• Asteroidea of Mombasa Marine National Park and Reserve.

      Eekelers, Dirk (Vrije Universiteit Brussel, 1970)
      Biodiversity, abundance, feeding preference and habitat data on an assemblage of shallow water, coral-reef starfish (Asteroidea) were gathered over four months at Mombasa National Marine Park and Reserve. M1VINP&R contain a fringing reef and are situated between Mombasa town and Mtwapa creek on the East African coast of the Western Indian Ocean. It has not been known to carry an outbreak of the corallivorous crown-of-thorns starfish (Acanthaster planci) and its coral cover is well developed. Specimens required primarily for identification were collected by means of circlesampling, time transects and random searches. In addition, a selection of large and small, dead coral slabs were overturned and cryptic specimens located beneath these slabs were collected. Data for the abundance investigation was collected by means of 30' time transects in the inner and outer-reef. In the shallow inner-reef the surveys were done using snorkelling equipment while investigation of the outer-reef was done with the use of SCUBA gear. Additional investigation was done to obtain information about the habitat preferences of the species. When doing the transects for habitat, abundance or species presence surveys, species were turned over to detect the food preference of the animals. The identifications of the species were done under supervision of Prof. Jangoux at the laboratory for Oceanology, ULB Brussels. The finding of Choriaster granulatus, Fromia monilis, Neoferdina kuhli are new records for East Africa while Halityle regularis, Pentaceraster horridus, Pentaceraster tuberculatus and Euretaster cribrosus represent new records for the coast of Kenya It was found that MMNP&R carries a rich and diverse asterooid fauna but the imperfectness of the time transect method especially in regard to cryptic species indicates that additional species are still to be located. Of the 18 starfish species found in M1VINP&R, 6 (Choreaster granulatus, Fromia monilis, Gomophia egyptica, Linclda multiflore, Nardoa variolata and Neoferdina kuhli) were located only in the outer-reef. An additional seven species (Halityle regularis, Pentaceraster horridus, P. mammillatus, P. tuberculatus, Leiaster coriaceus, Asterina burtoni and Euretaster cribrosus) were found only in the inner-reef. Some specimens were located in the inner as well as the outer-reef (Acanthaster planci, Culcila schmideliana, Protoreaster lincki, Linckia laevigata and L. guidingii), though a preference for one of the reefs was obvious for some of these species. None of the species were found in intertidal areas. While, Acanthastar planci, Fromia monilis, Gomophia egyptiaca, Linckia multiphora, Neoferdina kuhli and Nardoa variolata were sometimes found at the base of the reef slope, they were never observed on the sea floor away from the reef The preceding species can be regarded as coral-reef species and their distribution differs from that of species such as Choreaster granulatus and Culcita schmideliana that were also found in the deeper off-reef waters in the MNP&R region or Pentaceraster spp and Protoreaster lincki who were manly found in the inner-reefs sea grass beds. The observation that most species (all except one) of , starfish found on MMNP&R belong to the order of the Valvatida corresponds with the results of other investigations done in the tropical regions, and a general increase in relative significance of this order toward the tropics is noted. The asteroids found on MMNP&R showed some inter-specific variation with respect to die but most species appeared to feed on in the inner-reef there is a general increase of the total number of starfish from the park to the reserve. This is most likely an effect of the full protection status of the park in regard to fishery, which is reflected in a higher density of the main predator of the starfish (the triggerfish Balistapus undulatus) at the park. In the park's outer-reef a dominance of Linckias was noted;, these species are well known for their extraordinary regenerative capacities and their autonomous asexual reproduction capabilities. These qualities surely increase their surviving opportunities in an area with high predation pressure. The asteroid communities of MMNP&R were clearly adult-dominated, although the juveniles of these species might complete their early development under boulders and are for that reason difficult to detect with the used method. Still, many workers who have studied coral reef asteroid populations have noted the adult-dominated size structure of these populations.
    • Design of an Efficient Fishing Vessel for the East African Coast.

      Shiundu, Juvenal J.M. (University of Newcastle upon Tyne, 1983)
      This project is divided into two parts, Part A is a feasibility study in which a brief background study of the Kenya Fisheries Department, fishing vessels, efforts and the areas being fished is examined. Fish species, catch and market potential are also examined. From the inference in Part A, a design of a fishing vessel suitable to the local conditions has been developed in Part B. The building cost of the new design was estimated and an economic evaluation studied using the net present value as a measure of merit.
    • Marine Phytal Harpacticoida from Kenya with emphasis on seagrass dwelling species.

      Demeulenaere, Bruno (Free University of Brussels, 1991)
      In the present work. diversity and abundance of seagrass dwelling harpacticoid copepods are determined. By means of difference in diversity between the Gazi Bay and English point harpacticoid assemblages and the use of TWINSPAN analysis. the use of harpacticoids as a sensitive tool in pollution monitoring is evaluated. This is completed by a brief discussion of the usefulness of the different diversity indices. A second part comprises (re) descriptions of some species together with some remarks on interesting features of other species and an updating of geographical distribution.
    • Ecological study of the benthos of the mangroves and surrounding beaches at Gazi Bay, Kenya - Summary.

