CoverKAINJI LAKE RESEARCH PROJECT
FI:SF/NIR 24
Technical Report 3
NIGERIA
PELAGIC PRIMARY PRODUCTION IN KAINJI LAKE
based on the work of
S. G. Karlman

UNITED NATIONS DEVELOPMENT PROGRAMME

FOOD AND AGRICULTURE ORGANIZATION OF THE UNITED NATIONS
Rome, 1973

TABLE OF CONTENTS



Report prepared for
the Government of Nigeria
by
the Food and Agriculture Organization of the United Nations
acting as executing agency for
the United Nations Development Programme

FAO. Kainji Lake Research Project. Nigeria. Pelagic primary production in Kainji Lake, based on the work of 3. G. Karlman.
Rome, 1973. 59 pages, 23 figures,
FI:SF/nir 24, Technical Report 3.

ABSTRACT

As part of the Kainji Lake Research Project being carried out by the Government of Nigeria with the assistance of the United Nations Development Programme and the Food and Agriculture Organization of the United Nations, the pelagic primary production in the lake was studied from December 1970 to September 1972. Production per volume of water and per unit surface area was estimated using the oxygen light and dark bottle technique. Seasonal variations in solar radiation transparency, temperature and composition of subsurface light were also measured. The average production was found to be 822 mg C/m2/d. The transparency and the nutrient content of the water are the main factors limiting photosynthetic production. The phytoplankton production in Kainji Lake has been compared with production in other tropical waters and an attempt has been made to relate the pelagic primary production to fish production. The results indicate an order of magnitude of fish catch for Kainji Lake of 15 kg/ha/a, assuming that 20% of the total production of fish is harvestable. This estimate, while of no higher accuracy than other estimates that have been given, is the lowest so far proposed.

The Food and Agriculture Organization is greatly indebted to the following organizations and individuals who assisted in the implementation of the project by providing information, advice and facilities:

The Government of Finland

The National Advisory Committee for the Kainji Lake Research Project

The Director, Federal Fisheries Service

The hydrologist and officials of the National Electricity and Power Authority

The Fishery Officers of the Ministries of Agriculture and Natural Resources, Kwara and Northwestern State

The Sole Administrator, New Bussa

The Emir of Borgu.


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TABLE OF CONTENTS

Chapter 1   INTRODUCTION

1.1     Kainji Lake

1.2     Climate

1.3     Hydrology

1.4     Limnology

1.5     Geology

1.6     Vegetation

1.7     Land Utilisation

1.8     Engineering Works

1.9     Human Influence

Chapter 2   METHODS

2.1     Sampling Stations

2.2     Measurements and Calculations

Chapter 3   RESULTS

3.1     Estimation of Daily Production

3.2     Production per Surface Area, ΣP

3.3     Production per Unit Volume of Water, P Max

3.4     Annual Production

3.5     Respiration

3.6     Utilisation of Solar Radiation

3.7     Replenishment Rate of Lake Water

3.8     Light Transmission

3.9     Spectrum of Subsurface Light

3.10   Calculation of Production

3.11   Turnover Bate of Plankton Biomass

3.12   Vertical Distribution of Phytoplankton

Chapter 4.   DISCUSSION

4.1     Primary Production in Tropical Lakes

4.2     Comparison of Kainji with Other Tropical Lakes

4.3     Factors Affecting Production

4.4     Fish Production Potential

4.5     Future Development

Chapter 5   CONCLUSIONS AND RECOMMENDATIONS

5.1     Conclusions

5.2     Recommendations

Appendix   BIBLIOGRAPHY

LIST OF TABLES

1.Lake level, volume and area
2.Dam construction
3.Some photosynthetic characteristics of the measurements
4.Weekly data for solar radiation at project site, New Bussa
5.Efficiency of utilisation of solar radiation
6.Data of primary production in some tropical and subtropical lakes and ponds

LIST OF FIGURES

1.Map of Kainji Lake
2.Kainji Lake, rainfall pattern
3.Lake level and Niger inflow at Kowara, 1971–72
4.Submarine photometer - transmission curves for filters
5.Hourly gross increase in oxygen
6 and 7.Daily production per unit area, ΣP and corresponding secchi disc transparency
8.Relation between secchi disc transparency and photosynthetic production per unit area
9, 10 and 11.Depth distribution of photosynthetic rates per unit volume of water
12 and 13.Seasonal variations of the maximum rates, P max, of photosynthesis
14 and 15.Seasonal changes in depth distribution of photosynthetic rates
16.Solar radiation in Kainji, 1971–72
17.Seasonal changes in spectral composition of subsurface light
18.Relation between production per unit area measured in situ and calculated production
19.Relation between secchi disc transparency and depth of the 1%transmission level of the most penetrating component in the spectrum
20.Vertical distribution of photosynthetically active plankton during stratification
21.Range of primary production in a tropical lake
22.Relation between primary production and mean depth
23.Relation between the morpho-edaphic index and primary production