College of Agricultural Sciences and Fisheries Technology

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    Bivalves Fouling Floating Cages Used in Aquaculture
    (1972) Bwathondi, Philip O. J.; Ngoile, M.
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    Preliminary Investigation on the Rabbitfish, Siganus Canaliculatus in Tanzania
    (Elsevier, 1982) Bwathondi, Philip O. J.
    Preliminary investigation on the culture of Siganus canalicullatus in floating cages in Tanzania coastal water has revealed that the fish has high culture potential in the region. It is euryhaline, inhabiting areas where salinities range from 23‰ to 35.8‰. The fish grows faster on pelletted diets than on ordinary seaweeds. It is estimated that the fish would reach a marketable size of 20 cm fork length in 6 months; hence two crops can be harvested in a year.
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    Evaluation and Optimization of Sisal Harvesting Systems
    (1984) Shine, S. J.; Bhandari, V. K.; Majaja, Bashira A.
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    Anthropometric Data Collection of the Tanzanian Worker
    (1984) Majaja, Bashira A.; Bhandari, V. K.
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    Cutting of Sisal
    (1989) Majaja, Bashira A.; Chancellor, W. J.
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    Studies on the optimization of immobilising acetogenic and methanogenic biomass on polyurethane carrier
    (. Fac. Landbouw. Rijksuniv. Gent, 1989) Rubindamayugi, M.S.T.; Broeders, P.; op den Camp, H.J.M.; Lubberding, H.J.; Vogels, G.D.
    The influence of operational conditions (including the specific substrate concn in the feed, the hydraulic retention time and wastewater composition) on the rate of immobilization of acetogenic and methanogenic bacteria in an anaerobic polyurethane carrier reactor (PCR) treating synthetic Volatile Fatty Acids (VFA) based wastewater was investigated. The performance of continuous and fed batch culture reactor systems had a roughly similar start up period and biogas production rate. Preliminary results indicated that these systems started up within 8 d of operation. A max. concn of 151 mM acetate and 126 mM propionate was applied in the reactors treating VFA based wastewaters with a higher proportion of acetate and propionate, respectively. In all reactors a max. concn of 45.4 mM butyrate was applied. At max. acetate concn no toxic effect on acetogenic and methanogenic biomass activity were observed. The max. propionate concn showed strong inhibitory effect on biomass activity. At the max. feed concn the VFA conversion, methane production rate and methane content decreased. Biomass activiy tests showed that the reactors fed with a higher acetate concn showed higher acetogenic and methanogenic activity than the reactor treating wastewater with higher propionate concn. The influence of operational conditions on biomass washout were also investigated.
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    Nearshore Fish Resources and Fisheries around Kigoma, Eastern Coast of Lake Tanganyika
    (1992) Ndaro, Simon G. M.
    The fish habitats along an inshore water stretch along the eastern/central coast of Lake Tanganyika are discussed and a quantitative analysis of the species composition, distribution and abundance of the littoral fishes within the area of study is presented. Seventy-one species of fish belonging to 48 genera and to 15 fish families were collected and identified during the study. The majority of species belonged to the Cichlidae family. Intensive beach seining for clupeids is suggested as one of the causes of low fish biomass in the area surveyed. The areas south of Kigoma appeared to contain more fish, with average catch rates of 11.7 kg/haul than those north of Kigoma where average catch rates of 7.6 kg/haul were recorded. Some suggestions for improved management of these resources are given.
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    Physical Processes in the Rufiji Delta and Their Possible Implications on the Mangrove Ecosystem
    (Springer, 1992) Francis, Julius
    The physical processes such as coastal currents, estuarine circulation and monsoon winds prevailing in the Rufiji delta are discussed. The relationship between these processes and the occurrence of long-term trapping of the river discharge and the outflow of waters from the mangrove swamps into the nearshore zone has been observed. The trapped waters in the nearshore zone significantly reduce the mixing between the estuarine and offshore waters, leading to the two waters having distinctive properties. The existence of the trapped waters in the nearshore zone is supported by evidence from a satellite image and aerial photograph and measurements of salinity and suspended sediment concentration. The trapping phenomenon is discussed in the light of its possible implications on the ecology of mangrove ecosystems. Trapping may explain the enhanced growth of the mangrove in the delta compared to other areas. This trapping effect may be providing more time for nutrient retention in the mangrove zone, incorporation of the decomposed leaf litter and fine sediments in the substrate, and settling of fruits and seedlings in the swamps, thereby enhancing the regeneration of the mangrove.
