The Different Types of Freshwater Fish culture and Polyculture
The different fish farming production systems are generally distinguished according to their degree of intensification which is itself usually defined according to the feeding practices as food represents more than 50% of the total operating costs in intensive systems.
However, intensification (or, inversely, extensification) involves many other production factors, such as water, land, capital, and labor.
A first classification could be established as follows:
• Extensive fish farming production systems are based on the use of natural feed produced in the fish culture structure/environment without any input with a very low input level. Rice-fish farming systems can be considered as belonging to this extensive level as fish takes benefit of inputs added for rice cultivation
• Semi-intensive fish farming systems rely on the use of fertilization (organic and/or mineral) to produce natural feed and/or supplementary feed, but with a significant amount of the fish diet supplied by natural feed.
Integrated crop-livestock-fish farming systems are typically belonging to this type of fish culture as well as all fish farming systems recycling various types of wastes including direct excreta reuse systems (latrine ponds of Vietnam for example) and indirect sewerage systems. Both systems provide high fish yields
• Intensive and super intensive systems have all the fish nutritional requirements provided by a nutritionally complete pelleted feed with little or no nutritional benefits from natural productivity of the pond or water body where fish culture is achieved (lake, river). The feed used in these fish farming systems are generally rich in proteins (25 to 40%) and are then costly.
The main facilities used for this type of fish farming are pens, cages or raceways with a very high water renewal rate (natural through water currents of artificial through pumping) The different types of fish farming systems according to the level of intensification are summarized in Table 1.
Table 1. Different levels of intensification of fish farming systems.
An interesting transition between semi-intensive pond fish culture and super-intensive fish culture systems is given by tilapia floating cage culture in productive natural water bodies such as lakes in the Philippines. The stocking rate of tilapia fingerlings is adapted to the cage size, the natural productivity of the water and the culture management.
At low stocking densities (up to 25 fish.m-2), supplemental feeding may not be necessary especially in productive lakes during the abundant plankton season. To accelerate fish growth during the low productive months, supplemental feeding is applied at rates of 3 to 5% of body weight per day (see Table 2).
Table 2. Stocking rates for Nile tilapia in cages of different sizes and management schemes.
Another typology of fish farming production systems can be proposed, based only on the discrimination between systems where the feeds originate only (or mostly) from the ecosystem (endogenous feeds produced by the ecosystem) and systems where feeds are entirely exogenous and where fish feeding is entirely based on pelleted feeds or even trash fish.
Management of the first type involves fertilization and/or supplementary feeding, polyculture practices and there is a very strong interaction between stocking rate, final individual weight of fish (growth rate) and yield, which have to be managed very thoroughly. Management of the second type relies mainly on monoculture, high stocking rates and artificial feeding with a high protein feed.
Authors:
Lionel Dabbadie and Jerome Lazard
