings
on underside of head
A diagram of general Shark morphology
5 gill openings laterally on either side of head
or body
Demersal fish
• They are slow moving, dorso-ventrally flattened and bottom
feeding fish. The mouth is fully or slightly vented towards
ventral side. The dorsal side of body is relatively dark; they are
either carnivores or detritus feeders. The young spends early
life at the pelagic level.
• Marine fish production largely depends on presence of
demersal fishes. However, though they are bottom dwelling
fish, only a few species live at great depths of the sea floor,
and these fishes have almost no commercial importance
(Demersal fish of commercial interest are mainly confined to
the upper 200 m, the rest are used as a fish meal).
• Those fish found living on or near the bottom of the sea. They
contain little oil (1-4% fat) and called Non-oily fish
• e.g. cod, dogfish, haddock, halibut, plaice, saithe, skate, sole,
Sea Catfish, Jewfish, Silvery Croaker, Seabream, Perch, Eel,
Grouper, Silver Bream, Indian Barracuda, Black Bass, Rabbit
Fish, Crab Eater, and whiting. Several species of sharks also
live near the bottom and can be grouped as demersal fishes
• The deep-water demersal fishes are generally divided into
two categories, benthic and benthopelagic. The benthic fishes
are those that have a close association with the seabed and
include species such as skates and flatfishes. Benthopelagic
fishes are those that swim freely and habitually near the
ocean floor and, in the areas where deep-water fisheries are
commercially viable, they comprise most of the exploited
biomass.
Milk fish
Cat fish
Solea sp.
Devil rays
Morphology of the fish
• Bony or cartilagenous, within each type there
are variations in external shapes or
morphology (fusiform”common form”,
depressiform, compressiform, anguilliform,
sagittae form).
Fins and their modifications
• Types:Paired (pectoral, pelvic)
Unpaired (dorsal, anal, caudal)
1) Dorsal fin: used to facilitate its advance in
water.
* Anguilla sp., poisonous fish, spiny-rayed fish,
soft-rayed fish, remora, rays, bottom fish.
2) Pelvic fin: making balance, generally behind
the pectoral fin but there are some
modifications (change position).
* Anguilla sp., gobia, rays, Serranus (same
position), Gadus (front of operculum)
3) Pectoral fin: making balance and sometimes
for advancing. Rarely change the position.
* Trigla sp., Exocoetus sp.
4) Anal fin: present between anus and caudal fin. Used
for up and down movement and defense. No change
in position. Consist of spines and rays
* Pipe fish (no anal fin), freshwater species (repr.
organ), eel (elec. Force), cods (more than 1)
5) Caudal fin: consists of 2 lobes (epicaudal and
hypocaudal), help in movement “peduncle”, no
spines. Shapes (homocercal, hetero-, Iso or proto,lepto-)
* eel, hippocampus, Mola sp..
How does the fish move?
1) Fins…..slow movement.
2) Muscles or myotomes……contraction and
protraction
3) Expelling the water through respiration.
Some fish may use the 3 ways or may 1
Ostarcion moves slowly by moving only
the caudal peduncle.
Eeels movement by creations of waves along the
body muscles
• Examples:1) Electric eel:- long anal fin & body create
waves.
2) Amia calva:- long dorsal fin & successive
waves produced.
3) Hippocampus:- moves vertically upward &
downward, moves by successive waves.
4) The sole:- dorsal & anal fins are long, fish
moves by waves produced by these fins.
Summary and comments on Fin roles
• Dorsal & anal fins used for advancing in water.
• Pectoral & pelvic fins used for balancing….
They have no role in advancing EXCEPT in
some swift fish & crescent tail fish,,,, used to
change the direction & advance in water.
• Some spp. can move with low speed, others
as Salmon with high speed ( 10:20 miles/h.).
• Some spp. move vertically, horizontally,
flying, upsidedown, or near the bottom.
Skeleton
Exoskeleton
• Skin
• Membranous
• Integumentory (scales &
spines)
Endoskeleton
• Axial
• Appendicular
Exoskeleton
• Skin:• Consists of 2 layers:- epidermis & dermis
Epidermis
• Is the outer layer of skin
• Contains specialized cells (mucous cells) and
flattened epithelial cells (malpigian layer).
• It has glands that secrete mucous:- cover the skin, composed of mucopolysaccharides .
