• Notes on the mangrove swamps of Kenya.

      Graham, R.M. (1929)
      It is estimated that the Mangrove Swamps in Kenya cover an area of about 180 squares miles. All have been gazetted as forest reserves. Since only four creek systems have been surveyed, it is obvious that the area given is only approximate, but the composition of the gazetted areas does not vary very much. Judging by the four swamps that have been surveyed, it seems probably that only about two-thirds of the total area can be classed us merchantable forest. The remainder consists of scrub mchu, liIana and undersized mkandaa. Of the merchantable forest, probably 70% consists of well-grown mkoko, with scattered muia and mkandaa, and 30% of badly-shaped mkandaa which, however, finds a market as fuel.
    • Scientific results of the Cambridge Expedition to the East African Lakes, 1930-1: 8. Hydracarina.

      Lundblad, O. (1932)
      This interesting little species does not fit well into any of the subgenera hitherto established, the frontal shield being differently shaped according to sex. In this respect the species resembles somewhat H . mertoni Walt. from the Aru Islands.
    • Scientific results of the Cambridge Expedition to the East African Lakes, 1930-1: 1. General introduction and station list.

      Worthington, E. (1932)
      The Cambridge Expedition to thc East African lakes was orgnnised in 1930 to continue limnological investigations in Kenya, and Uganda. The early African lake expeditions at the beginning of the century concentrated on Lake Tanganyika, but made collections of the fauna and flora of Lakes Victoria, Edward, Albert, etc., and other collections have been brought to European museums by individual collectors. A summary of knowledge up to date was given by Dr. Cunnington (1921), but since that time the sciences of limnology and ecology -have undergone considerable development and we are now able to approach the problems from a somewhat different standpoint,considering the animals and plants in relation to their physical and biological environments, and attacking problems of geographic distribution with a sounder backing from geology.
    • Scientific results of the Cambridge Expedition to the East African Lakes, 1930-1.- No. 16. The smaller Crustacea.

      Lowndes, A.G. (1936)
      The following paper represents the result of the identification of the species of Cladocera, Copepoda, and Ostracoda.
    • The Biology of Trout in Kenya Colony.

      Van Someren, Vernon D. (River Research CentreKenya, 1950)
      Apart from Copley's papers (1940 a, b, 1947, 1950), there have been no scientific observations made on trout biology in East Africa, though van Someren has also published a few preliminary observations (1946). Trout were first introduced into Kenya Colony in 1905, and there are now many miles of trout water available in the Colony; the history of their introduction has been described by Copley (1938, 1940 a and b). Management of these trout waters has been largely empirical and remarkably successful, though the need has now been recognised to support such management policies by biological data. Because such data are largely lacking, the work at the Research Centre, which has gradually increased in scope as facilities became available, has been directed mainly towards the collection and assessment of facts on the natural history of our exotic trout in all aspects. Two and a half year's work has seen the amassing of a very large quantity of such factual data, and the results are presented herewith. The reader will find this first account of trout biology purely descriptive and analytical; very few experimental results are described, and there are only occasional references to aspects and policies of fishery management. Proposals for the later can only be based on the scientific data now being made available, and will follow naturally as results become known and confirmed by experimental procedure. Thus in time will the rivers yield the fullest of which they are capable.
    • Annual report of the East African Fisheries Research Organization, 1952.

      East African Fisheries Research Organization (East African Fisheries Research Organization (EAFRO)Jinja, Uganda, 1952)
      The scientific activity of the former East African Fisheries Research Organization is briefly reviewed. The research refers to the Lake Victoria region.
    • Geology of the Mombasa-Kwale Area Degree Sheet 69 with A Chapter on hte Alkaline Igneous Complex at Jombo.

      Caswell, P.V.; Baker, B.H. (Government Printing OfficeNairobi, Kenya, 1953)
      This report describes an area of some 1,750 square miles lying in the extreme south-eastern corner of Kenya; the area is bounded by latitude 4' S, longitude 39' E, the Kenya-Tanganyika border, and the Indian Ocean. The rocks exposed consist of sediments ranging in age from Permo-Carboniferous to recent and which represent continental, lacustrine and marine conditions of deposition. Igneous and pyroclastic rocks are confined to Jombo Hill, and alkaline intrusion, and associated satellite vent agglomerates and dykes. An account is given of the various rocks, their genesis and their structures, and an attempt is made to correlate them with other areas. The economic prospects of the area are assessed and the possibility of the presence of coal-bearing strata is discussed.
    • The Cowries of the East African Coast (Kenya, Tanganyika, Zanzibar and Pemba).

