• 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.
    • Present and Future Perspectives on Marine Affairs in Kenya.

      Makau, B.F.; Okidi, C.O.; Westley, S. (University of Nairobi, Institute for Development StudiesNairobi, Kenya, 1978)
      The Science and Technology Act (No,3 of 1977) was recently passed by Parliament, thereby establishing machinery in the form of the National Council for Science and Technology (NCST) to advise the Kenya government on a national science policy and coordinate related matters. One of the basic tasks which the NCST will carry out towards the goal of formulating a national science policy will be the identification and costing of projects. This will give the NSCT an insight into the state of any branch of science and technology in the country. In the case of marine sciences the NCST, operating on an ad hoc basis, appointed a Working Party of experts in November 1975 to examine the need for a Marine Resources Institute in Kenya. Involvement in this exercise has given the NCST a general view of the state of marine activities in the country. This short paper is not a presentation of the report of the Working Party, but it contains the highlights of what was found during the investigations.
    • Coastal Aquaculture Potential of East Africa

      Bwathondi, P.O.; Institute of Marine Sciences (1981)
      Studies on the aquaculture potential of East African coast has been given. Due to the large expanse of mangrove areas in the region, it has been suggested that the culture of penaeid prawns, particularly Penaeus indicus (H. Milne Edwards), P. monodon (Fabricius), P.semisulcatus (De Haan) and Metapenaeus monoceros (Fabricius) be attempted in the mangrove areas and creeks. Such rearing experiments should be run concurrently with experiments involving the breeding of the prawns in the laboratory. Experiments carried out on the rearing of mollusks show that the region does not support any appreciable growth of oysters, particularly the commercial species. The dominant genera in the region are Ostrea and Crassostrea. The former genus has a slow growth rate and little meat yield. Experiments are underway to determine the aquaculture potential of mussels. Fish culture, particularly the culture of rabbitfish Siganus spp. has a promising future in the region. Rearing experiments carried out at the Institute of Marine Sciences, University of Dar es Salaam, Zanzibar, have indicated that the fish can be cultured to maturity size of 23.4 cm total length within about 8-9 months. The growth rate of this fish has also been determined by the author. Other fish which have a promising aquaculture potential in the region are milkfish Chanos spp; and Epinephelus spp. The study of seaweeds of Tanzania has reached an advanced stage. Already researches are underway to open seaweed farms both in Zanzibar and Pemba Islands and along the coast of Tanzania Mainland. One of the most valuable seaweeds which has attracted great attention in the region is Eucheuma spp.
    • The Co-existence between Oreochromis niloticus and Lates niloticus in Lake Victoria (Kenya Sector).

      Ogari, J.; Bwathondi, P.O.J. (Kenya Marine and Fisheries Research InstituteMombasa, Kenya, 1990)
      The present study was undertaken to try and find out why Lates niloticus and Oreochromis niloticus have managed to co-exist in Lake Victoria (Kenya sector). The study is considered to be of tremendous scientific value not only because lates has been accused of preying on the cichlid stocks in L.Victoria but also for considering suitable management approaches to maintain viable fishery resources on long-term basis. The results presented are preliminary and the final detailed results will be presented later when the survey will have been accomplished.
    • Large Marine Ecosystems Concept Applied to Managing Offshore Zones and Marine Resources: Kenya's Contribution.

      Okemwa, Ezekiel; Ntiba, M.; Miles, Edward L.; Treves, Tullio (The Law of the Sea Institute, William S. Richardson. School of Law, University of HawaiiHonolulu, Hawaii, 1992)
      The Kenya coast represents one of the most unique biotic regions of the world, containing a wide variety of ecosystems: mangrove forest, seagrass, coral reef, and open sea. A rich diversity of plants and animals, many endemic, are found within these ecosystems. Kenya's coastal biodiversity resources, both economic and environmental, are of critical value to Kenya and to the global community. Continued loss of biodiversity forecloses opportunities for future generations to benefit from the many known and potential values in increases of biodiversity. The maintenance of biodiversity is essential to meet present and future development needs. The ecological integrity of natural communities, particularly Kenyan ones rich in diverse marine wildlife, represents an important prospective and actual economic value through tourism and marine wildlife utilization.
    • The composition and structure of the plankton community in the Tudor creek, Mombasa, Kenya.