      Schrijvers, Jan (University of Ghent, 1991)
      This thesis is part of the EC-project ”Dynamics and Assessment of the mangrove ecosystem in Kenya” (1989-1992). Its general aim is to analyse the mangrove ecosystem in all its elements in order to propose conservation strategies. To understand the intrinsic ecology of mangrove areas (fig. 1) and the interaction between mangrove areas and other ecosystems, such as oceans and coral-reefs, it is necessary to study as many compartments of the ecosystem as possible. My contribution to this project is the study of the benthos (e.g. infauna); so far few data exist about the ecology of benthic communities in the tropics (RUWA, 1990). The community-ecological picture of the meio-and macrozoobenthos of the mangroves of Gazi Bay, near Mombasa, Kenya, is presented. Habitats differing according to the type of mangrove vegetation (namely Avicennia, Bruguiera, Ceriops, Rhizophora and Sonneratia) and to the sediment in all its characteristics (e.g. sandflat-mangrove, inundation,...) are investigated. The abiotic data have been written down as completely as possible. Densities, diversities and biomass data of the benthos (e.g. infauna)have been calculated and, where possible, mathematically processed in order to produce a reliable community ecological pattern.
    • Dynamics of carbon and nitrogen in the mangrove forest of Gazi, Kenya: a numerical modelling approach

      Ong'anda, H.O. (Free University of Brussels, 1992)
      The numerical model described in this work has been designed to study the flow of carbon and nitrogen in a mangrove forest at Gazi Bay, Kenya. Several processes and storages of matter considered vital in the functioning of the ecosystem have been reviewed to help in the abstraction of the model and analysis. A numerical model represents the functioning of the ecosystem but is always limited due to the complexity of the system and lack of information on processes. A review of modelling work concerned with coastal ecosystems reveals that modelling is not only a means of summarising data from field studies, but that it can also be an integrated part of research effort useful in formulating research hypotheses and drawing up management options. The objectives of the Gazi model are similar in this respect. The abstraction of the system is presented as a box and arrow diagram showing storages and flows of matter. Changes in each of the state variables are function of some input and output processes and are represented in the model equations as ordinary differential equations. The processes are variously formulated using published ecosystem models, field data and personal effort. For ease of conceptualisation the modelling exercise has been handled in several submodels. The majority of the rate coefficients were estimated from field and literature values whereas a few others were chosen arbitrarily. Computer simulation of the system was done in an IBM compatible PC using a simulation package. A sensitivity analysis was carried out to investigate the sensitivity of the model to changes in input and parameter values. The favourable comparison between model output and information available points to the relative accuracy of the model. The results show that the nutrient contribution of the mangrove ecosystem to the contiguous zones is negative. The system exports carbon largely consisting of detritus poor in nitrogen. The flow of nitrogen through bacteria accounts for 72% of the total system nitrogen through flow (not including the import of nitrogen into the system). The mangrove ecosystem strongly consumes nitrogen and compensates for this by using inorganic nitrogen in the tidal water and possibly from sheetflow and underground seepage. More information is needed on the grazing habits of detritivores.
    • Qualitative and Quantitative Structural Characteristics of Tile Teleostean Kidney.

      Kamunde, Collins Nkonge (University of Nairobi, 1993)
      The kidneys of four freshwater teleost fish Oreochromis niloticus, Micropterus salmoides, Cyprinus carpio and Clarias mossambicus and one marine teleost, Chanos chanos, representing Perciformes (O. niloticus & M. salmoides) Ostariophysi (C. carpio, & C. mossambicus ) and Salmoniformes (C. chanos were studied for qualitative and quantitative characteristics using materials fixed in situ by perfusion via the bulbous arteriosus into the entire renal arterial system. The kidneys of O. niloticus, M. salmoides and C. carpio were partially fused and those of C. mossambicus and C. chanos were completely fused. Partial or complete venous portal systems were present in all the species except O. niloticus. The renal lobule was centered around the intralobular artery and duct and delimited by efferent veins. The nephron of the fishes consisted of a renal corpuscle, the neck, proximal I, proximal II and distal segments and the collecting tubule-collecting duct system. These parts of the nephric tubule were distinguished on the basis of their stai ning reactio ns and histo log ical and ultrastructural characteristics. Intrarenal heamopoietic tissue was absent in the Perciformes teleosts but was abundant in the Ostariophysi and Salmoniformes. Interrenal tissue in the head kidney was arranged in cords arou nd branches of the posterior cardinal vein.Rodlet cells have been described in the proximal tubule of the blackbass. Kidney voiume per gram body weight ranged from 2.2-6.13 m m 3/g and was well correlated with body weight, the correlation coefficient (r) was 0.96. The allometric equation relating kidney volume (Vk) to body weight (W) was Vk == 3.236WO.977. The mean (±S.D.) values for the volume proportions of uriniferous tissue, total vascular space (all blood vessels and capillaries), ureter and its ducts and connective tissue were 52.56±14.93%, 29.59±2.20%,4.04±2.44% and 2.43±0.83°/0 respectively; however, renal haemopoietic tissue formed 31.62±4.38% in the kidneys of 3 species namely C. carpio, C. mossambicus and C. chanos). The absolute volumes of the main components of the teleostean kidney namely the uriniferous tissue (Vut) and the total vascular space (Vtvs) were strongly correlated with body weight and the allometric equations and correlation coefficients relating these parameters were: Vut = 1.102W1.077, r = 0.97 and Vtvs = 1.197W1.025, r = 0.96 respectively. The fish were divided into three categories each with two groups with contrasting characteristics; (1) percoid and ostariophysian, (2) fish with and without intrarenal haemopoietic tissue and (3) freshwater and marine fish. In each category Student's t-test was used to assess the differences between kidney weight per gram body weight and those between the respective volume proportions of renal corpuscles, uriniferous tissue, total vascular space and renal tubules. The differences between the values of all parameters, except the kidney volume per gram body weight and the volume proportions of renal tubules in freshwater and marine fish, in the two groups of each category were significant (P < 0.05). These results show that the quantitative characteristics of the teleost kidney are influenced by the order, habitat and distribution of intrarenal haemopoietic tissue.
    • Water Exchange and Channel Friction Related to Tidal Flow in Tudor Creek System, Kenya Coast, Western Indian Ocean.

