C8: PAIN, DISTRESS, ANAESTHESIA, HUMANE KILLING IN ZEBRAFISH – LUCIA VERGAUWEN
RECOGNITION OF PAIN, SUFFERING, DISTRESS
HEALTHY FISH
❖ showing normal behavior
o They are just swimming randomly in the tank
o Sometimes a fish follows another fish, this is normal → there is a hierarchy where
the dominant fish follows other fish (but not all the time)
▪ they are not hassling the fish !
❖ Normal density, around 5 zebrafish per liter
❖ during feeding
o They become very active and eat it immediately
o It is normal that some dominant fish get more food
o Make sure you do not only feed them with nice food, but also provide dry food that covers the tank so also the
small fish can eat enough
o Sometimes they accelerate which is a good sign because it triggers their natural hunting behavior
o If fish are remaining at the bottom of the tank and do not react when food is given, there might be a problem !
❖ larvae stage
o Larvae around 25 days old
o The food is all over the tank so that all the fish can find the food, they do not need to swim after it! Important
when they are still young
UNHEALTHY FISH
Behavior
❖ The fish shows a weird swimming pattern
❖ If they become too heavy, they start to lie on the bottom and not swim anymore
❖ The fish is staying at the bottom, but this is not completely abnormal
❖ It cannot swim normally in one direction
❖ Breathing heavily, faster than a normal fish
Morphology
❖ If there is a morphological change, look at the behavior to see if the fish is suffering
❖ The fins are not as open as they should
❖ The fish is a bit too skinny
❖ The female fish is too big, the belly is so big that the spine is starting to curve
o it is probably because the eggs get stuck inside and the eggs cannot be released
o This can lead to coloration of the belly
❖ The belly has a bit of a coloration
❖ There is a malformation of the jaw → there is extra tissue which is not normal
❖ There is a problem with the eyes → very white with a small black dot = blind eye
o Fish have regenerating eyes so the eye could heal !
o It could also live with one eye, it is not always that bad → see whether is suffers from having one functional
eye → If it is fine, you should not kill it
❖ The gills are red, the operculum could be missing (which normally covers the gills)
o They can live with this, but you should look at the behavior to see if it suffers from it → they are more prone to
infections if the gills are exposed
o Sometimes it is because other fish are picking on it, but it could also be a problem with the development
1
RECOGNITION OF PAIN, SUFFERING, DISTRESS
HEALTHY FISH
❖ showing normal behavior
o They are just swimming randomly in the tank
o Sometimes a fish follows another fish, this is normal → there is a hierarchy where
the dominant fish follows other fish (but not all the time)
▪ they are not hassling the fish !
❖ Normal density, around 5 zebrafish per liter
❖ during feeding
o They become very active and eat it immediately
o It is normal that some dominant fish get more food
o Make sure you do not only feed them with nice food, but also provide dry food that covers the tank so also the
small fish can eat enough
o Sometimes they accelerate which is a good sign because it triggers their natural hunting behavior
o If fish are remaining at the bottom of the tank and do not react when food is given, there might be a problem !
❖ larvae stage
o Larvae around 25 days old
o The food is all over the tank so that all the fish can find the food, they do not need to swim after it! Important
when they are still young
UNHEALTHY FISH
Behavior
❖ The fish shows a weird swimming pattern
❖ If they become too heavy, they start to lie on the bottom and not swim anymore
❖ The fish is staying at the bottom, but this is not completely abnormal
❖ It cannot swim normally in one direction
❖ Breathing heavily, faster than a normal fish
Morphology
❖ If there is a morphological change, look at the behavior to see if the fish is suffering
❖ The fins are not as open as they should
❖ The fish is a bit too skinny
❖ The female fish is too big, the belly is so big that the spine is starting to curve
o it is probably because the eggs get stuck inside and the eggs cannot be released
o This can lead to coloration of the belly
❖ The belly has a bit of a coloration
❖ There is a malformation of the jaw → there is extra tissue which is not normal
❖ There is a problem with the eyes → very white with a small black dot = blind eye
o Fish have regenerating eyes so the eye could heal !
o It could also live with one eye, it is not always that bad → see whether is suffers from having one functional
eye → If it is fine, you should not kill it
❖ The gills are red, the operculum could be missing (which normally covers the gills)
o They can live with this, but you should look at the behavior to see if it suffers from it → they are more prone to
infections if the gills are exposed
o Sometimes it is because other fish are picking on it, but it could also be a problem with the development
1
