Fish

Seite 1

Fish 1

Understand how diverse fish are in terms of fish groups, life history, environmental requirements

Diversity

Primitive phylogenetic position

Jawless - rasping disc

Cartilaginous

Bony fish

Distribution

58% bony fish - Marine environments

42%bony fish - Freshwater

Physiologically cope w hot soda lakes (43deg) to sub freezing antarctic (-2deg)

Antifreeze in blood

Life history

Small as 7.5mm

Largest =whale shark = 12+m

Life span <1yr-150yrs

Reproduction

Open water spawning

Spawning in nests

True viviparity

Oviviarity

Internal fertilisation - then egg deposition

Mating systems

Promiscuous

Polygymy

Polyandry

Monogamy

Parental care

None - egg care

Offspring care

Maternal

Paternal

Monogamy

Sexual dimorphism

Absent

Highly developed

Fecundity

1-1000s eggs

Hermaphroditism

Protandrous

Protogynous

Simultaneous

One species fertilises own egg

Asexual reproduction

All female species

Mate with males of other species

Offspring all female

Environmental requirements

Water salinity

Temp = -2-20+

Behaviour

Territorial

Shoaling

Feeding

Surface

Substate

Predators

Herbivores

Planktivores

Species specific

Water quality

pH

Ammonia

Nitrite

Nitrate

Appreciate their importance in a variety of contexts

Ornamental

20-25 mil in tanks

20 mil in ponds

4000 Dif species

£3-4 bil GBP

Koi in ponds

Public aquaria

Handling

Often challenging

Avoid mechanical damage - 2ry infection

Pick up

Stress

Many won't tolerate netting

Venomous / spiny

Experimental models

Aquaculture

Fish vets act as government inspectors

£49 bil

Loss from disease £1.8 bil

Public health

Farmed fish

Salmon farming

Salmon lice infections -14 mil euros

Salmon louse

Brief knowledge of veterinary procedures associated with fish

Health care

Prevention best

Quarantine

30-90d

Check all fish in and out

Health check sample

Examine + dissect mortalities

Disease occurs - prolong

Designated equipment

Disinfection of nets

Routine UV sterilisation

Staff proficient

Prophylaxis?

Disease organisms

Virus

Bacteria

Parasites

Fungi

Safety

Electrocution

Glass tanks

Slips

Drowning

Bites, scratches + stings

Serious + fatal damage possible

Research

Zoonoses

Euthanasia

Ornamental , experimental + aquaculture

UK schedule 1 - Concussion of brain

Striking

Overdose

Concussion followed by destruction of brain b4 return of consciousness

CO2

Painful - esp trouts

Stress

Infections take hold

Caused by sudden change in H2O quality

Monitor!

Seite 2

Fish 3

Recognise external + internal features

NEED plain paper

External

Gills

Pink = problem WQ

Brown = nitrite poisoning

Fins

Eroded = WQ problem

Anal + dorsal fins may have spines

Combination of spines + fin rays

Spines = bony + sharp

Stability

Days soft + flexible

Medial

Dorsal

Up to 3

Prevents rolling

Sexual displays

Rivalry

2nd

Forward thrust

Rays

Caudal

Anal

Stability

Markings

Courtship

Distract predators

Adipose

Lateral - paired

Pelvic

Elevation + descent

Brake

Sharp turns

Pectoral

Adapted to sucker (not all)

Slow

Precise

Braking

Steering

Pitch

Yaw

Rolling

Lateral line

Care!

Primary sense organ

Detects vibrations

Determines direction

Detects changes in pressure

Invaluable - fish in dark

Blood sample

Caudal peduncle

Measuring

Standard

Fin erosion

Fork

Erosion?