      Okemwa, E. (Swedish Agency for Research Cooperation with Developing Countries (SAREC)Stockholm, Sweden, 1993)
      This study was undertaken with a view to describing the species composition and the community structure of copepods in the Tudor Creek, Mombasa, Kenya. The first quantative study of the pelagic zooplankton community of the Tudor Creek was undertaken from December 1984 to December 1987. Between December and March 1985 a Bongo plankton net of. 335 ~km mesh size was used from the vessel ”R.V. Maumba”. From April 1985 to December 1987 a conical plankton net was used from a small canoe equipped with an outboord engine. The net, with a mesh aperture size of 335 ~km, a length of 1 m, and 45 cm in diameter at the mouth, was fitted with aflow meterat the mouth. Surface plankton samples were taken from September 1985 to August 1986 using a small canoe at each of five permanent stations during day-and night-time, at one neap and one spring tide each month. Thereafter only day-time neap and spring tide samples were taken from September 1986 to December 1987 at the five stations. 24hours cycle sampling was occasionally done at stations 1and 5 simultaneously. Results from the study shows that zooplankton are rich and abundant. Over 51 taXil were recorded. Close to74 % of the zooplankton comprised copepods of which the most important were calanoids followed by cyclopoids, poecilostomatoids, harpacticoids and monstrilloids. The most commonly encountered calanoid species were Centropages orsinii, Acrocalanus longicornis, Clausocalanus tarrani, Temora turbinata, Paracalanus aculeatis, P. simplex, Canthocalanus pauper, Undinula vulgaris, Acartia danae, Euchaeta marina and Eucalanus spp. The most common cyclopoid and harpacticoid species encountered were Corycaeus specious, Oncaea venusta, Copilia mirabilis, Sapphirina laetens. Oithona plumifera, O. setigera, O. simplex and Microsetella rosea, Euterpina acutifrons. Macrosetella sracilis respectively. Only occasionally did copepods of the order Monstrilloida appear in the samples. Some 99 copepod species, representing 41 genera and 30 families, have been identified. Amongst these,17 species were dominant but 6 of these including; Calanus darwini. Labidocera laevidentata, Paracalanus crassirostris, P.indicus. P.tropicus and Sapphirina lactens, were recorded for the first time in the Western Indian Ocean off the Kenyan coast.
    • Initial results of the benthic fauna studies in the northern Lake Victoria

      Mbahinzireki, G.B. (ICIPE Science Press, 1994)
      The paper presents initial results of relative abundance, composition and distribution of benthic organisms in an ecologically and environmentally changing northern Lake Victoria. The results suggest that the density of most of the zoobenthos has gone up since the pre-perch era despite the absence of comparative data. Increases in densities were noted for dipteran larvae followed by Caridina nilotica, ostracods, oligochaetes, molluscs and nymphs of Anisoptera and Ephemeroptera, in that order. Possible reasons to account for the increase are advanced. Inshore stations held higher densities than the offshore station. Type of the sediment and physico-chemical factors seem to influence the production and distribution of these communities.
    • Survival rates of Lates niloticus in Lake Victoria

      Asila, A.A. (ICIPE SCIENCE, 1994)
      Survival rates of Lates niloticus in Lake Victoria, Kenya were adduced from length derived age specific lifetables. Nature of the populations were inferred from calculated parameters. Unstable populations were observed between 1989 and 1992, which would subsequently lead to decreased catches between 1990 and 1994.
    • Multigear fishery of Nile perch (Lates niloticus) in the Winam Gulf of Lake Victoria: with special reference to mortality, selection and catch/effort data

      Manyala, J.O.; Rabuor, C.O. (ICIPE SCIENCE, 1994)
      A survey of multigear fishery of Nile perch (Lates niloticus) in the Winam Gulf of Lake Victoria indicates that total mortality coefficient (Z) determined from longline fishery using hook number 6 was double that of hook number 7. Total mortality coefficient determined from gillnets and beachseines were lower than those of hooks. The catch per unit effort (C/f) measured using different criteria indicated an increase for all gears in 1990 as compared to 1989 except for gillnets. A two-fold increase in unit effort (f) increased the C/f for mosquito seines by only 30%. The typical exponential decay of C/f with increasing f of exploited stock in equilibrium was lacking in the case of Nile perch in the Winam Gulf.
    • Some biological and ecological considerations for research in the management of the fisheries of Lakes Victoria and Kyoga

      Twongo, T. (Nairobi : ICIPE SCIENCE, 1994)
      The total landings of fish from Lake Victoria (Ugandan sector) have increased after the explosive increase in stocks and the apparent abrupt increase of fishing effort. This paper analyses fish production during the last decade, capture methods, processing, and marketing and management policies.
    • Some observations on the African catfish Clarias gariepinus (Burchell) in the Sondu-Miriu River of Lake Victoria, Kenya