      Nguli, Michael Mutua (University of Goteborg, 1994)
      The Tudor creek system, located in mid-Kenya coast is formed by a sinuous channel, Tudor channel, between Mombasa port and Tudor harbour, which connects the inner wide and shallow basin, the Tudor creek, to Kilindini harbour and the Western Indian Ocean. Two seasonal rivers, Kombeni and Tsivu enter it. The creek is surrounded by mangrove wetlands, while it's off-shore area is shielded by shore-parallel reefs on both sides of the entrance. We have studied the tidal flow in the channel by RCMs and the tidal heights within the creek and outside with tide gauges obtaining the following results. The tide is semidiurnal with a form number of 0.18. The neap and spring tidal range is 1.7 m and 3.1 m in the creek. The flood tide lasts 6.5h while ebb tide extends for 6.3h. Mean flood and ebb currents are 0.36 ms-1 and 0.40 ms-1 respectively. There is a marginal phase lag between the entrance and the creek. A high evaporation compared to fresh-water input during peak dry period, influence the salinities. During this season the creek is well mixed with lower salinity water on the oceanic side and high salinity water in the creek. The average volume flux due to the tide is 2600m3s-1 but the net exchange of water related to the residence time is 60 m3s-1 The residence time as determined from the NE monsoon peak dry season is of the order of two weeks. The bottom layer parameters; friction velocity, roughness length and drag coefficient have been estimated from pendelum current measurements assuming a logarithmic profile. Average values were 0.04 m s-1, 0.34 m, and 8.3 x 10-3 respectively. Heat flux and radiation balance is studied on the basis of temperature measurements.
    • The Larval Development and Juvenile Growth of the Silver Mouth Turban, Turbo argyrostomus.

      Kimani, Edward Ndirui (University of the Ryukyus, Japan, 1996)
      The silver mouth turban, Turbo argyrostomus L. 1758, is an archeogastropod widely distributed throughout the Indo-Pacific region. It is an important marine resource, harvested for food, marine souvenirs and ornamental items. Mass seed production techniques for Turbo marmoratus and T. argyrostomus, based on the techniques developed for Trochus niloticus in Palau, are currently being developed in the Okinawa prefecture, Japan, to replenish the declining populations of these commercial turbinids. Here, I report on the larval development, metamorphosis and the effect of diet on growth and shell characters of silver mouth turban juveniles, raised in the laboratory. I studied the larval development, metamorphosis and juvenile growth of T. argyrostomus between August 1995 and July 1996. Adults collected from Komesu, southern Okinawa Island, were induced to spawn by packing and UV sterilised seawater treatment on 9 August 1995. The green eggs (180-190 ~km in diameter) hatched within 18 hours, underwent torsion a few hours later and metamorphosed in 3-4 days after fertilization in the presence of metamorphosis inducing cues. Forty-eight percent of 200 competent veligers spontaneously metamorphosed in the absence of metamorphosis inducing cues between 7 days and 21 days after fertilization without feeding. The protoconch, 170-185 ~krn diameter, was colorless and globose in shape with irregular articulations. The juveniles grew to a mean shell length of 3.7 mm in 5 months (mean growth rate of 0.7 mm per month) feeding on microalgae growing on coral rubble and the sides of the aquaria, and grew to 11.5 mm in 9 months (mean growth rate of 2.7 mm per month) feeding on macroalgae. Small juveniles of mean shell length 3.9 mm, reared on a small fleshy red algae, Gelidiella acerosa, grew approximately 2 times faster than those reared on the green algae, Ulva purtusa, over 18 weeks. The combined diet of these two algae species gave higher growth rates than either algae individually, but did not improve growth significantly in large juveniles with an initial shell length of 5.8 mm. Percentage survival after 18 weeks was higher for juveniles reared on red algae (92.2 %,) compared to green algae (81.1%). The shell color of the snails depended on the algal diet. The shells of juveniles collected from the reef were heavier, for the same size, than those reared in the laboratory. The juveniles reared on mixed algae growing on coral rubble, collected from the reef, and the green algae had higher mean shell weights than snails reared on red algae alone or on a combination of green and red algae.
    • The Larval Development and Juvenile Growth of the Silver Mouth Turban, Turbo argyrostomus.

      Kimani, E.N. (University of the Ryukyus, 1996)
      The silver mouth turban, Turbo argyrostomus L. 1758, is an archeogastropod widely distributed throughout the Indo-Pacific region. It is an important marine resource, harvested for food, marine souvenirs and ornamental items. Mass seed production techniques for Turbo marmoratus and T. Argyrostomus, based on the techniques developed for Trochus niloticus in Palau, are currently being developed in the Okinawa prefecture, Japan, to replenish the declining populations of these commercial turbinids. Here, I report on the larval development, metamorphosis and the effect of diet on growth and shell characters of silver mouth turban juveniles, raised in the laboratory. I studied the larval development, metamorphosis and juvenile growth of T. argyrostomus between August 1995 and July 1996. Adults collected from Komesu, southern Okinawa Island, were induced to spawn by packing and UV sterilised seawater treatment on 9 August 1995. The green eggs (180-190 mu m in diameter) hatched within 18 hours, underwent torsion a few hours later and metamorphosis inducing cues. Forty-eight percent of 200 competent veligers spontaneously metamorphosed in the absence of metamorphosis inducing cues between 7 days and 21 days after fertilization without feeding. The protoconch, 170-185 mu m diameter, was colorless and globose in shape with irregular articulations. The juveniles grew to a mean shell length of 3.7mm in 5 months (mean growth rate of 0.7mm per month) feeding on microalgae growing on coral rubble and the sides of the aquaria, and grew to 11.5mm in 9 months (mean growth rate of 2.7mm per month) feeding on macroalgae. Small juveniles of mean shell length 3.9mm, reared on a small fleshy red algae, Gelidiella acerosa, grew approximately 2 times faster than those reared on the green algae, Ulva purtusa, over 18 weeks. The combined diet of these two algae species gave higher growth rates than either algae individually, but did not higher growth significantly in large juveniles with an initial shell length of 5.8mm. Percentage survival after 18 weeks was higher for juveniles reared on red algae (92.2%) compared to green algae (81.1%). The shell color of the snails depended on the algal diet. The shells of juveniles collected from the reef were heavier, for the same size, than those reared in the laboratory. The juveniles reared on mixed algae growing on coral rubble, collected from the reef, and the green algae had higher mean shell weights than snails reared on red algae alone or on a combination of green and red algae.
    • An Assessment of Nutrient Loading, Eutrophication and Plankton Dynamics in three Marine Tidal Creeks, Kenya: Port Reitz, Mtwapa Creek And Funzi Bay.

