FOOD ADD AGRICULTURE ORGANIZATION OF THE UNITED NATIONS
Rome, 1974

TABLE OF CONTENTS

This informal report is one of a aeries of reports prepared during the course of the UNDP project identified on the title page. The conclusions and recommendations given in the report are those considered appropriate at the time of its preparation. They may be modified in the light of further knowledge gained at subsequent stages of the project.

The designations employed and the presentation of the material in this document do not imply the expression of any opinion whatsoever on the part of the United Nations or the Food and Agriculture Organization of the United Nations concerning the legal or constitutional status of any country, territory or sea area, or concerning the delimitation of frontiers.

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TABLE OF CONTENTS

SUMMARY

1.     INTRODUCTION

1.1     Origins of the project

1.2     Purpose of the report

2.     AREA AND METHODS OP OBSERVATION

2.1     Background information

2.2     Sampling methods

3.     Tilapia spp. IN THE NIGER DRAINAGE

3.1     Upper Niger and Benue Rivers

3.2     Lower Niger

3.3     Kainji Lake area

3.4     Summary

4.     OBSERVATIONS TAXONOMIC

4.1     Useful literature descriptions of Tilapia

4.2     Nomenclature of Kainji Lake Tilapia

4.3     Fin counts of T. galilaea and T. nilotica

4.4     Separating small T. nilotica and T. galilaea

4.5     Length-weight relationship of T. galilaea

4.6     Standard length-total length relationship of T. galilaea and T. nilotica

4.7     Meristics of T. zillii and T. dageti

5.     LIFE HISTORY NOTES

5.1     Distribution

5.2     Habitat of fry (T. galilaea and T. nilotica)

5.3     Reproduction of T. galilaea and T. nilotica

5.4     Predation on Tilapia

5.5     Food of T .galilaea

6.     RELATIVE POPULATIONS

6.1     Commercial catch

6.2     Gillnet sampling

6.3     Shoreline sampling

6.3.1     Electrofishing

6.3.2     Castnet samples

6.3.3     Dipnet samples

6.4     Summary or relative abundance

7.     GEAR SELECTIVITY FOR T. galilaea

7.1     Gillnets

7.2     Castnets

8.     COMMERCIAL FISHERY ASPECTS

8.1     Fishing methods

8.1.1     Passive gillnetting

8.1.2     Active gillnetting

8.1.3     Castnetting

8.2     Edibility

9.     MANAGEMENT

9.1     Poisoning

9.2     Net mesh-size regulation

9.3     Numbers of fishermen

9.4     Proposed administrative agency

10.   SUMMARY OF RECOMMENDATIONS

Appendix 1     REFERENCES

LIST OF TABLES

1.     Standard length-weight relationship of 506 T. galilaea from Kainji Lake,16 1969–1973

2.     Standard length-average total length of 416 T. galilaea from Kainji Lake, 1970–1973

3.     Standard length-average total length of 95 T. nilotica from Kainji Lake, 1970–1973

4.     Length-frequency distribution of T. galilaea in electro-fishing and dipnet samples from Kainji Lake, 1970–1973

5.     Length-frequency distribution of T. nilotica in electro-fishing and dipnet samples from Kainji Lake, 1970–1973

6.     Estimated abundance of fish appearing in commercial catches on sale at Shagunu on market days, 1971–1973

7.     Length-frequency distribution of T. galilaea in gillnet and castnet catches (stretched mesh) in Kainji Lake

LIST OF FIGURES

1.     Location map of Niger and Benue Rivers and Kainji Lake in Nigeria

2.     Map of Kainji Lake showing sampling locations

3.     Standard length:weight relationship of T. galilaea in Kainji Lake and Volta

4.     Standard length:total length relationship of T. galilaea in Kainji Lake

5.     Standard length:total length relationship of T. nilotica in Kainji Lake

6.     Length frequency distribution of T. galilaea caught in various mesh sizes of gillnets in Kainji Lake (1969 to 1972).