Distribution and Biology of Chambo (Oreochromis spp.) in Lakes Malawi and Malombe.
A report prepared by the GOM/FAO/UNDP Chambo Fisheries Research Project
MALAWI
| Distribution and Biology of Chambo (Oreochromis spp.) in Lakes Malawi and Malombe. |
FI:DP/MLW/86/013, Field Document 21, July 1992
by
G.F. Turner and N.C. Mwanyama.
For bibliographic purposes this document should be cited as follows:
Turner, G.F. and N.C. Mwanyama. 1992 Distribution and biology of Chambo (Oreochromis spp.) in Lake Malawi and Malombe. GOM/UNDP/FAO Chambo Fisheries Research Project, Malawi. FI:DP/MLW/86/013, Field Document 21: 26p.
This report was prepared during the course of the Chambo Fisheries Research project. The conclusions and recommendations given in the report are those considered appropriate at the time of its preparation.
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 Food and Agriculture Organization of the United Nations concerning the legal or constitutional status of any country or sea area, or concerning the delimination of frontiers.
FOOD AND AGRICULTURE ORGANISATION OF THE UNITED NATIONS
Monkey Bay, Malawi, July 1992
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Distribution and Biology of Chambo (Oreochromis spp.) in Lakes Malawi and Malombe.
4. CHAMBO SYSTEMATICS AND IDENTIFICATION
7. IMPLICATIONS OF BIOLOGY FOR MANAGEMENT OF FISHERIES
Appendix One: Summary of Samples Analysed for Studies on Distribution and Reproductive Biology
LIST OF CHAMBO FISHERIES RESEARCH REPORTS
The biology of the three chambo species, Oreochromis karongae, O.lidole and O.squamipinnis was studied in the course of a year-long stratified sampling programme involving all artisanal and industrial fishing gears. No justification could be found for the separation of O.saka from O.karongae. Identification of adult male chambo was relatively straightforward. In Lake Malombe, females and non-breeding males of O.karongae and O.squamipinnis could not be reliably distinguished.
Although concern has been expressed that seining or trawling on nesting areas could be detrimental to chambo stocks, this seems unlikely, as catches consist mostly of males which play no part in parental care, and are able to mate with a large number of females during the course of a breeding season. Fry-guarding females and small juveniles are vulnerable to seining in shallow water nursery areas where fry are guarded and released. Chambo have longer breeding seasons than was previously believed, with low reproductive activity only during the months of May to July, at which time large numbers of juveniles are present in shallow water. Thus, there is no biological justification for a closed season. Oreochromis lidole has considerably lower fecundity than the other species. Females of O.squamipinnis from Lakes Malombe and Malawi differ in their fecundities, while those of O.karongae do not. The size at maturity of chambo in Lake Malombe is not smaller than in Lake Malawi, and so there is no reason for the present regulations in which smaller mesh sizes are permitted in Lake Malombe. Depth preferences of chambo are size-related, and not species-related. Thus, all species are exploited by artisanal, semi-industrial and industrial fisheries, which must be considered to exploit a single stock. Chambo feed mainly on filamentous diatoms in Lake Malawi and on zooplankton and solitary diatoms in Lake Malombe.
Map showing the project's working area and statistical divisions (minor strata).