      Lung'ayia, H.B.O. (ICIPE SCIENCE, 1994)
      The African catfish Clarias gariepinus (Burchell), has an intermitent occurrence in the Sondu-Miriu river draining into lake Victoria. Observations were made to get basic information on size composition, migration, spawning period and food of this species in the river. A total of 376 fish samples of fish ranging from 11.9 to 101.1 cm in total length were examined from January to December 1989. A migration of the fish between the lake and the river waters is indicated. Small sized and immature fish were available in the river throughout the year but their numbers became minimal in the dry season. Large and mature specimens were caught mainly during the high water mark and rainy seasons of April-June and September-October, suggesting an upstream spawning migration. First maturity for both sexes was observed at 21.0 cm total length. The overall female to male ratio was 1:2. The food was mainly composed of fish, detritus, plants, crustaceans and insects. The study is a contribution to the understanding of the biology of C. gariepinus in the lake-river ecosystem.
    • The management and directions for future research on Lake Victoria multispecies fisheries

      Okemwa, E. (ICIPE SCIENCE, 1994)
      A brief review is presented on some of the measures taken to manage Lake Victoria multispecies fisheries. It is suggested that management enforcement is not working. The linkage between research, policy making, industry and artisanal fishery is considered. The paper examines how the whole process of taking management decisions might be modified to take into account the realities of life in the riparian states around the lake and of the complexities and uncertainties of multispecies fisheries. Research and assessment are considered. Understanding the multispecies fisheries and characteristics of contemporary fisheries management are described. Recommendations for future research are given.
    • Suggestions to set mesh size limits and restrict the fishing methods and the types of fishing gears on Lakes Victoria and Kyoga

      Ogutu-Ohwayo, R.; Twongo, T.; Wandera, S.B.; Balirwa, J.B. (ICIPE SCIENCE, 1994)
      On the basis of observations, it is recommended that 127 mm should be the minimum mesh size of gillnet permitted on Lakes Victoria and Kyoga. The minimum length of Nile tilapia (Oreochromis niloticus) should remain at 28 cm but that of Nile perch (Lates niloticus) should be increased from 46 cm to 50 cm. The minimum mesh size limit of seine net for Mukene on Lake Victoria should be 10 mm and fishing for Mukene should be done using lampara net operated offshore.
    • Mortality rate, exploitation and recruitment in Oreochromis niloticus (Linnaeus) in Nyanza Gulf of Lake Victoria, Kenya

      Getabu, A. (ICIPE SCIENCE, 1994)
      An analysis was done on length frequency data to study mortality, exploitation rate and recruitment in Oreochromis niloticus in Nyanza Gulf, Lake Victoria. The fishing mortality (F) and natural mortality (M) were 0.468 y super(-1) and 2.0 y super(-1) respectively. The exploitation rate was 57.2%. Yield per recruit under the fishing regime was 250 g. Its predicted value at maximum sustained yield was 530 g, which could be obtained at a fishing mortality of 1.5 y super(-1). The recommended value was 500 g to be obtained at a fishing mortality of 1.0 y super(-1). The maximum biomass per recruit (B/R) was 1132.48 g while the optimum was 1068.38 g. The biomass recruit under the present fishing regime is 534.19 g which is too low. There is severe overfishing as there are a lot of immature fish in the catch. The analysis shows that the yield can double if the recommended mesh size is adopted in the fishery.
    • The occurrence of ichthyoparasites and their effects on the fisheries of the Lake Victoria Basin, Kenya

      Ogwai, C. (ICIPE SCIENCE, 1994)
      The occurrence of ichthyoparasites and their cumulative effects was observed at the inner Nyanza Gulf region of Lake Victoria. Protozoa, Nematoda, Cestoda, Crustacea and Trematoda are mentioned. The parasite fauna and the biocoenology of the hosts were studied and the seasonal variation in infectivity was observed. Infection in the dams was prevalent and was 75% at the peak. Some gill infected specimens were examined between July and February. Infestation rates were higher during the dry season. Males and juveniles dominated the infected samples throughout the study period. The distribution pattern of the hosts was also noted.
    • Preliminary study on the food and feeding habits of Schilbe mystus (Linn., 1762) in River Nyando

      Omondi, R.; Ogari, J. (ICIPE SCIENCE, 1994)
      Schilbe mystus (butterfish) is one of the "endangered species" of Lake Victoria, whose fishery was once of commercial importance. The annual landings have declined from about 400 mt in 1968 to a bare 15 mt in 1991. The average size of the species is smaller than that reported by Greenwood (1966). During the study, the size range sampled was 11.2 to 25.6 cm fork length with the majority measuring 14.0-15.0 cm FL. The food and feeding habits of the fish are discussed. Study on the gut content shows that S. mystus preys mainly on insects with chironomid larvae as the dominant prey.
    • The biology and distribution of Haplochromis spp in the Nyanza Gulf prior to the total invasion of the Gulf of Nile perch, Lates niloticus (L)

