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  • 1.
    Amir, Omar A.
    et al.
    Stockholm University, Faculty of Science, Department of Zoology.
    Jiddawi, Narriman
    Berggren, Per
    Stockholm University, Faculty of Science, Department of Zoology.
    The occurrence and distribution of dolphins in Zanzibar, Tanzania, with comments on the differences between two species of Tursiops2005In: Western Indian Ocean journal of marine science, ISSN 0856-860X, Vol. 4, no 1, p. 85-93Article in journal (Refereed)
    Abstract [en]

    Incidental catches (bycatch) in gillnet fisheries off Zanzibar (Unguja Island), as asource of mortality among several species of dolphins, were reported in a questionnaire surveyconducted in 1999. As a follow-up to that survey, from January 2000 to August 2003, wemonitored the incidental catches of dolphins collected from 12 fish landing sites. Six species ofdolphins were recorded from 143 specimens retrieved from bycatches in drift- and bottom setgillnets. Of these, 68 (48%) were Indo-Pacific bottlenose dolphins (Tursiops aduncus), 44 (31%) spinner dolphins (Stenella longirostris), 12 (8%) Risso’s dolphins (Grampus griseus), 11 (8%) Indo-Pacific humpback dolphins (Sousa chinensis), 6 (4%) Pan-tropical spotted dolphins(Stenella attenuata) and 2 (1%) common bottlenose dolphins (Tursiops truncatus). Most of thebycatches (71%) were in nets set off the north coast of Unguja Island. In this paper, bycatchrecords are examined to describe the occurrence and distribution of dolphin species in UngujaIsland coastal waters. The relatively large numbers of bycatch dolphins recorded indicate thatbycatch may be a potential threat to local populations that need to be addressed in futureconservation and management efforts in the region.

  • 2.
    De La Torre-Castro, Maricela
    et al.
    Stockholm University, Faculty of Science, Department of Systems Ecology.
    Eklöf, Johan
    Stockholm University, Faculty of Science, Department of Systems Ecology.
    Rönnbäck, Patrik
    Stockholm University, Faculty of Science, Department of Systems Ecology.
    Björk, Mats
    Stockholm University, Faculty of Science, Department of Botany.
    Seagrass importance in food provisioning services: fish stomach content as a link between seagrass meadows and local fisheries2008In: Western Indian Ocean journal of marine science, ISSN 0856-860X, Vol. 7, no 1, p. 95-110Article in journal (Refereed)
    Abstract [en]

    The links between ecosystem processes and functions and ecosystem services (i.e. the humanbenefits from those) are elusive. In this paper, the food provisioning service of seagrass meadows isoperationalized through the study of the stomach contents of 13 important commercial fish species inChwaka Bay, Zanzibar. Using local fishers’ knowledge on bait, scientific knowledge about the structureof the meadows (associated flora and fauna), stomach content analysis and multivariate statistics, the foodprovisioning service associated with seagrasses and its importance for fish (as important diet component)and for humans (in small-scale artisanal fisheries) are described. The study presents the food items for 13commercial fish species identified at the lowest possible taxonomical level and compares with previousliterature findings. In addition, differences in stomach contents of Siganus sutor and Leptoscarus vaigiensiscaught with both drag-nets and dema basket traps are investigated in order to explore bait presence andindirectly evaluate fishers’ knowledge on bait preference. The results show that most of the items consumedby commercial fishes are associated with seagrass beds and that there are clear indicators that the baittraditionally used seems to be effective. The paper elaborates on the consideration of seagrass ecosystemsin a holistic perspective, the difficulties in valuation of ecosystem services and finally the crucial importanceof these aspects for human well-being and sustainability in coastal communities of the Western IndianOcean.

  • 3.
    Hamisi, Mariam
    et al.
    Stockholm University, Faculty of Science, Department of Botany.
    Lyimo, Thomas
    University of Dar es Salaam, Tanzania.
    Cyanobacteria Occurrence and Nitrogen Fixation Ratesin the Seagrass Meadows of the East Coast of Zanzibar: Comparisons of Sites With and Without Seaweed Farms2008In: Western Indian Ocean journal of marine science, ISSN 0856-860X, Vol. 7, no 1, p. 45-55Article in journal (Refereed)
    Abstract [en]

