10. CONCLUSIONS

1. A routine environmental monitoring system involving 31 quantifiable parameters has been developed with the necessary field instruments or tools which have been fabricated at FARTC. Six research workers have been trained to undertake environmental monitoring of undrainable fish ponds. Further, a survey programme on 32 rural fish ponds scattered in Cuttack and Puri districts has been completed with this monitoring system.

2. In order to carry out relevant investigations pertaining to chemical biochemical and bacterial aspects of pond productivity, 17 microbiological and 14 biochemical methods and procedures were adopted and initiated at FARTC. However, investigations on nitrogen fixation, nitrification and denitrification would be initiated when proper equipment - accessories for gaschromatograph, liquid scintillation counter, etc. - are obtained and installed.

3. As a result of the environmental monitoring survey on 32 fish ponds and the more detailed microbiological and biochemical investigations on the selected representative pond, it appears that although the water column of these undrainable rural ponds has a very high production potential, under the present given climatic condition it is infertile due to the overall nutrient deficiency with a very pronounced nitrogen limitation.

   At the same time, the sediments have a very large amount of organic and inorganic nutrients almost locked in and unutilized due to the anaerobic nature brought about by the very limited nutrient and oxygen transport within the water column and at the sediment water interface.

4. This basic phenomenon in the fish ponds determines the small resources of the natural fish food organisms. The sediment contains practically no aminals as natural food for benthophagous fish species. The only organisms which can flourish under these circumstances are the blue-green algal species of Microcystis which are able to utilize the rich nutrients of the sediment.

5. However, to confirm these findings a year-long investigation needs to be initiated and the data then analysed so as to develop a suitable fish culture technology for such undrainable ponds by improving the nutrient and oxygen transport between the water column and sediment by means of biological, manual or mechanical tools.

6. Therefore, the following research projects need to be undertaken at FARTC:

   1. Studies on pond productivity along with microbiological and biochemical investigation of the nitrogen and oxygen cycles in old undrainable ponds.

   2. Studies to evolve suitable methods for the transport mechanism and recycling of the sediment-locked nutrients into fish growth.

   3. Studies on the production of non-drainable and drainable ponds under different management techniques.

Table 1
DATA EVALUATION SHEET FOR PERENNIAL POND

1. Pond code

2. Water area, ha

3. Age, year

4. Management

5. Visual colour

6. Transparency, cm

7. Water depth, cm

8. Soft sediment depth, cm

9. Solid sediment depth, cm

10. Sediment gases, dm³m^-2

11. Sediment organic -C, mg g^-1

12. Sediment detritus, g m^-2

13. pH

14. Alkalinity, mg dm^-3

15. NH₄^-N, μg dm^-3

16. NO₃^-N, μg dm^-3

17. PO₄^-P, μg dm^-3

18. Dawn oxygen, mg dm^-3

19. Bacterioplankton, 10⁶ cm^-3

20. Phytoplankton, cell dm^-3

21. Seston detritus, particles cm^-3

22. Seston 60 μm, wet weight

23. Dominant species 60 μm

24. Seston 150 μm, wet weight

25. Dominant species 150 μm

26. Macrozoobenthos 400 μm, m^-2

27. Dominant species 400 μm

28. Macrotecton 400 μm, m^-2

29. Dominant species 400 μm

30. Macrophyte cover, %

31. Dominant species

Table 2
MAIN GROUPS OF BACTERIA TAKING PART IN THE MINERALIZATION PROCESS IN THE POND

Carbon Cycle

1. Oligocarbophilic bacteria

2. Aerobic cellulose decomposers

3. Anaerobic cellulose decomposers

4. Methane producers

5. Hydrogen producers

6. Methane oxidizers

7. Hydrogen oxidizers

Nitrogen Cycle

8. Ammonifyers

9. Aerobic nitrogen fixers

10. Anaerobic nitrogen fixers

11. Nitrifyers

12. Denitrifyers

13. Urea decomposers

Phosphorous Cycle

14. Organic phosphorous decomposers

15. Inorganic precipitated phosphorous decomposers

Sulphur Cycle

16. Hydrogen sulphide producers from protein

17. Sulphate reducers

Table 3
MAIN CHARACTERISTICS OF THE SURVEYED RURAL PERENNIAL PONDS USED FOR FISH CULTURE

Table 4
CONSTRUCTION, BANK RECONSTRUCTION, SEDIMENT EXCAVATION AND MACROPHYTE REMOVAL IN SURVEYED FISH PONDS

Table 5
PLANKTONIC FISH FOOD COMPARTMENTS

Table 6
DOMINANT GROUPS OF ORGANISMS IN PHYTOPLANKTON,
ZOOPLANKTON, ZOOBENTHOS AND ZOOTECTON COMMUNITIES

Table 7
SEDIMENT FISH FOOD COMPARTMENTS

Table 8
DECOMPOSITION OF WATER HYACINTH AND CELLULOSE IN THE WATER AND SEDIMENT LAYERS OF POND 1

Table 9
BACTERIAL POPULATIONS REQUIRING VARIOUS CONCENTRATIONS OF ORGANIC MATTER IN THE WATER AND SEDIMENT OF POND 1 IN FEBRUARY 1983

Table 10
BACTERIAL POPULATIONS INVOLVED IN THE CARBON CYCLE IN THE WATER AND SEDIMENT OF POND 1 IN FEBRUARY 1983

Table 11
BACTERIAL POPULATIONS INVOLVED IN THE NITROGEN CYCLE
IN THE WATER AND SEDIMENT OF POND 1 IN FEBRUARY 1983

Table 12
BACTERIAL POPULATIONS TAKING PART IN THE DISSOLUTION OF PRECIPITATED INORGANIC PHOSPHATE AND IN THE PROTEIN DECOMPOSITION WITH SULPHIDE PRODUCTION IN THE WATER AND SEDIMENT OF POND 1 IN FEBRUARY 1983

Table 13
VERTICAL DISTRIBUTION OF PROTEIN DECOMPOSERS PRODUCING SULPHIDE AND METHANE-PRODUCING BACTERIAL POPULATIONS IN THE SEDIMENT OF POND 1 IN FEBRUARY 1983, × 10³ g^-1 WET WEIGHT

Table 14
CHEMICAL ENVIRONMENT AND INORGANIC PLANT NUTRIENTS IN THE WATER OF UNDRAINABLE PONDS DURING JANUARY 1983

Table 15
CHEMICAL ENVIRONMENT AND NUTRIENTS IN THE SEDIMENT LAYERS OF OLD UNDRAINABLE POND 1

Table 16
DIEL CHANGE OF INORGANIC NUTRIENTS IN THE WATER LAYERS OF POND 1 ON 10 MARCH 1983, μg dm^-3

Table 17
DIEL CHANGE OF OXYGEN CONCENTRATION IN THE
WATER LAYERS OF POND 1, mg dm^-3

Table 18
DIEL CHANGE OF TEMPERATURE IN THE WATER LAYERS OF POND 1, °C