      Verdcourt, B. (1954)
      All the species known to occur on our coasts are included in this present paper. Rarities have been included since they are needed for the museum collections.
    • Preliminary Survey of the Pelagic Fishes of East Africa.

      Williams, F. (Her Majesty's Stationary OfficeLondon, UK, 1956)
      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.
    • Chemical Factors Limiting Growth of Phytoplankton in Lake Victoria.

      Fish, G.R. (1956)
      Investigations on the problem of phytoplankton productivity in the waters of Lake Victoria have been pursued since 1949. Observations from the shallow bays and inlets showed that no annual cycle of phytoplankton occurred. In view of the favourable climatic conditions found in this area, factors limiting growth of phytoplankton were sought in the form of deficiencies in chemical nutrients dissolved in the water.
    • A preliminary survey of the hydrography of the British East African coastal waters.

      Newell, B.S. (Her Majesty's Stationery OfficeLondon, UK, 1957)
      This report is an attempt to collate all available data both from previous sources and from this preliminary survey, in order to present as complete as possible a description of the East African coastal waters. It is clear from the results so far obtained that only prolonged and continuous investigation will suffice to delineate the hydrography of these waters, and such an investigation forms part of the programme of this organization.
    • Report to the Government of Kenya on the Sea Fisheries of Kenya June-July 1958. Based on the work of J.A. Crutchfield (FAO Technical Assistance Fishery Expert).

      Food and Agriculture OrganizationRome, Italy, 1958
      There is a widespread feeling among government and business officials that expansion of the Kenya coast fisheries is impeded by an inadequate and restrictive marketing structure. Various plans for improvement of the industry have been put forward by the trade -and by the Game Department's Fisheries Division, but all have been subject to vigorous objections from one or more groups concerned. The Kenya government therefore requested the Food and Agriculture Organization to assign a qualified person to survey the industry and to recommend measures for improve the marketing of sea fish. This request was subsequently broadened to include an appraisal of the need for a loan fund for Arab, African and Bajune soa fishermen.
    • Hydrography of the British East African Coastal waters, Part II.

      Newell, B.S. (Her Majesty's Stationery OfficeLondon, UK, 1959)
      The purpose of this second survey was twofold. Firstly, to confirm and amplify the deductions drawn from the previous survey, and secondly to obtain an estimate of the fertility of these waters. To this end, measurements were made of temperature, salinity, oxygen content, pH, total phosphate and inorganic phosphate throughout the water column from surface to about 500 metres. In October, 1956, an estimation of albuminoid nitrogen was also effected.
    • The Cowries of the East African coasts: Supplement II.

      Verdcourt, B. (1959)
      All the species known to occur on our coasts are included in this present paper.
    • An Investigation of the Biology and Culture of an East African Oyster Crassostrce cucullata.

