Monitoring fish health
Along with the frequent sampling of some fish to determine their size, the fish can be checked for their health status. Tilapias are very hardy fish and seldom show signs of disease. Good nutrition and good water quality with plenty of dissolved oxygen are key factors in ensuring strong and healthy fish.
Observation of the direct feeding behaviour of the fish gives information about the well-being of the fish as well. If the fish always come to the water surface when the farmer spreads the feed, this is an indication that they feel well. If they do not come during feeding, this could be a hint that something is wrong. In this case, the farmer should stop feeding the fish for one or two days and examine some individual fish. The caught fish than should be checked for ectoparasites and their gills for parasitic worms.
When checking the fish for health, the following criteria should be looked at:
- Good shape and no skinny fish (well-balanced corpulence)
- Eye role reflex when taken out of the water
- No damage to the scales and fins
- No ectoparasites (parasitic crustaceans) on the body surface
- Red gills without parasitic worms
If any health problems are found, action must be taken immediately. Ectoparasites can be treated with salt baths (2 to 3 % salty solution) for 20 minutes. In case of strong mortality in one or many of the ponds, the farmer needs to get help from a microbiological lab to find out the reason. Most likely the fish will need treatment with medicine with the help of a veterinarian.