Articles by Keyword: Abundance Trends

Search results for Abundance Trends

We found 106 results for you
  1. Spatial considerations when monitoring reef fishes

    Spatial considerations when monitoring reef fishes

    Item type: Journal Article • Journal: African Journal of Marine Science
    Spatial dependence can obscure relationships between response and explanatory variables because of structuring within the residuals reducing variance and biasing coefficient estimates. Here, we highlight the influence of the spatial component, in the presence of spatial dependence, on abundance trends...
  2. Access Development in South African Mountainous Plantations—Problems, Trends, Research

    Item type: Journal Article • Journal: South African Forestry Journal
    The forest road network in South Africa's plantations was rapidly developed to provide access for planting, fire protection and later logging. The result today is a fairly high road density of rather low standard roads!
  3. The influence of rainfall on the seasonal abundance and flight activity of the maize stalk borer, <em>Busseola fusca</em> in South Africa

    The influence of rainfall on the seasonal abundance and flight activity of the maize stalk borer, <em>Busseola fusca</em> in South Africa

    Item type: Journal Article • Journal: South African Journal of Plant and Soil
    This study attempts to demonstrate the extent to which seasonal fluctuations in the number of Busseola fusca (Fuller) moths can be explained by precipitation data. Daily flight activity is shown to be enhanced by cool, humid conditions and restricted by...
  4. Grain yield and contribution of symbiotically fixed nitrogen to seed in cowpea varieties using the <sup>15</sup>N natural abundance technique

    Grain yield and contribution of symbiotically fixed nitrogen to seed in cowpea varieties using the <sup>15</sup>N natural abundance technique

    Item type: Journal Article • Journal: South African Journal of Plant and Soil
    Identification of cowpea varieties with superior grain yield and high nitrogen fixing potential is crucial to increasing productivity of the crop among small-scale farmers in the Northern Province. A field experiment was established during the 1997/98 growing season to evaluate...
  5. Recent population trends of African penguins <em>Spheniscus demersus</em> in Namibia

    Recent population trends of African penguins <em>Spheniscus demersus</em> in Namibia

    Item type: Journal Article • Journal: South African Journal of Marine Science
    The African penguin Spheniscus demersus is endemic to southern Africa and is listed overall as "vulnerable". Over the past century, however, the Namibian population has been severely reduced and is currently listed as "critically endangered". Recent trends at Possession, Halifax,...
  6. Depth-stratified density estimates and distribution of the Cape hake <em>Merluccius capensis</em> and <em>M. paradoxus</em> off Namibia deduced from survey data, 1990–1999

    Depth-stratified density estimates and distribution of the Cape hake <em>Merluccius capensis</em> and <em>M. paradoxus</em> off Namibia deduced from survey data, 1990–1999

    Item type: Journal Article • Journal: South African Journal of Marine Science
    In this study demersal survey data for the period 1990–1999 are used to investigate the average distribution of the Cape hake Merluccius capensis and M. paradoxus off Namibia in terms of density and mean length. Further, biomass estimates are compared...
  7. Variable spatial structure of schooling pelagic fish off Namibia: implications for acoustic surveys

    Variable spatial structure of schooling pelagic fish off Namibia: implications for acoustic surveys

    Item type: Journal Article • Journal: South African Journal of Marine Science
    Schools of horse mackerel Trachurus trachurus capensis, sardine Sardinops sagax and round herring Etrumeus whiteheadi were surveyed by conventional echo-integration along systematic transects. The transects were surveyed twice, in opposite directions. Clupeoid biomass was concentrated in a few dense aggregations,...
  8. Evaluation of a class of possible simple interim management procedures for the Namibian hake fishery

    Evaluation of a class of possible simple interim management procedures for the Namibian hake fishery

    Item type: Journal Article • Journal: South African Journal of Marine Science
    During 1997, considerable scientific differences arose about the status of the Namibian hake (Merluccius capensis and M. paradoxus) resource, and as to whether the hake Total Allowable Catch (TAC) should be substantially decreased or increased. These differences revolved primarily around...
  9. Fishery characteristics and abundance estimates of the mangrove crab <em>Scylla serrata</em> in southern Tanzania and northern Moçambique

    Fishery characteristics and abundance estimates of the mangrove crab <em>Scylla serrata</em> in southern Tanzania and northern Moçambique

    Item type: Journal Article • Journal: South African Journal of Marine Science
    The mud crab Scylla serrata is lightly exploited along the East African seaboard. This study reports on fishing practices and gives preliminary estimates of abundance and size structures of the mud crab populations in Utende, Chole Island and Juani Island,...
  10. ON THE RELATIONSHIP BETWEEN TIGERFISH AND SARDINES IN LAKE KARIBA

    ON THE RELATIONSHIP BETWEEN TIGERFISH AND SARDINES IN LAKE KARIBA

    Item type: Journal Article • Journal: Journal of the Limnological Society of Southern Africa
    There was a clear relationship in Lake Kariba between the abundance of young-of-the-year (0+) tigerfish and the sardines on which they prey. The abundant sardine population that existed before commercial fishing began accounted for the increase in tiger-fish which occurred...