      Van Someren, V.D.; Whitehead, P.J. (Her Majesty's Stationary OfficeLondon, England, 1961)
      CrassostrtZa cucullata (Born) is the most important edible oyster of the East African coast, and is .a purely littoral species occurring intertidally on open reefs, mangrove roots and creek rock exposures. Heavy commercial exploitation ofoyster beds on the Kenya coast has led to almost complete destruction of these beds, and in all areas the rate of natural regeneration and recovery of beds appears practically negligible, or at the best, an extremely slow process. Exploitation of beds, hitherto unlicensed, is now strictly controlled by Government. A survey of the biology and ecology ofoysters was carried out between September 1953 and August 1954, with further brief visits in October 1954 and September 1956, with particular reference to conditions in Mida Creek, one ofthe largest natural beds of oysters on mangroves. Here two forms of oyster occur; one, a spiked form growing on mangrove roots at higher tidal levels, and the other a flat form, growing at the lower levels. These appear to be distinct species, the latter being recognizable as C. cucullata; no attempt 4as been made to determine the identity ofthe former, which is referred to as Species A. The tidal and certain physico-chemical conditions in Mida are described in detail, these being different from those of the open shore, owing to the geographical formation of the Creek. The particular differences in each oyster zone are well marked. The oysters themselves are confined only to the eastern fringes of the mangrove forests, a spatial distribution which limits their abundance, and which may be due to the habit ofthe settling spat. They occur also on old reef rock expanses, and are phoretic on the abundant mollusc Terebralia palustris Brug. Zonation on the mangrove roots is distinct, and bears a strict relation to tidal levels. Temperatures, salinity and rainfall figures were noted, and their seasonal and local variations are described. Weekly dissections of adult oysters were made to determine spawning rhythms. While spent oysters may be found in armost any week ofthe year, and a low level ofspawning is continuous, nevertheless spawning sho~s two maximal periods coinciding with the onset of the rainy seasons in the year. The environmental factors related to spawning are complex, and it is suggested that (a) maximal water temperatures oYer 85"F (29'S°C), (b) the immediate onset of rain and (c) a fall in salinity are jointly responsihle for major spawning activity. While natural spat is very rare on all Kenya oyster beds, nevertheless a variety of spat collecting devices tried at Mida showed that spat would settle readily on Mangalore tile collectors, and shell culch strung on wires. The importance of cleanliness of spat collectors is not yet fully established for Kenya conditions and further trials are required both in this connection and that of the most suitable method in which to arrange the collector and the best type of collector. Itis, however, certain that some form of cultural method, using spat collectors, is fully practicable. While spat may settle at almost any time of the year, the heaviest spatfalls occurred at the beginning of, and during, the rainy seasons of November/December and April/May, the latter season providing maximal spatfall. The duration of free swimming larval life is not, however, known. All spat collected settled within a few inches ofground level, and appeared to be that of C. cuculla!a. Under natural conditions spatfall is fractional only, and the evidence suggests that the spat settle by preference on hard surfaces, mangrove bark being a second "choice". The conditions influencing settlement of spat are discussed. Growth of spat collected at Mida is very fast, averaging about 0·6 em a month; at only seven months the young oysters have reached the average adult length, but not thickness; thickness is added during the second year of life, and artificially grown oysters reach marketable size in about 2! to 3 years. Spat from elsewhere, grown at Mida, does not grow so fast, nor does Mida spat at levels above their normal tidal zone. Growth or survival of spat under pennanent submerged conditions is not known• Natural mortality of spat is not particularly heavy, nor apparently are there many serious natural predators. The growth of spat may vary according to season, but once adult, the oysters apparently cease to grow. Size at first maturity is not known. The preliminary results indicate that artificial culture of these Kenya C. cucul/ata oysters on shell culch strung on wires, and on tile collectors, would be practicable and economic, and indeed essential if exploitation is to continue at its present level. Possible cultural methods are discussed, and in places such as Mida or Ngomeni reef, there are large potentially productive areas which could be utilised for such culture.
    • Breeding Studies on Tilapia Zillii and Tilapia Nigra.

      Cridland, C. (East African Freshwater Fishery Research OrganizationJinjga, Uganda, 1961)
      Broods were recorded from seven pairs of T. zilli which had been reared from previous experiments in the laboratory, observations on these being made for a period of 19 months.
    • Preliminary notes on the relationship between Feeding and Growth Rate in the Siluroid Fish Bagrus docmac (Forsk).

      Elder, H.Y. (East African Freshwater Fishery Research Organization,Jinja, Uganda, 1961)
      Experiments were begun in April to clarify the relationship between Bagrus and its main prey in the natural environment of L. Victoria, the cichlid fish of the genus Haplochromis. Some of the results of the first two parts of these experiments, the relationship between size and basic food requirement and between feeding rate and growth rate are discussed in more detail in this appendix.
    • River Fish Migration.

      Van Someren, V. (East African Freshwater Fishery Research OrganizationJinja, Uganda, 1961)
      For the last four years an inclined grid trap has been maintained on the Ragati River which flows through the Sagana Fishery Research Station in Kenya. For a number of reasons, mainly financial, it was not possible to make this trap operable at full efficiency throughout the flood period of every year since it was constructed in 1958, nor has the part for trapping upstream migrants been entirely successful. However, it has now been possible to collate all data collected so far on the migration of fish at this trap, and the full results are being published elsewhere.
    • Report on Limnological Work during a Visit to EAFFRO between, August 1980, and September 1961

      Talling, J. (East African Freshwater Fishery Research OrganizationJinja, Uganda, 1961)
      Work has been carried out on several aspects of algal productivity in Lake Victoria waters, in relation to a background of physical and chemical Limnology. Routine sampling of the offshore waters of Lake Victoria was maintained as the most detailed approach, but the collection of comparative data from other waters was made.
    • Pond Culture Studies on Tilapia Nigra.

      Van Someren, V. (East African Freshwater Fishery Research OrganizationJinja, Uganda, 1961)
      The culture of T. nigra in ponds is best effected monosex methods, in order to obtain yields of fish a1l of a uniformly large size after a period of time. It is usual to grow males only, stocking them on a basis of sex separation carried out either by genital examination of immature fish, or on colour of the pelvic fin in mature fish taken from a mixed stock pond, The technique and subsequent growth features have been fully described.