      Mwalo, O.M. (ICIPE SCIENCE, 1994)
      The work reported was conducted during the watershed period of 1976 when Nile perch (Lates niloticus) started to replace Haplochromis spp. in dominance in the Nyanza Gulf of Lake Victoria. Seventy four "groups" of Haplochromis species flock obtained from a stock assessment survey of that year were used in the study. The length of fish examined varied between 57 and 237 mm total length, and between 1 and 182 g wet weight, with means of 101.05 mm and 18.53 g respectively. Frequency distribution curves for both sexes were unimodal with a maximum between 70 and 130 mm. The t-test showed that the two sexes came from the same population. Clutch size per fish (mean weight 25.3 g and mean total length 106.7 mm) was 78 eggs. The minimum size at maturity was 89 mm for males and 93 mm for females. Living condition coefficient was highest at developing stages. Sex ratio calculations per "group" were found illogical as most "groups" were exclusively monosexual. Most of the Haplochromine "groups" fed on phytoplankton (41%), others on molluscs (21%), fish material (12%), insect larvae (9%), adult insects (8%), macrophytic detritus including sand grains (7%) and zooplankton (4%). Feeding competition was lowest among the grazers on the abundant phytoplankton and highest among the adult aquatic insect eaters. Nematode parasitic infestation was common among female fish. Haplochromis spp. were collected in all the hauls and usually in greatest concentrations from a depth of 4 m through to 49 m. Over 80% of the 74 "groups" were represented in the 4-9 m depth interval, 59% in the 10-19 m depth interval, 68% in the 20-29 m depth interval, 30% in the 30-49 m depth interval and only about 10% of the groups were represented in the deepest 50-69 m depth interval.
    • Observations on the fisheries, growth and mortality rate of Oreochromis niloticus (tilapia) in the Nyanza Gulf of Lake Victoria.

      Dache, S. (ICIPE SCIENCE, 1994)
      Oreochromis niloticus forms the third most important commercial fishery in Lake Victoria after Lates niloticus and Rastrineobola argentea. Because of its commercial importance as a cheap source of animal protein, a study of its landing trends, growth and mortality rates was conducted to assess the state of its stock in the lake and recommend guidelines for its exploitation and management. To arrive at the trends, landing data between 1976 and 1989 were analysed. For the estimation of the growth and mortality rates, length frequency data were collected from trawl surveys conducted fortnight between Sseptember, 1989 and August, 1990 in the Nyanza Gulf. The results show increased landings during the study period, with a higher percentage landed in the open waters of the lake. The length-frequency results show that O. niloticus is a slow growing fish which attains a great asymptotic length of 61.3 cm, a growth constant K of 0.35 yr super(-1) and a high growth performance index phi of 3.12. The total, natural and fishing mortality rates were estimated at 1.71 yr super(-1) and 0.72, 0.99 yr super(-1) respectively. It is concluded from these studies that O. niloticus has a high growth performance index attaining larger sizes and if well managed, its fishery may flourish and sustain the protein supply to the people living around the lake.
    • Floodplain fishery of the lower Sondu-Miriu River with emphasis on the Nile perch (Lates niloticus) (Linnaeus)

      Manyala, J.O. (ICIPE SCIENCE, 1994)
      Experimental beach seine surveys in 1990 in the lower Sondu-Miriu River in Kenya indicate a potential catch rate of up to 59.8 kg ha super(-1) hr super(-1). Lates niloticus dominated the catches in the lower reaches (37.5%), while catches in the upper reaches were dominated by Labeo victorianus, Schilbe mystus and Barbus altianalis. L. victorianus contributed up to 84.8% of the catch in the upper reaches by weight. Catches in the floodplain were dominated by Oreochromis niloticus, O. variabilis and Clarias gariepinus, which contributed more than 50% by weight. The size frequency distribution of L. niloticus suggests that larger specimens occur in the river as compared to the floodplain.
    • Some aspects of the reproductive biology of the Nile tilapia Oreochromis niloticus (L) in the Nyanza Gulf of Lake Victoria, Kenya

      Lung'ayia, H.B.O. (ICIPE SCIENCE, 1994)
      Some aspects of the reproductive biology of the Nile tilapia, Oreochromis niloticus population in the Nyanza Gulf of lake Victoria, Kenya were investigated from March to August 1991. The overall sex ratio was 2.08:1 in favour of males. A variation in sex ratio was observed with females predominating over males in lengths between 37.5 and 41.0 cm total length. Fecundity ranged from 864 to 6316 eggs with an average of 2141. The relationship between fecundity (F), and total length (L) and weight (W) was F=22.755 L super(1.2141); F=177.142 W super(0.342). The fecundity was compared to that reported elsewhere and together with spawning habits, were suggested as some of that factors contributing to the abundance of the Nile tilapia over other tilapiine fish species in Lake Victoria.