Browsing by Author "Tsotsobe, Sakhile Vincent"

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    Temporal and spatial variability in copepod abundance, distribution and community structure off Walvis Bay in the northern Benguela Current, 1979-1981
    (University of the Western Cape, 2005) Tsotsobe, Sakhile Vincent; Gibbons, M.J; Verheye, H.M
    The zooplankton samples used for retrospective analysis in this study form part of the historical SWAPELS (South West African Pelagic Egg and Larva Survey) collection from January 1972 to December 1989, which covered the entire Namibian shelf. The SWAPELS Programme was initiated following the collapse of the Namibian sardine fishery during the late 1960s and early 1970s. This study investigates variability in the temporal and spatial distribution of total zooplankton (non-gelatinous) biomass, total copepod abundance, as well as copepod community structure off the coast of Walvis Bay along, primarily, transect 70 (23° S), and secondarily, transects 66 (22°67 S) and 74 (23°33 S), over the period 1979- 1981. Included in the data set are sea surface temperatures (SSTs) and surface salinities, allowing for spatio-temporal trends in the hydrology of this region to be examined. Despite extensive variability in SST (1 1.27- 18.15 °C), the most frequently occurring SSTs were in the 15-16 °C range. In 1979 salinities ranged mostly between 35.1 and 35.2, whereas in 1980 and 1981 modal salinities fell within the 35.0-35.1 and 35.2- 35.3 ranges, respectively. A clear seasonal pattern in the cross-shelf distribution of SST and salinity was observed in 1979-80, when, generally, warm , high-salinity water covered most of transect 70 (23° S) in summer to early autumn. In spring the cool inshore water extended seaward, to recede again into summer. The existence of cool inshore surface water from mid-winter to mid-spring, warming up into summer and extending offshore, was indicative of a typical upwelling cycle off Walvis Bay.