    The occurrence and biological nitrogen fixation rates of epiphytic and benthic diazotrophs were studied in seagrass meadows at sites with seaweed farms and at a control site without seaweed farms from two locations, Chwaka Bay and Jambiani, along the east coast of Zanzibar. Ten species of cyanobacteria were encountered and Lyngbya majuscula and Microcoleus sp. were dominant in Chwaka Bay and Jambiani respectively. Cyanobacterial occurrence was significantly higher in seagrass meadows without seaweed farms (P<0.02), but there was no significant difference (P>0.05) in biomass (chlorophyll a). Biomass averaged 2.96±0.73 and 3.10±1.24 μg Chl a cm-2 in seaweed farms and 3.46±1.72 μg Chl a cm-2 at Chwaka Bay and 3.14±1.31 μg Chl a cm-2 at Jambiani in transects without seaweed farms. Nitrogenase activity showed no significant differences between sites with and without seaweed farms, (P=0.66 Chwaka and 0.75 at Jambiani). Fixation rates in sites without seaweed farms averaged 35.8±39.9 (Chwaka Bay) and 13.1±12.7 (Jambiani) μmol of C2H4 produced/m2/hr, while with seaweed farms averaged 22.6±22.5 and 12.8±14.9 μmol C2H4 produced/m2/hr at the same sites. There were no significant differences in nutrient levels between locations, sites with and without seaweed farms, or between tidal levels except for nitrate, which was significantly higher (P=0.01) at Jambiani than at Chwaka Bay. It was concluded that diazotrophs contribute a significant amount of exogenous nitrogen to the seagrass ecosystem, but no significant differences could be found between sites with or without seaweed farms.

  • 4.
    Henriksson, Oskar
    et al.
    Stockholm University, Faculty of Science, Department of Zoology, Animal Ecology. Södertörns högskola.
    Mwandya, Augustine
    Gullström, Martin
    Stockholm University, Faculty of Science, Department of Ecology, Environment and Plant Sciences.
    Thorberg, Marika
    Grahn, Mats
    AFLP assisted DNA-Barcoding of mullets (Mugilidae) used in East African aquaculture2012In: Western Indian Ocean journal of marine science, ISSN 0856-860X, Vol. 11, no 1, p. 41-54Article in journal (Refereed)
    Abstract [en]

    There is a growing demand for wild caught juvenile fish to supply the market for aquaculture. However, little is known about the genetic effects of juvenile collection from wild populations. There are a number of imminent threats to both aquaculture systems and wild fish populations. Juvenile collection from a single population can for example reduce population’s evolutionary potential as well as the disease resistance within an aquaculture pond. In this study, we investigated the local genetic structure of juvenile mullets collected from five sites around Bagamoyo (Tanzanian mainland) and Zanzibar Island, East Africa. Fish were caught in low tide using a seine net. The fish were morphologically identified, and then genetically identified using direct sequencing of the CO1 gene with cross referencing with the Barcode of Life Database (BOLD) systems.  Molecular variance analyses were used to infer genetic subdivision based on geographic sampling site as well as inferring population structure through the Bayesian assignment test implemented in STRUCTURE 2.3. Our results showed that samples morphologically identified as Mugil cephalus where in fact Valamugil buchanani and we also found evidence of an introgression genome event, where the gene flow from one species may have affected the general gene pool. The Bayesian analysis revealed a clear genetic population structure among the sampled fish; the main difference was the presence of a unique mainland cluster. Our findings may have important implications for management and conservation of mullet fishes in the region and elsewhere.

  • 5.
    Macia, Adriano
    Stockholm University, Faculty of Science, Department of Systems Ecology.
    Juvenile Penaeid shrimp density, spatial distribution and size composition in four adjacent habitats within a Mangrove fringed bay on Inhaca island, Mozambique2004In: Western Indian Ocean journal of marine science, ISSN 0856-860X, Vol. 3, no 2, p. 163-178Article in journal (Refereed)
  • 6.
    Macia Júnior, Adriano Afonso
    Stockholm University, Faculty of Science, Department of Systems Ecology.
    The primary carbon sources for juvenile penaeid shrimps in a mangrove-fringed bay at Inhaca island: A dual carbon and nitrogen isotope analysis2004In: Western Indian Ocean journal of marine science, ISSN 0856-860X, Vol. 3, no 2, p. 151-161Article in journal (Refereed)
  • 7.
    Mamboya, Florence
    et al.
    Stockholm University, Faculty of Science, Department of Botany.
    Semesi, A
    Mtolera, Matern
    Pratab,
    Björk, Mats
    Stockholm University, Faculty of Science, Department of Botany.
    Accumulation and physiological effects of copper and zinc on the brown macroalga Padina boergesenii.2007In: Western Indian Ocean journal of marine science, ISSN 0856-860X, Vol. 6, no 1, p. 17-28Article in journal (Refereed)
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