Before you anaesthetise a fish you should check the fish using the checklist below:
- Fish should be viewed in the water (from above and from the side if possible), assessing their movements and respiratory rate. In general, fish movements are fluid and seeming relatively effortless.
- The respiratory movements are generally slow and not obvious. ‘Wooden’ movements, or marked respiratory movements should be viewed with suspicion.
- The skin in general should be smooth and unbroken, haemorrhages may suggest localised scale damage or more serious septicaemic problems.
- The scales should normally lay flat against the body. Lifting of scales to produce a ‘pine-cone’ effect may be due to localised or generalised fluid build up in the skin, or due to abdominal swelling due to ascites (fluid in the belly of the fish).
- During the overall assessment of the condition of the fish including observation of its respiratory action, gills may be glimpsed partially. In the majority of cases it will be necessary to lightly anaesthetise fish to examine the gills in detail. The gill can be seen by gently lifting the operculum and using a suitable light source to illuminate the buccal cavity. The gills should normally be a healthy ‘salmon pink’ colour, with clearly demarcated primary lamellae.
Anaesthetising fish is fairly easy but still isn’t something to be done lightly. Any anaesthetic a carries a risk, sometimes because the animal has an unknown/undiagnosed problem which can cause an issue. For this reason we don't suggest the routine use of anaesthesia of koi carp just to give them a general check-up. However there are lots of instances where anaesthesia is extremely useful, such as:
- handling of valuable fish, or dangerous fish (particularly large fish)
- handling broodstock for stripping, blood sampling, treatment etc.
- vaccination by injection