- reduces the drag of water.
- gives the fish odour by secreting ectohormone
(phermone).
Dermis
• Is the inner layer which contains connective
tissues, nerves, blood vessels, sense organs.
• Function: scale formation.
Skeleton
Exoskeleton
• Skin
• Membranous
• Integumentory (scales &
spines)
Endoskeleton
• Axial
• Appendicular
Exoskeleton
• Integumentory skeleton:• Scales, spines, fin rays and connective tissue
that toughness the skin and joins it to the
underlying musculature, bone and cartilage.
Exoskeleton
• Scales:• Scales represent the exoskeleton structure of
most fish.
• Some fish may be naked (have no scales) as
lampreys & catfish.
• Scales are build up by the connective tissues
of dermis layer.
• Types: Placoid &non-placoid
Exoskeleton
•
•
•
•
Placoid scales (placoid denticle):Exist in cartilagenous fish only
Don’t grow with the growth of fish body.
If lost, not regenerated
Formation of placoid scales
• 1) Odonoblast (from dermal layer) is
differentiated and aggregated.
• 2) Ameloblast (from epidermal layer) modified
to give enamel organ which secretes enamel
layer.
• 3) In the center of each denticle, there is a
hollow pulp cavity contains nerve endings &
blood vessels.
Exoskeleton
•
•
•
•
•
Non-Placoid scales (bony-ridge scales):Exist in bony fish.
Grows with the body growth.
Regenerated if lost
Thin, translucent, so no dentine (enemel
layer)
• The outer layer formed from bony substance
& the inner layer formed of fibrous connective
tissue.
• May be cycloid or ctenoid
• Some spp. Contain 2 types of scales.
• Annulii are formed on scales & used for age
determination.
• Metabolic rate depends on the body
temperature--- as the metabolic rate
decrease, the deposition of circulii
interrupted.
Reasons of false annulii formation:•
•
•
•
•
•
Depression in temp.
Pollution
Diseases
Fish parasites
Reproduction.
;;;;;;;;;;;;;;;;; thus gives false check.
Formation of non placoid scales
• Formed after the fish reaches to a certain size,
so scale growth takes place from under-neath
and margins.
• Epidermis has no role in scale formation.
• Done by aggregation of cells in the dermal
layer (below the epidermis basal membrane),
such aggregation form the focus in the future.
Modification of scales in bony fish:• Serranus spp. Have both types (above lat. line,
ctenoid….. Below it, cycloid)
• Diamond flounder has a tubercles instead of
scales that shines in sunlight.
• Deciduous scales: scales easily
take off as in sardine & anguilla.
- Scales may adhesive together to form a skin
cover as a knife fish or form a complete
exoskeleton as hippocampus.
Modification of scales in bony fish:• In globe fish, there is movable spines as a
mean of defense.
- Scale formula:-
Skeleton
Exoskeleton
• Skin
• Membranous
• Integumentory (scales &
spines)
Endoskeleton
• Axial
• Appendicular
Membranous skeleton
• Connective tissue envelop-joins skin &
appendages to the underlying musculature &
skeletal elements.
• This envelop is continuous at the middorsal &
mid ventral body lines with the median
skeletagenous septum.
• In the tail region, the median septum divides
the fish into 2 lateral halves.
Membranous skeleton
• At the level body cavity-----& from the middle
of each side, of the septum, the horizontal
skeletagenous septum runs from the envelope
to the median septum.
• Thus, there are 4 quadrantes of
muscle mass (i.e the muscles are
separated by myosepta).
Examples of membranous skeleton
• 1- Peritoneal:- covers organs of body cavity.
• 2- Pericardium:- covers the heart.
• 3- Mesentries:- support organs (intestine) in
body cavity.
• 4- Perineural:- surrounds the central nervous
system.
Skeleton
Exoskeleton
• Skin
• Membranous
• Integumentory (scales &
spines)
Endoskeleton
• Axial
• Appendicular
Endoskeleton
A) axial firm skeleton
• Skull:In Lamprey: composed of
- a brain core (neurocranium)
- Sense capsules around sense organs
(olfactory, optic & otic capsules)
- a branchial basket supports pharynx, gill
pouches, face & buccal cavity.