Total

Most reliable

Mouth positions

Inferior

Terminal

Sub terminal

Protrusible

Superior

External

Swim bladder

Hollow

Gas filled

Conservation of energy

Maintain neural buoyancy

Species without need to continue swimming or they will sink

Muscles relax = swim bladder Inc = floats up

Muscles tighten =swim bladder dec = hovers weightless

Muscles tighten = swim bladder dec = fish sinks

Scales

Form barrier

Many diff types

Placoid

Raised

Inc speed

Dec drag

Shark

Cycloid

Bony fish

Salmon

Trout

Carp

Smooth edges

Ctenoid

Bony fish

Jagged edges

CT covered w Ca

Mucus layer acts as covering also

Prevent infection

Ganoid + Cosmoid = ancient

See Flash cards

Form + function of fish skeleton, muscle,cardiovascular system, respiration, digestion + urogenital system

Skeleton

Older fish - Bowfin

V ossified skull

Hard to kill w concussion

Pelvic girdle not attached

Non protrusible jaw

Elongated dorsal fin

Carp

Reduced skull

Jaw semi protrusible

Pelvic girdle unattached

Newer fish - Perch

Less ossified skull

Protrusible jaws

Pelvic girdle attached

Need to know

Skull

Backbone

Vertebrae

Change of shape as you run along

Fin rays

Soft

Spiny

Fin ray support

Ribs

Pelvic girdle

Pectoral girdle = fin support

Muscles

Muscle blocks

Driving force

Skeletal

Striated

Smooth

Digestive tract

Swim bladder

Repro tract

Excretory tract

Lens muscle

Cardiac

Stiated

Jawless

Simple striated

No paired appendages / jaws

No septa

Jawed

Epaxial v Hypaxial

Divion on sputum

Myosepta (CT) separates myotomes

Red

Thin lateral

Sustained swimming

Hard to fatigue -slow

Abundant myoglobin + mitochondria

Aerobic

Recover <1hr

White

Short duration

Escape

Quick fatigue

Little myoglobin

Little vascularisation

Large diameter

Long recovery

Anaerobic glycolysis

Circulatory system

V simple

Blood from Gills - Body - Heart - Back to gills

2 chambered heart

Sinus venous

Heart

Atrium

Ventricle

Conus arteriosus

Variation

Lung fish

Blood

Plasma 80% water

Erthrocytes

Flattened

Nucleated

Haemoglobin

Leukocytes

Thrombocytes

Lymph

Gills

Care!

Also allow passage of fluids + minerals

Bony arches

Gill rakes

Gill filaments

Lamella

Allow counter current exchange

Cont ventilation needed

Movement drawing water in

Reverse = cough

Sharks skates + rays use skin flaps to create current

Low Oxygen / high demand

Inc freq of ventilation

Inc ventilatory stroke volume

Accessory ventilation

H20 at suface

Breathe air = gill collapse

Gill modifications

Skin

Gut

Swim bladder modification

Kidney

Filter liquid waste

Regulate H2O + Salt

Osmoregulation

Fresh water

Fish have higher salt content than environment

Active uptake of ions

Excrete lots of dilute urine

Salt water

Fish have lower salt content than evironment

Active secretion of ions

Active drinking

Excretion of highly concentrated urine

Smolting

Transformation allows movement from fresh water to salt water

Stomach + Intestine

Digestion + Absorption

Piscivorous - short intestines

Herbivorous - long intestines

Pyloric caeca

Finger like projections

Junction - Stomach + SI

Secrete enzymes that aid digestion

Liver

Secretes enzymes

Storage of fats + Carbs

Destruction of old blood cells

Maintains blood chemistry

Nitrogen excretion

Urogenital tract

Vary

Primitive fish - kidney + genitals fused

One duct

Advanced fish - Separated ducts

Live birth

Uterus

Oviduct

Male fish

Testes attached to kidney

White lines along kidney

Female

Yellow lines along kidney

Egg filled?

Hagfish + lamprey

Single gonads

No ducts

Release gametes into body cavity

Sharks

Paired gonads

Internal fertilisation

Chimaeras, Bony fishes

Paired

Ext/Int

Sperm released via separate opening

Teleost

Ova in cont. sac from ovary - oviduct

Exceptions - release into body cavity