Fish Welfare, Stress Indicators, and Water Quality Management in Aquaculture

Besides benefiting fish, what is a tangible benefit of good fish welfare?

Better consumer perception and industry reputation

Why do some researchers think fish do not feel pain?

They lack certain brain structures and have fewer C-type pain receptors

What is considered a short-term starve?

24-48 hours

Why are fish placed on a short-term starve?

To empty the gut before handling and reduce stress/water quality issues

What is considered a long-term starve?

Greater than 3 days

What are effects of ammonia exposure on fish?

Gill damage, stress, poor growth, increased disease susceptibility, death at high levels

Name two actions to reduce unionized ammonia.

Reduce feeding, lower temperature, lower pH, increase biofilter oxygen, water exchange

What disease does nitrite cause?

Brown blood disease

What is the ideal nitrite concentration?

Zero

What are two sources of CO₂ in aquaculture systems?

Fish respiration and biofilter bacteria

Name two welfare concerns associated with high CO₂.

Cataracts, kidney damage, decreased pH

How is CO₂ removed from a RAS?

Degassing and proper stocking density

What happens to dissolved oxygen as temperature increases?

Oxygen solubility decreases

Which gas is most concerning for supersaturation?

Nitrogen (N₂)

At what level can nitrogen supersaturation become lethal?

Above ~104%

What is a quick mitigation for gas supersaturation?

Degassing or increasing oxygen

What problems are caused by low water velocity?

Low DO, waste buildup, poor muscle tone

What should facilities implement to ensure good staff welfare practices?

Training, SOPs, regular review, and clear reporting structure