Lecture - Aquaculture and Fisheries Center

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Osmoregulation
Immunity
Stress
and Disease
HK
Adrenalin
Brain
Nerve
Cardinal
Vein
Chromaffin
Cells
Head Kidney
The Beneficial effects of
epinephrine/adrenaline
are…
Better “fight
or flight”
capabilities
• Increases heart rate
• Increases breathing
(respiration) rate
• Opens gill circulatory
system
• Open muscle circulation
• Decreases blood to guts
• Releases sugar from liver
There is no
such thing
as a free
lunch !
Gill Anatomy
Afferent
Artery
Efferent Artery
Cartilage
Rod
Lamella
Afferent
Artery
Efferent
Artery
Freshwater
Fish
Water
Salt
Saltwater
Bony Fish
Water
Salt
Saltwater
Shark
Water
Salt
=Trimethylamine oxide (TMO)
and Urea
Epinephrine makes all
osmoregulatory problems
worse
• FW fish gain more water and
loose more salt
• Saltwater fish gain more salt
and loose more water
• Sharks gain more salt
• Hagfish.. well…they stay
hagfish!
• Starvation
• Entrapment
• Injury
• Social
problems
Brain
HK
Cortisol
ACTH
Adrenocorticotropic Hormone
Interrenal
Cells
Good Effects of
Cortisol ?
•Protein
catabolism
–Breaks down
protein for energy
There is no
such thing
as a free
lunch !
Complement
molecules begin
to assemble a
complex on the
wall of a
bacterium
Complement
finishes forming a
channel through
the bacterial cell
wall.
Lysozyme
•Dissolves
bacterial cell
walls
•Found in
–Blood
–Mucus
–(tears)
Antibodies bind all over a Rhabdovirus
and block it from infecting a cell.
Antibodies recognize foreign antigens on an
“ich” parasite and mark it for destruction.
Uh-Oh!
• Some proteins are really important !
– Antibodies: kill things, flag things for
destruction
– Lysozyme: dissolves bacterial cell walls
– Complement: pokes holes in bacteria,
flags things for destruction
• Macrophages: need those flags
• Neutrophils: need those flags
• Eosinophils: need those flags
Cortisol
Downsides
• Cortisol triggers catabolism of
immune system proteins
• Cortisol saves scarce resources
by reducing expenditures on
immunity
– Less white blood cells
– Less production of immune proteins
Epinephrine: Makes
osmoregulatory
problems worse
Cortisol: Screws
up the immune
system
The
Case
• Bluegills
harvested in
July
• 75-95% die
from
columnaris
infections
The Problem
• When fish are loaded onto the
trucks and into raceways,
they perceive it as lifethreatening
• They make cortisol and
epinephrine
• Osmoregulation problems
• Immunity problems
• No treatment
– 95% die
• Gentle harvest
– 90 % die
• Add salt
– 85% die
• Add penicillin
– 5% die
The
Cure
The Case
• Threadfin
shad are
harvested
and loaded
on trucks
• 100 % die
within 1 hr
The Problem
• When threadfin shad are
loaded onto the trucks,
they perceive it as lifethreatening
• They make epinephrine
• Osmoregulation problems
The Cure
• No treatment
– 100 % die
• Gentle harvest
– 100 % die
• Add salt
– 95 % die
• Add antibiotic
– 95% die
The Case
• Catfish
develop
ulcers and die
3-7 days after
delivery
• Cultures show
common soil
bacteria
The Problem
• Stress triggered cortisol
production
• Cortisol screwed up the
immune system
• The fish became
susceptible to bacterial
infection
What was the stress?
• Normal fish: 1,000,000 bacteria
required to cause infection
• Oxygen depleted fish: only 100
• The neat part: It turns out that
the fish truck had an oxygen
accident!
• Bacteria levels were probably
high in the pond
The Cure
The
Case
• Catfish look normal in
aquariums
• Turn rigid if handled
• Much worse if fish
aren’t feeding
The Problem
•Stress triggered
epinephrine release
•The fish had
osmoregulatory
problems
Why is it a
problem here?
•Very low mineral
levels in the water
•Minerals from the
feed are needed
The Cure
The same thing happens with
grass carp:
They are tough in hard water
but
Fragile in soft water
Many common procedures used
in aquaculture and fisheries are
perceived by fish as life
threatening, but really aren’t
• Hauling in trucks
• Seining
• Weighing
• Holding in tanks
• Aerator noise…
If the fish make a bunch of
epinephrine or cortisol, they
suffer the ill effects, but get
no benefit.
The answer is to
1. reduce their perception of
danger, calm them with
tranquilizers (if appropriate)
2. deal with the side effects using
salt manipulation and antibiotics
if appropriate
If conditions really are
life threatening…
• Rapid temperature
changes
• Poor water quality
• Handling injuries
• Disease
Then, the hormones and
their effects are vital to
fish survival…
But, you must
1.help the fish deal with
the negative side effects
2.try to reduce improve the
dangerous situation
Cures
• Epinephrine
– Gentle handling
– Salt adjustment for
osmoregulation
– Tranquilizers1 for open water fish
• Cortisol
– Gentle handling and holding
– Antibiotics1 for immune problems
1. Use only if required, safe, and LEGAL
Problem - Solution
• Epinephrine
• Epinephrine
– great for fight
– Gentle handling
and flight
– Salt adjustment for
– screws up
osmoregulation
osmoregulation
– Tranquilizers for
• Cortisol
open water fish
– great to provide
• Cortisol
energy in long
lasting
– Gentle handling
emergencies
– Antibiotics for
– screws up the
immune problems
immune system
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