Polyculture - A culture practice to utilize all ecological niches of pond ecosystem effectively

Prabjeet Singh¹, Sajid Maqsood², M.H.Samoon³, Nitin Verma¹,Shashank Singh¹ & Amita Saxena¹

¹College of fisheries, G.B.Pant University of Agriculture and Technology, Pantnagar, Uttrakhand, India.

²Department of food technology, Faculty of Agro-Industry, Prince of Songkla, University Thailand.

³Faculty of Fisheries, SKUAST-K, India.

Corresponding author E-mail: prabjeet29255@yahoo.co.in

Polyculture is the practice of culturing more than one species of aquatic organism in the same pond. The motivating principle is that fish production in ponds may be maximized by raising a combination of species having different food habits. The concept of polyculture of fish is based on the concept of total utilization of different trophic and spatial niches of a pond in order to obtain maximum fish production per unit area. The mixture of fish gives better utilization of available natural food produced in a pond. The compatible fish species having complimentary feeding habits are stocked so that all the ecological niches of pond ecosystem are effectively utilised. Polyculture began in China more than 1000 years ago. The practice has spread throughout Southeast Asia, and into other parts of the world.

The possibilities of increasing fish production per unit area, through polyculture, is considerable, when compared with monoculture system of fish. Different species combination in polyculture system effectively contribute also to improve the pond environment. Algal blooming is common in most tropical manure fed ponds. By stocking phytoplanktophagus Silver carp in appropriate density certain algal blooming can be controlled. Grass carp on the other hand keeps the macrophyte abundance under control due to its macrovegetation feeding habit and it adds increased amount of partially digested excreta which becomes the feed for the bottom dweller coprofagous common carp. The bottom dwelling mrigal, common/mirror carp help re-suspension of bottom nutrients to water while stirring the bottom mud in search of food. Such an exercise of bottom dwellers also aerates the bottom sediment. All these facts suggest that polyculture is the most suitable proposition for fish culture in undrainable tropical ponds.

HOW DOES POLYCULTURE WORK?

Ponds that have been enriched through chemical fertilization, manuring or feeding practices contain abundant natural fish food organisms living at different depths and locations in the water column. Most fish feed predominantly on selected groups of these organisms. Polyculture should combine fish having different feeding habits in proportions that effectively utilize these natural foods (Figure 1). As a result, higher yields are obtained. Efficient Polyculture systems in tropical climates may produce up to 8,000 kg of fish per hectare per year.

Figure 1: Polyculture utilizes natural foods efficiently

FISH USED IN POLYCULTURE

Combinations of three Chinese carps (bighead, silver and grass carp) and the common carp are most common in Polyculture. Other species may also be used. While fish may be grouped into broad categories based on their feeding habits, some overlap does occur. In our state Polyculture systems has tremendous potential and our endemic Schizothoracid species can be utilized effectively in composite fish culture .

FACTORS AFFECTING SPECIES SELECTION AND STOCKING RATES

1. Water temperature.

2. Market value of fish.

3. Pond fertilization practices.

4. Feeding habits of fish.

5. Feeding habits of fish.

6. Potential of uncontrolled spawning in grow-out ponds.

STOCKING RATES FOR POLYCULTURE SYSTEMS

Examples of stocking rates for Polyculture systems used in various countries are presented in Table 1, Modification to suit conditions in other locations may be necessary.
Table 1: Number of fish stocked per 100 m² of pond surface area in Polyculture systems used in various countries.

Potential Problems in Polyculture

Polyculture is an effective way to maximize benefit from available natural food in a pond. But, pond management becomes more difficult when stocking fish species having specialized feeding habits in the same pond because good fertilization and feeding practices must be followed. If inadequate fingerling supply severely limits the choice of species available for polyculture, at least one species should have general rather than specialized feeding behaviour. This will allow more of the available natural food to be utilized.

References

FRI, 1991. Manual on Integrated Chicken-cum-Fish culture, Extension Material Series No. 7, Director, Fisheries Research Institute, Mymensingh: 16pp.

Kumar, D. Manual of fish culture in undrainable ponds. FAO publication..

NACA, 1989. Integrated Fish Farming in China. NACA Technical Manual 7. p.227.

New, M.B. 1987. Feed and Feeding of Fish and Shrimp, ADCP/REP/87/26, FAO/UNDP, 275pp.

Rahman,A.K.A. 1989. Freshwater Fishes of Bangladesh, Zoological Society of Bangladesh, Dhaka: 364pp