Harvesting and handling of the fish
When harvesting fish, we always must keep in mind that they are—like all other vertebrates—animals that experience pain and fear if they are mistreated. Thus the fish need to be handled with care and respect, especially in the context of organic farming, and harvesting must be done as gently as possible.
A seine net, which is pulled by two persons along the complete pond, is one of the best solutions for harvesting larger numbers of fish and causes little stress and panic among the fish. If the water level of the pond can be lowered, this makes the job for the fish farmer easier. If the pond can be emptied to a harvesting depression near the outlet, the fish can be caught using a scoop net. When the fish realize, however, that their space to move around in is getting continuously smaller, they inevitably panic. This means that quick action is required.
If there is much fish, harvesting the fish out of the filled seine net or out from the harvesting channel with the help of a scoop net should be done by several people simultaneously. From the pond, the fish must be transferred to a clear water tank or to a transport tank in case they shall be transported to a slaughterhouse.
If it is not intended to transfer the fish alive to another place, the fish must be killed immediately after being taken out of the water with the scoop net. It is unacceptable to let the fish die slowly outside the water by suffocation. The best way to kill small and medium numbers of fish is to strike them by a blow on the head using a beating wood.
If ice is available to make water/ice-slurry, then bigger numbers of fish can be transferred at once into a prepared tank. To prepare the slurry, one part crushed iced is mixed with one or two parts water. The ice should not melt completely. When the fish are transferred from the pond water (~30 °C) to the ice slurry (~0
°C) they will be anaesthetised almost immediately. But as they are not yet dead, they must be killed by a gill cut to let them bleed out.
FiBL (2011): African Organic Agriculture Training Manual. Version 1.0 June 2011. Edited by Gilles Weidmann and Lukas Kilcher. Research Institute of Organic Agriculture FiBL, Frick