      Mvoyi, Chihenyo (University of Nairobi, 1999)
      Coastal marine eutrophication is recognised as a worldwide problem. On a global scale, it is now estimated that the input of nutrients especially various forms of nitrogen and phosphorus, to marine ecosystems from human sources via rivers are equal to or greater than, the natural input. The proposed study aims at assessing the eutrophication status of creeks to determine effects of nutrient loading on these ecosystems. This aim will be achieved by assessing the forms, concentrations and ratios of nitrogen and phosphorous as principal nutrients and how they affect rates of production and both phytoplankton and zooplankton compositions. The creeks have been chosen due to differences in nutrient loading. Port Reitz and Mtwapa creeks will be compared to Funzi bay, a relative pristine ecosystem. Sampling in these areas will be done taking into consideration, both point and non-point sources of anthropogenic nutrient loading. Physico-chemical parameters that will be analysed at each site include temperature, conductivity, dissolved oxygen and salinity. The various forms and concentrations of Nitrogen and Phosphorous will be analysed using various methods described for the analysis of nutrients in tropical seawater. Various phytoplankton and zooplankton compositions will be counted and analysed statistically using the Shannon-weaver method. The effects of nutrients on primary production, phytoplankton and zooplankton abundance will be determined in a bid to assess eutrophication and nutrient loading effects to productivity of these ecosystems. The information obtained during this study shall contribute significantly to the formulation of pollution/eutrophication control procedures as well as a basis for future research.
    • Environmental Factors and Coral Bleaching in Kenya.

      Mdodo, Rennatus Magina (Moi University, 1999)
      Elevated seawater temperature in March and April 1998 caused by the El Nino Southern Oscillation (ENSO) caused mass coral bleaching along the Kenya coast. The ENSO event had an effect on the climate of the study area and the region in general, with heavy rains starting in October 1997, and continuing to July 1998. Seawater temperature in March and April rose to an average 1.5 °C above values measured in the same period in 1997, with daytime low-tide highs of over 32°C. Coral bleaching is the whitening of corals resulting from the loss of symbiotic zooxanthellae and/or a reduction of the photosynthetic pigment concentrations in zooxanthellae. Bleaching was first observed in October 1997 in Kanamai during and after the El Nino rains, most likely due to sedimentation and seawater dilution in the shallow lagoon. In November 1997 bleaching was recorded in Malindi Marine National Park (MNP) and was mainly caused by sediment discharged from the Sabaki River. Later, extensive temperature induced bleaching and subsequent coral mortality was observed in mid March 1998 covering the entire coast of Kenya. Over 90% bleaching and mortality was recorded in Mombasa MNP, Malindi MNP and Kanamai. Bleaching and mortality was highest in the shallow lagoons such as Kanamai and areas where corals are exposed to sediment influence such as the north reef of Malindi MNP. The coral species most susceptible to bleaching and mortality were Porites nigrescens, Porites lutea, Acropora spp, Pocillopora spp and Stylophora pistillata. There was a distinct relationship between temperature and bleaching. As temperature increased to a maximum 32°C the number of normal coral colonies decreased due to bleaching and mortality. Temperature vs. bleaching relationship indicated a strong positive correlation for normal Porites nigrescens (r2 = 0.779), Porites lutea (r2 = 0.781) and Pocillopora sp (r2 = 0.803). The density of zooxanthellae ranged between 0.7 x 106 and 4.5 x 106 (mean, 2.5 x 106 ± 1.2 x 106, n = 11) per cm 2 for normal corals and 0.02 x 106 and 0.2 x 106 per cm 2 (Mean, 0.2 x 106 ± 0.02 x 106, n = 6) for bleached corals; Total loss of zooxanthellae and pigment was recorded in a few coral fragments. Zooxanthellae densities showed significant differences between species ((P<0.001) and between normal and bleached decussata had the highest zooxanthellae densities while Acropora sp and Stylophora pistillata had the lowest. The concentration of Chlorophyll-a ranged between 0.176 mg/cm2 and 0.795 mg/cm2 (Mean, 0.498 ± 0.287 mg/cm2 , n = 11) for normal corals and 0.002 mg/cm2 and 0.284 mg/cm2 (Mean, 0.0765 ± 0.01 mg/cm2, n = 6) for bleached corals. Chlorophyll-a concentrations differed significantly between bleached and normal colonies (p<0.005) and between species (p<O.OOI). In normal corals Porites nigrescens and Pavona decussata had the highest chlorophyll-a concentrations while Acropora sp and Stylophora pistillata had the lowest. Chlorophyll-a concentration per zooxanthellae was not significantly different between species but was significant between bleached and normal fragments (p<0.05). Bleached corals had higher values of chlorophyll-a per zooxanthellae compared to normal corals as can be observed in Acropora sp, porites nigrescens, porites lutea and Pavona decussata. Only in Slylophora pistillata that bleached fragments had a lower value of chlorophyll-a per zooxanthellae compared to the normal fragments. Overall this study indicates that coral bleaching and consequent mortality was caused by two sets of stressors; sediment/rainfall stress in Kanamai and Malindi in 1997 and elevated sea surface temperatures in all the sites in MarchiApri11998.
    • Kenya's Fishing Industry.

