Ichthyology Course Zoo 320. Position of Fish in the Animal Kingdom Phylum: Chordate Subphylum (1):...

Ichthyology Course Zoo 320

Position of Fish in the Animal KingdomPhylum: ChordateSubphylum (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): ActinopterygiiClass (4): CrossopterygiiClass (5): AmphibiaClass (6): Reptilia

Class (7): AvesClass (8): Mammalia

Superclass 2: Agnatha (acraniata = no cranium, no jaws)Order: Cyclostomata (Lamprey, petromyzon, Hagfish)

Subphylum (2): HemichordataSubphylum (3): CephalochordataSubphylum (4): Eurochordata (tunicate)

Basic methods of fishتصنيف taxonomy

(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.Lor 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: ChordateSubphylum (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): ActinopterygiiClass (4): CrossopterygiiClass (5): AmphibiaClass (6): Reptilia

Class (7): AvesClass (8): Mammalia

Superclass 2: Agnatha (acraniata = no cranium, no jaws)Order: Cyclostomata (Lamprey, petromyzon, Hagfish)

Subphylum (2): HemichordataSubphylum (3): CephalochordataSubphylum (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, sometimestiny, or only single opening on throat

Cut along isthmus Body cavity Internal organs

Pull aside gut

Cut posterior end of gut Pull gut forward Swim bladder exposed Cutting operculum

Blue Mackerel Incision at anus Cutting anteriorly Cut between pelvic

fins

Gills exposed

Dissection of a bony fish

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 or cartilaginous fishes are jawed fish with paired fins, paired nostrils, scales, two-chambered hearts, and skeletons made of cartilage rather than bone.

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:- Holocephalie.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 openingson 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

protraction3) Expelling the water through respiration.Some fish may use the 3 ways or may 1Ostarcion 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 easilytake 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

EndoskeletonA) 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 craniumNot segmented

Branchial arches are united & completely fused with cranium

Not segmented

EndoskeletonA) 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 capsule2 =orbital region6 =otic capsule

Y= basibranchial

Branchial arches are not united from the upper side

segmented

EndoskeletonA) 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)

EndoskeletonA) 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.

EndoskeletonB) appendicular firm skeleton

- Cartilagenous fish:-- Median fins:- supported by basal cartilage,Segmented into Proximal, middle & distal elements.

EndoskeletonB) appendicular firm skeleton

- Cartilagenous fish:-- Pectoral fins:- supported by cartilagenous

girdle,Consists of upper (scapular) section, & lower (coracoid)

element & in-between, a glenoid cavity.

EndoskeletonB) 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.

EndoskeletonB) appendicular firm skeleton

- Bony fish:-Pelvic & pectoral fins:- are supported by

girdlesDorsal, 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 coracoids-

scapulae- 4 pairs of radials.• Fin rays articulate with the ventral edge of the

scapulae by various intermediate skeletal elements.

Dorsal fin

ProximalMiddleDistal

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 How do different forms of mortality effect overall population growthgrowth????

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 SystemsFish Circulatory Systems- -

• 2-chambered heart )1 atrium and 1 ventricle• Gills – site of gas exchange

Fish Respiratory System - gillsFish Respiratory System - gills

O2 and CO2 are exchangedAt finely branched gill

filaments supported by gillarches

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