Preliminary Survey of the Pelagic Fishes of East Africa.
The scope of the survey is defined. A short description is given of the hydrographic and climatic conditions of the East African coastal region. A full description is made of the gear used in multiple trolling from M.F.V. "Research". The efficiency and limitations of the gear are discussed, with suggestions for improvements in the method. Most effective trolling speed was 5-6 knots. The twenty-eight species of fish taken by trolling are fully described. The catch, seasonal abundance and distribution of the pelagic fishes are discussed. Some species - Caranx, Sphyrcena, Aprion and Plectropoma appear to be present throughout the year. They are more numerous during the N.E. monsoon when the gonads are in the spawning condition. Coryphcena hippurus makes an inshore spawning migration from January to June. Due to migrations other pelagics such as the Scombrids show a marked seasonal abundance, but little is known as yet of the reasons for the migrations. Shoals of tunny-like Scombrids have been seen in large numbers but fish were not taken from them by trolling. Monthly details of the catch of fishes are tabulated for each section of the coast. The average catch rate for the whole of the survey was 1•14Ibs./line/hour. The monsoon conditions have a direct bearing on the productivity of the fishery, especially in the S.E. monsoon. Fish are almost entirely restricted to within the 100 fin. line. Largest numbers are taken where a shallow shelf extends out from the fringing reef or over the shallow off-shore banks. Reasons for this distribution are advanced. It is concluded that multiple trolling alone by a fishing boat the size of "Research',' would not be commercially profitable. However the expansion of the native fishery for pelagic fishes is advocated. Two possible methods of development by using trolling are given. Suggestions are made for the capture of tunny-like shoals by means of a purse seine or the live bait technique, together with the use of deep long lines for tunny and gill nets for the capture of the smaller shoaling Carangids and Scomberomorids. The future biological investigations to be carried on the pelagic fishes are discussed.
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| Format: | Report biblioteca |
| Language: | English |
| Published: |
Her Majesty's Stationary Office
1956
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| Subjects: | Fishery surveys, Pelagic fisheries, Hydrographic surveys, Climatic data, |
| Online Access: | http://hdl.handle.net/1834/7875 |
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