      Ikiara, M.M. (University of AmsterdamAmsterdam, Netherlands, 1999)
      In this chapter, Kenya's fishing industry is described. The chapter commences with an overview of the entire fishery sector in the country and follows this with a detailed analysis of the fisheries of Lake Victoria, the subject of this study. In presenting an overview of the country's entire fishing industry, we seek to show that despite the sector's small contribution to the gross domestic product (GDP), it is a significant source of livelihood and employment for many Kenyans. The dominance of Lake Victoria fisheries in the industry is emphasised as a justification for the choice of these fisheries as the subject of the research. To motivate the subsequent analysis, the factors responsible for biodiversity loss in the Kenyan fisheries of Lake Victoria are discussed in detail. The chapter, in addition, presents a comprehensive analysis of fish marketing and pricing and their socio-econo-environmental effects. Since fish is a nutritionally rich food, we assess its position, relative to other foodstuffs, in the country's national food policy. Existing literature and data, together with the micro-data obtained from the survey described in Chapter 2, are used.
    • Coral Assemblage Structure in Mombasa Marine National Reserve in Kenya, East Africa: A comparison between unfished areas and areas exposed to traditional fishing.

      Brydolf, Johanna (University of Stockholm, 1999)
      A study was carried out on a fringing reef in Mombasa Marine National Park & Reserve (MMNP&R) situated on the Kenyan coast in East Africa. Assemblage structure of 15 species and genera of scleratinian corals were assessed in terms of coral cover and species/genera distribution and abundance. Observations were made along line transects in both the park area and in the reserve area. Both areas are protected from coral collection and the park is also protected from fishing. In the reserve, however, traditional fishing is allowed. Results show a clear difference in the measured parameters between the strictly protected, unfished marine park area and the adjacent less protected marine reserve area. Coral cover and species/genus distribution and abundance were greater in the park than in the reserve. In all sites Porites constituted a significant part of total coral cover. All species had lower abundance in the reserve than in the park. Possible factors affecting the observed patterns are discussed.
    • Macrobenthos of Eastern African Mangroves: Life Cycles and Reproductive Biology of Exploited Species (MEAM) - Final Report INCO-DC: contract number IC 18-CT96-0127 (MEAM).

      Institute of Marine Sciences, University of Dar es Salaam, Zanzibar; University Eduardo Mondlane, Mozambique; University Of Transkei (Unitra), Umtata, South Africa; University Of Liverpool; Imar - University Of Lisbon; Museo Zoologico La Specola, University of Florence; Kenya Marine Fisheries and Research Institute (KMFRI) (Museo Zoologica "La Specola", Universita degli Studi di FirenzeFlorence, Italy, 2000)
      The MEAM objectives were: 1) to determine patterns in population structure, along a geographic gradient, of species selected for their commercial and/or ecological importance, by means of a standardised protocol to be developed within the project, 2) to study the growth. population structure and reproductive patterns of the above species, 3) to investigate the temporal pattern of larval release, 4) to analyse the behaviour of the pelagic larvae leading them to settle on the substratum, 5) to study the genetic flow between several coastal populations of a key species, in order to evaluate its interpopulation migratory effect, 6) to identify the relationships between the macrobenthic species and, more generally, the mangrove ecosystem and human activities. At different levels, all the MEAM objectives were fulfilled: 1) a technique of visual census of macrofauna was designed and repeatedly tested, providing comparable results independently of the observer and locality; for the first time, there is a simple method that permits any type of monitoring and ecological survey to be comparable in time and space. Validation coefficients (between 50% and 80%) are also available to correlate the census results with the actual animal density. From stomach content analysis, we could prove that, all along the East African coast, Scylla serrata, one of the most commercially important species, spends most of its time within the mangroves, feeding on macrobenthic species. In contrast, several important prawn species were only found as juveniles; thus for them, mangroves act as a nursery. In both cases, the importance of a healthy mangrove system is the basis for a sustainable management of the stocks of these species. 2) For the first time, we are able to compare the reproductive cycles of different species. Different patterns appear to dominate decapod life: periodic breeding can be found (i.e. Uca vocans), together with both semi-lunar and lunar periodicity; the latter is concentrated in a short period of the year (Neosarmatium meinertl), through most of the year with an interruption for the rainy season (i.e. Sesarma ortmanni) or throughout the year (i.e. U. annulipes). Due to the accurate and synchronous sampling strategy, we can for the first time ensure that the different reproductive patterns actually concern the basic biology of the species and not just latitudinal, geographical, or micro-climatic variations. 3) The results indicate a universal pattern of semi-lunar release centred on post-crepuscular ebbing tides and they allow us to generalise patterns of release for mangroves, namely the cyclic character of the reproductive timing and its relation to the major environmental cycles. 4) Patterns of larval fluxes and settlement in mangrove areas were described and they show a universal character: most species in mangroves will export their newly hatched stages to adjacent neritic water masses where they undergo most of their larval development. Return migration is accomplished by megalopa stages, and our results indicate an interaction between deterministic (cycles of tidal amplitude) and stochastic (wind stress) factors in the recruitment success of the different species. 5) We studied about 530 bp (base pairs) of the mitochondrial DNA cytochrome oxidase subunit I (mtDNA COl). The results indicate that gene flow is unexpectedly low and suggest that a population structuring is currently occurring. In order to prevent inappropriate S. serrata resource exploitation, it is advisable to refer to the local population as the appropriate short-term management unit. 6) The relationship between human activities and the mangrove ecosystem proved to be quite different among the three study sites: mainly timber cutting - mostly illegal - in Kenya; charcoal activity in Zanzibar; artisan fisheries and small-scale gathering in Mozambique. Where mangroves are seriously threatened (Kenya and Zanzibar), our detailed enquiries showed that people are well aware of the ecological and geo-morphological importance of mangroves. Nevertheless, due to the lack of alternative sources of revenue, they will not easily refrain from their destructive activities. Eco-tourism or similar activities are not seen as adequate alternatives, while cattle breeding or increased coconut cultivation could be. Unfortunately, both of these activities are limited by the lack of financial investment (cattle) or available land (coconuts).
    • Suspended sediment transport and exchange in Port Reitz Creek with special focus on the mangrove fringed Mwache wetland, Kenya.