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    Anthropogenic Pollution in the Dar es Salaam Harbour Area, Tanzania.
    (Elsevier, 1992-11) Machiwa, John F.
    Man-made pollutants, namely, petroleum hydrocarbons, polychlorinated biphenyls (PCBs), and heavy metals as well as microbial pollution in the sediments of the harbour channel have been evaluated. Petroleum hydrocarbons, PCBs and heavy metals (Fe, Pb, Cu, and Zn) are at elevated levels in the port area used for loading and unloading activities. The concentration of the chemicals decreases further offshore, with the exception of cadmium which, surprisingly, is enriched in the sediments at the ship outer anchorage zone. The concentration-depth profile of the sediment core samples show that in general metals are uniformly distributed with depth in the sediment. The between station variation of Mn, Cr and Ni is strongly influenced by grain size differences. Total and faecal coliform bacteria are few in the port area but are extremely abundant at the fish landing beach and close to the sewer outfall
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    Novel Nitrogen Sources for Growth of Bacillus Fastidiosus and their Effect on the Activity of NADP-Dependent Glutamate Dehydrogenase
    (1993) Muruke, Masoud S. H.; den Camp, Huub J. M. O.; van der Drift, Chris
    Although Bacillus fastidiosus assimilates ammonium formed internally during growth on urate, allantoin or allantoate via NADP-dependent glutamate dehydrogenase (NADP-GDH), growth on exogenous ammonium as nitrogen source has not been observed. Growth on ammonium, urea and ureidoglycolate, intermediates of the urate degradative pathway, was found to occur if the mineral growth medium containing glycerol as a carbon source was supplemented with both allantoin (0.5 mM) and brain heart infusion (BHI, 0.1%, w/v) or yeast extract. Neither allantoin nor BHI supported growth alone or in combination unless ammonium was present. NADP-GDH activity appeared to be regulated only by the extracellular concentration of allantoin or allantoate. Enzyme activity was not influenced by other nitrogen sources or the intracellular ammonium concentration.
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    The Status of the Fishery Resource in, the Wetlands of Tanzania
    (1993) Bwathondi, Philip O. J.; Mwamsojo, G. O. J.
    The main types of wetlands in Tanzania are described as an introduction to a coverage of the fisheries of the large lakes, the minor waters, the rivers and the intertidal ecosystems. Fisheries potential is estimated and details of catches for each wetland type are given. Fishing techniques and the future of the fisheries are discussed and recommendations made for future wetlands fishery conservation.
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    Effects of Intensive Seaweed Farming on the Meiobenthos in a Tropical Lagoon
    (Elsevier, 1995) Olafsson, Emil; Johnstone, Ron W.; Ndaro, Simon G. M.
    Open water aquaculture of the seaweed Eucheuma spinosum, imported to Zanzibar from the Philippines in 1989, is presently a large scale operation on the island, with algal farms covering around a 1000 ha of the intertidal area. To assess the effects of the farming on benthic communities both field and laboratory studies were conducted. Two field studies conducted at different times showed that all major meiofaunal taxa were found in significantly lower numbers within the farm area compared with control areas. Multidimensional scaling ordination of nematode species, genera and family abundance data separated samples from farmed and control areas. There was a significant difference in the nematode assemblage structure among areas in pairwise comparisons using ANOSIM. The trophic structure of the nematode assemblage was characterised by a high number of epistrate feeders in all areas ranging from 73 to 96% of total numbers in the samples. To test the hypothesis that toxic substances excreted by the seaweed were responsible for lower abundance inside the farm area, a laboratory experiment was conducted. Eucheuma plants were added to several microcosms and allowed to grow there for 40 days. The results indicated no effects of the seaweed on the density of the major infauna taxa as no significant difference was found among the treatments. It is concluded that other factors such as increased predation by benthic feeding fish and the mechanical disturbance of the sediments may better explain the observed differences in infauna abundance inside and outside the algal culture farms.