Branchial arches are united & completely fused with cranium
Not segmented
Branchial arches
are united &
completely fused
with cranium
Not segmented
Endoskeleton
A) axial firm skeleton
• Skull:In Sharks (cart. Fish): composed of
- a cartilagenous craniumn (chondrocranium)
- capsules
- Visceral arches (branchiochranium, contains
visceral arches):+ First gill arch--upper & lower jaw (max. & mand.)
+ Second– - suspends the jaws & support
tongue. + 3:7 (5 gill arches)
capsules
• Occipital region: posterior part of brain,
narrow with opening ( foramen magnum),
spinal cord pass through it.
• Otic region: otic capsule enclose internal ear.
• Orbital region: narrow part of the brain for
eye balls… median depression in floor for the
pituitary gland.
• Ethmoid region: expanded part of brain, ends
by a rostrum.
X= nasal capsule
2= orbital region
6= otic capsule
Y= basibranchial
Branchial arches are not united from
the upper side
segmented
Endoskeleton
A) axial firm skeleton
• Skull:In Bony Fish: composed of
- a bony craniumn (neurocranium).
- branchiochranium, 7 branchial arches.
•
•
•
•
•
•
Bones of neurocranium are in:1- Olfactory (nasal area)
2- Otic (about the ear)
3- Orbital (about the eye)
4- Basibranchial (floor of neurocranium)
* In each of these regions, both cartilage &
dermal bones exist.
* In each of these regions, both
cartilage & dermal bones exist.
• Cartilage is deeper than
dermal bone.
• It is first laid down as
cartilage , then replaced
by bone.
• Generally superficial in
position & originates in
inner layers of skin
Major parts of neurocranium
• A series of inner bony elements that provides
a floor to the brain case, surround and protect
Olfactory, optic & otic capsules &anterior part
of notochord.
• A series of outer dermal bones which make a
roof of the brain.
Major parts of branchiocranium
• 1st br. arch constitute Jaws (mandibular &
maxillary).
• 2nd hyoid arch constitute hyal jaws, supporting
hyoid arch & bones covering operculum.
• Branchial arches which support the gills (as
cart. fish, they have 5 br. Arches)
Endoskeleton
A) axial firm skeleton
•
•
•
•
Vertebral column:Composed of vertebrae.
1 vert./ body segment.
Vertebrae are modified according to the body
region.
• In fish, head & trunk moves as a unit, so
there are trunk vertebrae & tail vert.
A) axial firm skeleton
• Vertebra:• Has its body (centrum), has lateral (transverse)
processes that bear ribs (ribs are dorsal or
ventral).
• Above the centrum, there is an
arch that protects the spinal cord.
• Below the centrum in the tail
region, there is an arch which
surrounds caudal aorta.
A) axial firm skeleton
• The rays of the caudal fin are supported by
modified vertebral elements.
• Ribs in fish are dorsal or ventral. The ventral
are present only in bony fish in the trunk
region (within the myosepta of the lateral
muscle bundles).
• The dorsal ribs are also in
trunk region but lie in the
horizontal skeletagenous system.
Endoskeleton
B) appendicular firm skeleton
- Cartilagenous fish:- Median fins:- supported by basal cartilage,
Segmented into Proximal, middle & distal elements.
Endoskeleton
B) appendicular firm skeleton
- Cartilagenous fish:- Pectoral fins:- supported by cartilagenous
girdle,
Consists of upper (scapular) section, & lower (coracoid)
element & in-between,
a glenoid cavity.
Endoskeleton
B) appendicular firm skeleton
- Cartilagenous fish:- Pelvic fins:- The pelvic girdle is a simple
cartilagenous rod called ischiopubic. This
bears the radials supporting the fin ray.
Endoskeleton
B) appendicular firm skeleton
- Bony fish:Pelvic & pectoral fins:- are supported by girdles
Dorsal, anal & caudal:- are supported by bone
series
• Pelvic girdle is composed of:
• 1) a pair of bones (basipterygia) separated or
fused.
• 2) radials which support fin rays, attached
posteriorly to each basipterygium.
• Pectoral girdle is composed of:
• 1) dermal bones:- Post temporal – supra
cleithrum – cleithrum – post cleithra.
• 2) cartilage bones:- paired coracoidsscapulae- 4 pairs of radials.
• Fin rays articulate with the ventral edge of the
scapulae by various
intermediate skeletal
elements.