      Kitheka, Johnson U. (Goteborg University, 2000)
      This study deals with dynamics of water exchange and sediment flux in the 17 Km super(2) mangrove-fringed Mwache wetland in Kenya. The study was implemented in the period between March 1998-March 1999. The creek experiences semi-diurnal tides with a spring tidal range of 3m. It receives freshwater only in rainy seasons, mainly from Mwache and Bome rivers whose total catchment area is 1900km super(2) and river discharge is less than 10m super(3)/s in normal rainfall years. There is usually no river discharge in dry seasons. The aim of the study was to determine the influence of tidal circulation on sediment transport in mangrove fringed creek systems. The study involved measurements of suspended sediment concentrations (SSC), salinity, temperature, current velocities and sea levels both in the tidal channels and in the mangrove swamp forest. Long-term SSC, sea level and current velocities were measured with an Orbital Backscatter Sensor, Micro Tide pressure gauges and a SD-6000 current meter respectively. A pressure gauge connected to a Backscatter sensor was also used to measure SSC along the creek. In addition SSC were determined by filtering water samples drawn from different levels of the water column with a Hydrobios water sampler. Water temperatures and salinities were measured in situ using an Aanderaa Salinity-Temperature sensor. The results show that the SSC is higher in the upper mangrove fringed creeks and lower in the frontwater zones bordering the Indian Ocean. The mean near surface SSC in the upper mangrove region is 0.16 g/l. while that in the lower region is 0.03 g/l. Near bottom SSC (in the upper zone) were usually higher and reached 1.40g/l. In the lower frontwater zones, the near bottom SSC was of the order 0.10g/l. At the creek entrance, the mean tidal volume fluxes in spring and neap is 2233 m super(3)/s and 937 m super(3)/s respectively. The (near bottom) mean tidal suspended sediment fluxes in spring and neap are 1220 Kg /s and 400 Kg/s respectively. The tidal sediment flux during flood tide ranged from 460 to 1740 Kg/s as observed at a cross-section near the entrance of the creek. The ebb ones were much lower being in the range 330-690Kg/s. Major resuspension of bottom sediments which raises SSC to values higher than 1.0 g/l, occurs only during flood tide at spring when the current velocities reach 1 m/s or more. The turbidity maximum zone (TMZ) with the highest SSC occurs in the upper middle region of the creek (Stn 3-6) where SSC is in the range 0.07-0.16 g/l. This zone coincides with the salinity maximum zone (SMZ) with salinity in the range 36-38 in the dry season. Calculations using formulas for erosion and deposition within the main tidal channel for the period between 15 and 23 February 1999 showed that erosion reach 6.0 x 10 super(-4) Kg/m super(2)/s while deposition reach 5.0 x 10 super(-5) Kg/m super(2)/s. Erosion dominates during periods of high current velocities and deposition during periods of low current velocities, which occur at low and high waters. A coarse comparison between total sedimentation and river sediment supply indicates that most of the riverborne sediments are trapped within the creek. In dry season with low sediment supply from the rivers, sediments are imported into the creek from Kipevu basin. Sediments re-suspended during spring flood tide enter the mangrove swamp where they are trapped due to the dense mangrove vegetation and sluggish current velocities of the order 0.05 g/l in the mangrove swamp. Sedimentation rate in the mangrove swamp is of the order 250 g/m super(2) per spring tide, corresponding to an accretion rate in the mangroves of the order 30 cm/100 years. This is higher than the estimated local sea-level rise of 22 cm/100 years, implying that Mwache mangrove swamp is keeping up in pace with sea level rise.
    • The Impact of Human Activities on the Ephibenthic Bivalve Community in Protected and Unprotected Marine Areas at the Kenyan Coast

