Mechanised Fisheries of Lake Malawi
Species composition analysis was used to determine the relationships between the different mechanised fisheries and between these and other techniques. All chambo species were found to be heavily exploited by both mechanised and artisanal sectors, indicating that a single assessment of chambo fisheries is required for the south-east arm of Lake Malawi. The midwater trawl was found to catch, in addition to chambo, large quantities of small pelagic haplochromine cichlids. The bottom trawl and pair trawl fisheries were found to be largely dependent on two separate communities of demersal haplochromine cichlids. Thus, all three major trawling techniques can be assessed separately. The topography of the various commercial fishing license areas is considered, and it is concluded that for the purposes of stock assessment that four areas be considered as independent units: Area A, Areas B & C, Areas D, E, & F and Area G.
The midwater trawl haplochromine fishery is estimated to be fully exploited in the south-east arm. The bottom trawl fishery in the south-east arm has been overexploited since 1983 and is presently yielding less than half of its potential. It was found that pair trawl fisheries did not show significant relationships between catch and effort, and it was not possible to estimate the maximum sustainable yields or optimum fishing levels. Possible explanations are discussed. The pair trawl fishery in Area A is presently showing signs of dangerous instability.