Lecture - Aquaculture and Fisheries Center

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