      Boera, Priscillah N. (Moi University, 2001)
      A comparative survey of bivalve fauna found in reef flat, sea grass zones and shallow lagoons «2m) was undertaken in protected and unprotected marine areas to determine the density, diversity and species richness and the possible impacts of human activities on these mollusks. Data was collected by laying 3 transects of 400m2 in each site at the three areas. All bivalves observed were identified, their shell lengths measured and evidence of any kind of human interference recorded. Data was analyzed through use of species richness, diversity and similarity indices, coefficients of dispersion and covariance. These parameters were used to compare and describe species composition at each study site. Human activities were expressed in percentage frequencies of occurrence. The most prevalent human activity was then used to show the impact on the most vulnerable bivalve species A total of 17 bivalve species belonging to 13 families were observed in both the protected and unprotected areas of the Kenya coast from Oct. 1997March 1998. Their distribution showed low densities (2 bivalves/m2), low diversity (1.26 ± 0.005) in species composition and distribution (0.06475 ± 0.03) in the different substrate types. Modiolus auriculatus (0.473 ± 0.02) and Pinna muricata(0.45 ± 0.03) were the most prevalent. There was a significant difference in species diversity between Malindi and Mombasa reef flats at P<0.10. Shallow lagoons had very low relative density (0.49 ± 0.05) and diversity (0.068 ± 0.022) as compared to that of the reef flat which exhibited the highest density of (0.691 ± 0.017). This was attributed to the high deposits of shell, coral, and sand. Species composition classified up to family level showed Mitilidae (54% ad 44%) as the most represented in Kanamai and Malindi areas respectively; and Pinnidae (36%) in Mombasa. Abundance similarities were low (65 %) but for the lagoon (86.9%) and reef flat (90.0%) of Mombasa. Most bivalve species were clumped together (11421) or uniformly distributed (0- 0.395), with a few showing random distribution (1). Swimming, goggling/ SCUBA diving, walking/ trampling and turning of rocks were identified as the main forms of human activities causing disturbance. Frequencies of occurrence of these activities varied in the three areas with Kanamai exhibiting the highest. Results showed that the distribution of bivalve fauna in the protected and unprotected areas is bivalve density independent and not only influenced by human activities and management strategy but by other biological and environmental factors such as substrate type, tide range and wave activity. Human activities however affect those bivalves with fragile shells such as P. . muricata, through trampling resulting in injury and / or death. Therefore decentralisation of human activities within the marine parks is recommended to reduce their impacts. These activities can be carried out in the reserves. Beside marine protected areas are insufficient alone as they are not isolated from other critical environmental impacts and thus should' be complemented with strong conservation efforts outside the parks.
    • Comparison or damage caused by beach seining vs. corallivory on coral transplants in Mombasa, Kenya.

      Cros, Annick (University of Newcastle upon Tyne, 2001)
      Two coral species were transplanted into three distinct management areas adjacent to the Mombasa Marine National Park, Kenya: a no fishing MPA a gear restricted reserve with no beach seining, and a reserve with beach seining. Corallivory from fish or breakage from beach seining were measured by percentage mortality of transplants. The branching species, Porites cylindrica was more susceptible to disturbances than the massive species Porites lutea which showed no difference in mortality rate between the three sites. Branching Porites were more affected by corallivory than by beach seining or by restrictive gear fishing. Corals transplanted into the gear restricted fishing site had the highest survival, although in the past, this site has shown signs of overfishing and phase shifts towards a sea urchin dominant community. Branching coral transplants suffered the most damage inside the no fishing MPA, however, in the long term corals may suffer more in the two other areas through direct impact by beach seining and indirect impacts from overfishing. Extended experiments of longer duration should be conducted to differentiate between long and shon term effects and the rates of recovery for each management strategy.
    • An Empty Sufuria: The Effects of a Marine National Park on the Livelihood Strategies and Income Diversification of Fisherman Households at the Kenya Coast.

      Versleijen, Nicole (Wageningen University, 2001)
      This study was carried out in the districts Kilifi and Malindi. It focusses on the activities of artisanal fishermen and their households: the livelihood strategies they have, their attitude towards conservation, their indigeneous environmental conservation practices and the effects of the Watamu Marine National Park on these. In this study, data were collected through semi structured questionnaires, participant observation, life and career histories, network analysis and genealogies in Uyombo, Takaungu and the Watamu Marine National Park. Discussions were also held with the fishermen, Kenya Wildlife Service employees and people employed at the Watamu Marine National Park. In order to analyse the findings, an actor oriented approach is used, combined with the theories of political ecology and legal pluralism. By using these theories attention is paid to the historical background, wider context, human agency, property rights and community based natural resource management. The study revealed that fishermen are aware of the degradation of marine resources but are unable to do something about it because of their poor situation. Due to their declining standard of living people start to diversify. Two types of diversification can be found: fishermen who diversify by starting to cultivate on a shamba and farmers who diversify by starting to fish. Because of this, people of other ethnicities and religions, than those of the traditional fishermen started fishing. This ended indigeneous ways of conservation. Finally the study revealed that many fishermen are willing to stop fishing. However, the lack of employment possibilities will probably only drive more people to fishing, causing more severe degradation of marine resources. The thesis ends with some recommendations which might attribute to a decline of the degradation of marine resources and the deteriorating situation of fishermen at the Kenya Coast.
    • Ecology and Restoration of Mangrove Systems in Kenya.

