Development of new artificial microdiets for onfeeding of fish larvae
Most teleost fish species have external fertilization. The fertilized eggs develop in water and the larvae hatch out of the egg in an early development stage. Newly hatched larvae have a yolk sac which is initially used as food source (=yolk sac phase). This yolk sac phase takes between one day and several weeks depending on the fish species. When the yolk sac has been consumed, larvae must take up food. This phase is considered as critical as food in adequate size and composition must be available in sufficient quantities. If suitable food is not available the larvae die due to starvation. If food is available but does not contain the essential components and nutrients the larvae do not die immediately but during the course of development due to malnourishment.
In nature fish larvae feed mainly on zooplankton. Also for on-feeding of fish larvae in aquaculture and in ornamental fish culture live food is used today, as e.g. algae, rotifers, or artemia. Only the larvae of few species can be fed with artificial microdiets.
Artificial microdiets have advantages: (1) They are of uniform quality and continuously available. (2) They can be adjusted to the requirements of different fish species. (3) They are free from pathogens and parasites. (4) They can be supplemented with drugs in case of fish diseases.
In our research project we develop artificial microdiets for the larvae of fresh water fish species which have commercial importance in aquaculture. In the course of the project the most successful food type was also tested on larvae of the following ornamental fish species. Nimbochromis venustus, Otopharynx sp., Hemichromis lifalili, Poecilia reticulata, Danio rerio, Ancistrus sp. and Corydoras sp.. For onfeeding of larvae we used exclusively artificial microdiet food and no live food. When the fish had a size of 0.8 – 1.0 mm the food was changed to standard aquarium food. The survival rates were in a range of 75 – 98%, the growth rates similar to those with live food.