Browsing by Author "Bwathondi, Philip O. J."

Now showing 1 - 7 of 7
  • Thumbnail Image
    Item
    Bivalves Fouling Floating Cages Used in Aquaculture
    (1972) Bwathondi, Philip O. J.; Ngoile, M.
  • Thumbnail Image
    Item
    Coupled Human and Natural System Dynamics as Key to the Sustainability of Lake Victoria’s Ecosystem Services
    (2014) Downing, Andrea S.; van Nes, Egbert H.; Balirwa, John S.; Beuving, Joost J.; Bwathondi, Philip O. J.
    East Africa’s Lake Victoria provides resources and services to millions of people on the lake’s shores and abroad. In particular, the lake’s fisheries are an important source of protein, employment, and international economic connections for the whole region. Nonetheless, stock dynamics are poorly understood and currently unpredictable. Furthermore, fishery dynamics are intricately connected to other supporting services of the lake as well as to lakeshore societies and economies. Much research has been carried out piecemeal on different aspects of Lake Victoria’s system; e.g., societies, biodiversity, fisheries, and eutrophication. However, to disentangle drivers and dynamics of change in this complex system, we need to put these pieces together and analyze the system as a whole. We did so by first building a qualitative model of the lake’s social-ecological system. We then investigated the model system through a qualitative loop analysis, and finally examined effects of changes on the system state and structure. The model and its contextual analysis allowed us to investigate system-wide chain reactions resulting from disturbances. Importantly, we built a tool that can be used to analyze the cascading effects of management options and establish the requirements for their success. We found that high connectedness of the system at the exploitation level, through fisheries having multiple target stocks, can increase the stocks’ vulnerability to exploitation but reduce society’s vulnerability to variability in individual stocks. We describe how there are multiple pathways to any change in the system, which makes it difficult to identify the root cause of changes but also broadens the management toolkit. Also, we illustrate how nutrient enrichment is not a self-regulating process, and that explicit management is necessary to halt or reverse eutrophication. This model is simple and usable to assess system-wide effects of management policies, and can serve as a paving stone for future quantitative analyses of system dynamics at local scales.
  • Thumbnail Image
    Item
    Effects of Elevated Carbon Dioxide and Temperature on Survival and Morphology of Japanese Whiting Sillago Japonica
    (2016) Yona, G.; Madalla, Nazael; Mwandya, Augustine W.; Ishimatsu, A.; Bwathondi, Philip O. J.
    The objective of the present study was to examine the effect of elevated CO2 and temperature on survival and morphology of Sillago japonica yolk sac larvae under the Institute for East China Sea Research (ECSER) Nagasaki, Japan. In this study, we examined hatching success, survival and morphology of the larvae of Sillago japonica under four conditions: control (C), seawater pCO2 382µatm, temperature 27 °C; high CO2 (HC), 915µatm, 27 °C; high temperature (HT), 385 µatm, 31 o C; and high CO2+high temperature (HCT), 932µatm, 31 o C. Fertilized eggs were obtained from broodstock reared in natural seawater, and transferred to experimental containers in each treatment. Hatched larvae were observed until the completion of yolk sac absorptions on 3 days post hatching (dph). The experiment was repeated four times with 4 replicates for each treatment in each experiment. Also, the temperature appeared to have exerted a stronger influence on hatching success (Hs) and larval survival (Sv): Hs and Sv at 3 dph were both significantly (p>0.05) depressed in HT (Hs 52.5±1.25%, Sv 23.8±4.38%) and HCT (Hs 51.3±3.13%, Sv 20.0±0.63%) treatments than in C (Hs 98.1±0.94%, Sv 74.4±2.03%) and HC (Hs 95.0±2.5%, Sv 49.7±3.44%) treatments. In contrast, CO2 was the predominant factor responsible for morphological abnormality: percentage morphological abnormality was significantly (p>0.05) higher in HC (15.8±2.72%) and HCT (41.0±10.86%) treatments than in C (0.4±0.65%) and HT (2.4±2.40%) treatments. Most individuals in HC and HCT treatments had body axis either curved or bent, with aberrant swimming behavior. These results indicate that projected future ocean environments will have significant negative impacts on hatching success, and larval survival and morphology of S. japonica, which might have serious ramifications for recruitment of the species. Comparative studies on other teleost and elasmobranch species are critically needed.
  • Thumbnail Image
    Item
    Mitogenomic Analysis for Coelacanths (Latimeria Chalumnae) Caught in Tanzania
    (Elsevier, 2007-04) Sasaki, Takeshi; Sato, Tetsu; Miura, Seiko; Bwathondi, Philip O. J.; Ngatunga, Benjamin P.; Okada, Norihiro
    In recent years, a large number of individuals of the species Latimeria chalumnae, one of the living fossil coelacanths, have been landed off the coast of Tanzania. Although L. chalumnae specimens have also been landed at other localities in the western Indian Ocean, so far, viable populations of this species have been identified only at two localities, Comoros and South Africa. Therefore, the recent active catch off Tanzania suggests a new habitat for L. chalumnae. To examine the genetic background of the Tanzanian fish, we analyzed complete mtDNA sequences of two Tanzanian individuals (Kigombe-9 and Songo Mnara-1) collected from the north and south coasts of Tanzania. Using the recently reported criteria for six haplotypes established in a population genetic study for coelacanths living in the western Indian Ocean [Schartl, M., Hornung, U., Hissman, K., Schauer, J., Fricke, H., 2005. Relatedness among east African coelacanths. Nature 435, 901.], we characterized Songo Mnara-1 as haplotype 1 and Kigombe-9 as haplotype 5. We suggest that the Songo Mnara specimen is a member of the Comoran group, but was swept away by the South Equatorial current. The individual from Kigombe may be a member of an undiscovered population that exists near the boundary between Tanzania and Kenya. Further analysis using more than 19 individuals recently captured off the north coast of Tanzania will reveal whether a new population exists there. Our sequence data suggest additional variable sites in the mtDNA sequence that may define the population structure of coelacanths in the western Indian Ocean and also raise the possibility that the previously published Comoran coelacanth mtDNA sequence contains several critical errors including base changes and indels.
  • Thumbnail Image
    Item
    Population Genetic Analysis of Western Indian Coelacanths Based on Mitochondrial DNA
    (2007) Okada, Norihiro; Sasaki, Takeshi; Bwathondi, Philip O. J.; Ngatunga, Benjamin P.
    In recent years, a large number of individuals of coelacanths have been landed off the coast of Tanzania. Although coelacanth specimens have also been landed at other localities in the western Indian Ocean, so far, viable populations of this species have been identified only at two localities, Comoros and South Africa. Therefore, the recent active catch off Tanzania suggests a new habitat for coelacanth. Based on the current situation surrounding the Tanzanian coelacanth, to examine the genetic background of the fish, we determined complete mitochondrial sequences of Tanzanian coelacanths collected from the north and south coasts of Tanzania. Using the criteria for six haplotypes established in a population genetic study for coelacanths living in the western Indian Ocean (Schartl et al., Nature 2005; 435:901), we analyzed mitochondrial haplotypes of Tanzanian coelacanths. As a result of haplotype characterization, we suggest that the southern specimen is a member of the Comoran group, but were swept away by the South Equatorial current. On the other hand, some of the northern specimens formed a haplotype group that contains Kenyan coelacanth. We assumed that the north Tanzanian specimens may be a member of an undiscovered population that exists near the boundary between Tanzania and Kenya.
  • Thumbnail Image
    Item
    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.
  • Thumbnail Image
    Item
    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.