      Kairo, J.G. (Vrije Universiteit Brussel, 2001)
      Chapter 1 presents a global picture of mangroves, what they are, their value, threats and efforts being made to address the problems. Mangroves once occupied 75% of the tropical coasts worldwide (McGill, 1959), but anthropogenic pressures have reduced the global range of the forests to less than 50%. Mangrove forests in Kenya are estimated to occupy about 54,000 ha, 70% of which occurs in Lamu district. There are 9 recorded mangrove species in Kenya. Chapter 2 provides a description of the study area -- the Kenyan coast. The coastline runs for approximately 574 km in a NNE and SSE direction, between latitudes 1~'40'S and 4~'25'S and longitudes 41~'34'E and 39~'17'E, The agro-climatological zones along the Kenyan coast differ markedly from the north to the south. The relative humidity is higher in the south than in the north. These differences in climate and ocean currents cause a strong divide between the vegetation types such that the northern mangroves in Lamu are structurally more complex than the southern mangroves in Mida creek. Chapter 3 details mangroves of Mida creek, defined in this study as young secondary mangrove stand that is vigorously growing, but subjected to periodic harvest. While we may be contented with the good natural regeneration that has taken place in Mida, close analysis reveals that Mida mangroves are in fact degenerating. What was harvested is not what is coming up. Mangrove harvesting in Kenya proceeds in a selective manner. Rhizophora mucronata is the preferred mangrove species because it produces poles that are hard, tall and straight. The most merchantable pole size is the boriti, with butt diameter range of 11.0-13.5 cm. Others are mazio (diameter 7.5-11 cm) and pau (5.0-7.5 cm). Poles greater than 15.0 cm diameter (banaa) are of less economic value and are therefore left standing in the forest. Excessive removal of boriti and mazio sized poles has created complex mangrove silvicultural problems in Kenya. The overgrown banaa canopy shade out juveniles and young trees and cause them to be crooked as they try to grow in an open space inside the closed forest canopy. In open canopy areas, the less preferred Ceriops seedlings are regenerating at the expense of the removed Rhizophora trees. Chapter 4 is about the application of remote sensing and GIS technology in mapping the mangrove forests within and adjacent to the Marine Protected Area (MPA) of Kiunga, Lamu. The stand volume ranged from 6.85 m super(3)/ha to 710.0 m super(3)/ha. The average stand volume was 145.88 m super(3)/ha, which corresponds to a stocking rate of 1736 stems/ha. Given its high potential productivity and regeneration, mangroves within and adjacent to KMNR have excellent prospects for sustainable exploitation. The management of mangroves as renewable resources poses severe problems in that natural regeneration seems to be insufficient where large-scale operations have taken place. To sustain the yield of these forests there is a need to address both artificial and natural regeneration methods. Artificial mangrove planting in Asia has been promising in solving the problems of limited supply of mangrove products as well as maintaining the overall ecological balance of the coastal system. In Chapter 5, assessment is made of the above ground biomass increment of mangrove plantations that were established at Gazi bay in 1991. The above ground biomass of a 5-year old Rhizophora plantation was calculated at 20.25 t dry matter ha super(-1) for trees with stem diameter greater than 5.0 cm. Finally in Chapter 6, a comparative analysis of mangrove forests along the Kenya coast is provided. Emphasis is given to the mangrove areas where this study was done. The variation of mangrove forest structure in Kenya occurs due to differences in environmental settings as well as differences in the levels of human pressure. Mangroves north of Tana river are river and tidal dominated systems, with a lower human pressure than mangroves south of the Tana river.
    • Water Exchange and Circulation in Selected Kenyan Creeks.

      Nguli, Michael Mutua (University of Dar es Salaam, 2002)
      Tides, currents, salinities and temperatures were studied from 1995-1998 in three selected creeks on the Kenya coast (Gazi Bay, Tudor and Kilifi Creeks) in order to improve knowledge on circulation and water exchange between the creeks and the ocean. Locally available meteorological data, tide gauge data and historical cruise data were also analysed. A meteorological mast was used for detailed studies of sea surface heat fluxes. The studies were carried out focussing on the monsoon seasons; the Inter-Monsoon Long Rain (IMLR; April-May), the South East Monsoon (SEM; June-September), the Inter-Monsoon Short Rain (IMSR; October-November) and the North East Monsoon (NEM; December-March). Gazi Bay is open to the sea whereas Tudor and Kilifi Creeks have sheltered bays inside 2 deep and relatively narrow inlets. The creeks are similar in size (Area;::;15 106m ; volum~60 1Q6m\ Spring tidal ranges at the entrances were estimated at 3.01, 3.16 and 3.3m, respectively, with strong M2 dominance and form factors of about 0.2. The creeks are not restricted (sensu Kjerfve), but there are tidal asymmetries with ebb dominance in Gazi Bay and udor Creek. However, the innermost parts of Gazi Bay feature flood dominance with strongly restricted flows and long ebbing periods (78hrs during spring). The features are accompanied by large shallow water and fortnightly tides. Similar shallow water and fortnightly response is seen also in the upper parts of Tudor Creek but the asymmetry is of different origin. Here, the tide is ebb dominated, presumably because of baroclinic processes at the inlet, and the tidal range is larger (5%) than in the ocean. In Gazi Bay the range is lowered by 15%. The asymmetries in Gazi Bay and Tudor Creek are accompanied by phase lags of 15-120min, indicating progressive character of the tide. Kilifi Creek data indicated a pure standing wave character. Kilifi inlet is shorter and wider than that of Tudor Creek, which probably explains the difference. Tide gauge temperature data from all sites are evaluated using harmonic analysis. Clear response for semidiurnal, diurnal and fortnightly periods indicates possibilities to unprove calculations of water exchange. Water exchange between the creeks and the ocean wa determined from a seasonal, steady state heat budget using temperature data from hydrographic observations and net sea surface heat fluxes from climatology data. In Tudor Creek th residence time is from 3 days at spring to 7 days at neap and in Kilifi Creek from 2.5 days at spring to 6 days at neap. In Gazi Bay the corresponding spring and neap residence times are 1 and 2.5 days, respectively. Corresponding calculations based on salinity basically failed because we were unable to determine the river discharge with a good enough resolution. Temperature and salinity differences between the creeks and the open ocean, averaging ~T;::;l °c, ~S::::-O.3, were used study the impact of the coastal ocean waters on the creek hydrography. These studies revealed interesting features, some of which are not foood in literature. There are two outstanding seasons, namely the late NEM (during February) and the IMLR (April/May) in between which rapid changes take place in the coastal waters. February is in the end of the dry season, dominated by excess evaporation and hypersaline conditions, May by strong rains estuarine conditions. In the ocean February is characterized by a low oceanic sea level, and a weak or occasionally nonexistent north-going EACC. The south-going Somali Current with high salinities may appear at the coast (even subducted). When the NEM weakens the situation changes; there is a rapid increase in the sea level and a decrease in salinity caused by rainfall at the onset of the IMLR We show a strong correlation between the steric height and seasonal development of the sea level. However, the interpretation suffers from too few ocean data. There is no clear whether the different seasons exert different effects on the water exchange. We expected the IMLR season to be more efficient in removing creek water, thus enhancing water exchange in comparison with the NEM because ofhigh current velocities. It seems as if this is the case, although the difference is small.