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    Small-Scale Variation in Major Meiofaunal Taxa and Sediment Chemistry in Tropical Sediments
    (1995) Ndaro, Simon G. M.; Sjoling, S.; Olafsson, Emil
    Variations in sediment biochemistry and abundance of meiofauna were investigated in three tropical habitats: mangrove forest, intertidal lagoon, and subtidal reef area in eastern Africa. Both the biochemical components of the pore water and the meiofauna varied substantially over small distances in all three habitats. In the mangrove area, the color of the pore water was found to be positively correlated with the major meiofaunal taxa, especially the nematodes. In the coastal lagoon, polychaetes showed negative correlation with particulate organic matter while other groups showed no correlation with any of the chemical components analyzed. In the subtidal reef area no chemical components were found to correlate with the meiofauna. When data from the three habitats are taken together two clear associations emerge. First, grain size shows a highly significant relationship with both total fauna and nematode numbers. Second, there is clear association between the amount of particulate organic carbon and particulate organic nitrogen in the pore water.
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    The Level of Enzymes Involved In the Allantoin Metabolism of Bacillus Fastidiosus Grown under Different Conditions
    (Springer Link, 1995) Muruke, Masoud S. H.; den Camp, Huub J. M. O.; Semesi, Amelia K.; van der Drift, Chris
    Bacillus fastidiosus was cultivated in batch and continuous culture on various carbon and nitrogen sources. The enzymes involved in allantoin degradation (allantoinase, urease, carboligase) of B. fastidiosus were hardly affected by either carbon or nitrogen source. In contrast, the enzymes involved in glycerol utilization (glycerol kinase, glycerol 3-phosphate dehydrogenase) were induced during growth on glycerol, but were not affected by the amount of allantoin present.
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    The effects of size grading and stocking density on growth performance of juvenile abalone
    (Elsevier, 1995-11-15) Mgaya, Yunus D.; Mercera, John P.
    The effects of size grading and stocking density on the growth of juvenile European abalone, Haliotis tuberculata L. (Gastropoda: Haliotidae) were assessed in the hatchery. Animals were held in cages deployed in a flowtray with recirculating seawater maintained at 18 ± 2 °C, and fed ad libitum on the red alga Palmaria palmata (L.) Kuntze. In the grading experiment juvenile abalone were divided into four populations consisting of small (mean ± s.e; initial shell length = 15.3 ± 0.15 mm; n = 35), medium (initial shell length = 19.6 ± 0.16 mm; n = 35), large (initial shell length = 23.8 ± 0.17 mm; n = 35) and an ungraded control group (16.8 ± 0.41 mm; n = 35). Rearing was carried out over a period of 226 days, after which it could be concluded that an advantage in overall growth performance had been gained by grading the animals. There was evidence that growth of small abalone improved in the absence of larger conspecifics. In the stocking density experiment with two size grades and three stocking densities, a decreasing exponential relationship was found between growth (body weight and shell length) and stocking density, with a substantial amount of growth occurring at all densities. Final total biomass for both grades of abalone increased with density. For the smaller grade biomass gain increased as density increased. However, for the larger grade biomass gain declined at higher density. Overall mean survival (± s.e) was 98.3 ± 0.4% and was not influenced by density. It is suggested that the choice of stocking density is essentially a trade-off between maximum growth, optimal biomass gain, and economic considerations which may dictate densities that would result in a net reduction in overall production costs.
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    Flora and Crabs in a Mangrove Forest Partly Distorted by Human Activities, Zanzibar.
    (Elsevier, 1995-12) Machiwa, John F.; Hallberg, Rolf O.
    A preliminary study on flora and fauna in a disturbed mangrove ecosystem is presented. The zonation of mangrove flora in the forest is clearly displayed by two dominant species, Avicennia marina and Sonneratia alba. A. marina forms an almost pure stand at the terrestrial edge of the forest, but the species is ubiquitous in the area. S. alba almost exclusively occupies the marine fringe of the forest.