Dorsal fin
Proximal
Middle
Distal
Patterns of Growth in Fishes
Grow and Survive to Reproduce
Factors Affecting Growth
• Hormones
– Growth hormone secreted by pituitary
– Steroid hormones from gonads
• Temperature
– Most important environmental factor
– Growth increases up to a point
– Fish tend to prefer temperatures where their
growth is maximal
Growth patterns in fishes
• Dissolved Oxygen
– More is better
• Ammonia
– High concentrations slow growth
• Salinity
– Growth is altered when fish are not in their optimum
salinity
Growth patterns in fishes
Competition •
– Generally slows growth
Food •
– Availability & quality affect growth
Photoperiod •
– Longer days increase growth
Growth patterns in fishes
• Age & Maturity •
– Growth is rapid early in life
– With maturity more energy is diverted to gonadal tissue
– Larger fish need more energy to maintain body
Conditioning (Weight lifting for fish??) •
Keys to success:
• GROW
• SURVIVE
• REPRODUCE
Bioenergetic context
Growth is the accumulation of somatic •
(body) tissue that depends on a surplus of
energy consumed
Bioenergetic context
Bioenergetic equation: •
I=M+G+R+E •
I = energy ingested –
M = energy used to maintain healthy tissues –
G = energy for growing somatic tissue –
R = energy for reproduction –
E = energy “lost” through inefficiency of energy –
transfers, etc.
Growth Rate
Anything in the internal or external •
environment that increases or decreases I:
food availability –
competition with other fish for food –
time spent hiding from or escaping predators –
time spent defending a territory –
Growth Rate
• Anything in the internal or external
environment that increases or decreases M:
– temperature
– dissolved oxygen
– toxins - NH4+, heavy metals, organic toxins
Growth Rate
Energy for growth is a tradeoff with energy •
for reproduction
general pattern: grow first, then reproduce –
increased size --> –
increased fecundity (females) •
increased territorial success (males, females) •
increased metabolic efficiency (to a point) •
Fish growth often is periodic
Seasonal variation in temperature, food •
availability, spawning activity, can cause
seasonal growth cessation
(Can you think of examples where this might
happen?)
Fish growth often is periodic
Seasonal variation in temperature, food •
availability, spawning activity, can cause
seasonal growth cessation
If periods are regular (e.g., annual or daily), a •
record of growth and no-growth periods is
formed in hard structures:
scales, fin spines or rays, vertebral centra, –
opercle bones, ear bones (otoliths)
Fish growth often is periodic
Periodic growth marks allow estimation of •
growth rates by counting and measuring
distances between growth checks
Endocrine Growth Regulation
• Pituitary growth hormone:
– increases appetite
– increases food conversion efficiency
– increases production of stomatomedin (stimulate
cell growth and division)
How do different forms of mortality effect overall population
growth??
Internal regulation of growth endocrine system
• Anabolic steriods stimulate growth:
– testosterone in males
– estrogen in females
– corticosteroids in both sexes
Internal regulation of growth endocrine system
Thyroid hormones stimulate growth •
Also regulate metamorphosis •
Fish growth is indeterminate
Growth continues throughout life cycle •
limits to ultimate size are BIOTIC (food –
availability, metabolic efficiency) and not
MECHANICAL (counteracting gravity, etc.)
Fish growth is indeterminate
Advantages to indeterminate growth: •
larger size yields greater efficiency –
Fish growth is indeterminate
• Advantages to indeterminate growth:
– larger size yields greater efficiency
– larger size yields more food options
• faster swimming
• larger gape size
• better sensory range & acuity
Fish growth is indeterminate
• Advantages to indeterminate growth:
– larger size yields greater efficiency
– larger size yields more food options
– larger size reduces number of potential predators
• swimming speed
• gape size
Fish Circulatory Systems 2-chambered heart (1 atrium •
and 1 ventricle
Gills – site of gas exchange•
Fish Respiratory System - gills
O2 and CO2 are exchanged
At finely branched gill
filaments supported by gill
arches
Lungfish
• use gills when in water
• also have lungs
• use lungs to survive times
of no water or low oxygen
• some species must use
their lungs to survive (they drown if
held
underwater)
• some species hibernate when their
ponds dry up (up to 3 years)
THANK YOU FOR YOUR
ATTENTION