Articles by Author: Fj Keulder Stenevik

Search results for Fj Keulder Stenevik

We found 9 results for you
  1. When plenty is not enough: an assessment of the white stumpnose (<em>Rhabdosargus globiceps</em>) fishery of Saldanha Bay, South Africa

    When plenty is not enough: an assessment of the white stumpnose (<em>Rhabdosargus globiceps</em>) fishery of Saldanha Bay, South Africa

    Item type: Journal Article • Journal: African Journal of Marine Science
    White stumpnose Rhabdosargus globiceps is the main target of the linefishery in Saldanha Bay. Increased fishing pressure over the last three decades, particularly by the recreational sector, has led to concerns regarding sustainability of the local white stumpnose stock. The...
  2. Influence of buoyancy and vertical distribution of sardine <em>Sardinops sagax</em> eggs and larvae on their transport in the northern Benguela ecosystem

    Influence of buoyancy and vertical distribution of sardine <em>Sardinops sagax</em> eggs and larvae on their transport in the northern Benguela ecosystem

    Item type: Journal Article • Journal: South African Journal of Marine Science
    In recent years, sardine Sardinops sagax spawning has been recorded inshore off central Namibia. Field observations on eggs and laboratory measurements show that spawning, demonstrated by the distribution of newly spawned eggs, takes place just below the upper mixed layer...
  3. INFLUENCE OF THE CLAY TYPES ILLITE AND MONTMORILLONITE ON THE UPTAKE OF<sup>65</sup> Zn BY <em>SCENEDESMUS OBLIQUUS.</em>

    INFLUENCE OF THE CLAY TYPES ILLITE AND MONTMORILLONITE ON THE UPTAKE OF<sup>65</sup> Zn BY <em>SCENEDESMUS OBLIQUUS.</em>

    Item type: Journal Article • Journal: Journal of the Limnological Society of Southern Africa
    The stimulatory effect of the clays illite and montmorillonite on zinc uptake by Scenedesmus obliquus is discussed. The competitive effects of hydrogen, phosphate, magnesium and copper ions on zinc uptake are illustrated. This competition is reduced in the presence of...
  4. HYDROCHEMISTRY OF THE UPPER ORANGE RIVER CATCHMENT

    HYDROCHEMISTRY OF THE UPPER ORANGE RIVER CATCHMENT

    Item type: Journal Article • Journal: Journal of the Limnological Society of Southern Africa
    A four year pre-impoundment study of the catchment of the Hendrik Verwoerd Dam was conducted. The Orange River was the major source of dissolved chemicals and suspended sediments, while the Caledon River contributed 24 and 30% respectively, and the Kraai...
  5. STERILIZATION OF SUSPENDED SEDIMENTS BY GAMMA RADIATION

    STERILIZATION OF SUSPENDED SEDIMENTS BY GAMMA RADIATION

    Item type: Journal Article • Journal: Journal of the Limnological Society of Southern Africa
    Gamma radiation as an alternative sterilization technique for silt and clay suspensions is evaluated. It is compared to autoclaving in regard to sterility and changes in physical and chemical properties of the suspensions. A minimum radiation dose rate of 5...
  6. SOME PROPERTIES OF SUSPENDED SEDIMENT ADSORBED CATIONS IN TURBID FRESHWATERS OF SOUTH AFRICA

    SOME PROPERTIES OF SUSPENDED SEDIMENT ADSORBED CATIONS IN TURBID FRESHWATERS OF SOUTH AFRICA

    Item type: Journal Article • Journal: Journal of the Limnological Society of Southern Africa
    Large quantities of suspended sediments are common in many of South Africa's fresh-waters. Temporal and spatial variations in tile amounts of cations adsorbed were recorded. The adsorption appears to be dependent on valency, because greater quantities of the higher valencies...
  7. LEAF AREA AS A MEASURE OF STANDING CROP OF FLOATING AQUATIC MACROPHYTES

    LEAF AREA AS A MEASURE OF STANDING CROP OF FLOATING AQUATIC MACROPHYTES

    Item type: Journal Article • Journal: Journal of the Limnological Society of Southern Africa
    Leaf area is evaluated as a measure of standing crop of Salvinia molesta Mitchell and Azolla filiculoides Lam. cultures under controlled conditions. Growth rates as derived from leaf area determinations agreed with pigment extractions and fresh and dry weight measures...
  8. Spawning strategies and transport of early stages of the two Cape hake species, <em>Merluccius paradoxus</em> and <em>M. capensis</em>, in the southern Benguela upwelling system

    Spawning strategies and transport of early stages of the two Cape hake species, <em>Merluccius paradoxus</em> and <em>M. capensis</em>, in the southern Benguela upwelling system

    Item type: Journal Article • Journal: African Journal of Marine Science
    Seasonal and short-term variability of environmental parameters influence the spawning strategies of fish species. In this study, the spawning strategies and the transport of early stages of the two Cape hake species off South Africa were investigated. Distribution of eggs...
  9. Diel vertical migration of anchovy <em>Engraulis encrasicolus</em> larvae in the northern Benguela

    Diel vertical migration of anchovy <em>Engraulis encrasicolus</em> larvae in the northern Benguela

    Item type: Journal Article • Journal: African Journal of Marine Science
    The diel vertical migration of anchovy Engraulis encrasicolus larvae was studied in the northern Benguela during a survey in April 2001. The diel pattern is described in relation to the degree of swimbladder inflation and the vertical structure of temperature...