Articles by Author: D S Butterworth

Search results for D S Butterworth

We found 31 results for you
  1. 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...
  2. GLM-based standardization of the catch per unit effort series for South African west coast hake, focusing on adjustments for targeting other species

    GLM-based standardization of the catch per unit effort series for South African west coast hake, focusing on adjustments for targeting other species

    Item type: Journal Article • Journal: South African Journal of Marine Science
    Catch per unit effort (cpue) data for the South African west coast Cape hakes Merluccius capensis and M. paradoxus were standardized by applying the Generalized Linear Modelling (GLM) technique. The resulting standardized series indicated that resource abundance declined at a...
  3. Is <em>f</em>
               <sub>0.1</sub> an appropriate harvesting strategy for the Cape hakes?

    Is <em>f</em> <sub>0.1</sub> an appropriate harvesting strategy for the Cape hakes?

    Item type: Journal Article • Journal: South African Journal of Marine Science
    Time-series of catch per unit effort (CPUE) for the Cape hake stocks demarcated by ICSEAF in the Benguela region show steady declines until the late 1970s, followed by slowly increasing trends once catch levels were reduced. Analysis of these data...
  4. Towards rational harvesting of the South African anchovy considering survey imprecision and recruitment variability

    Towards rational harvesting of the South African anchovy considering survey imprecision and recruitment variability

    Item type: Journal Article • Journal: South African Journal of Marine Science
    Alternative harvesting schemes for the South African anchovy resource are considered. For this preliminary study, strategies in which quotas are simply related to the pre-catch survey estimates of spawning biomass and recruitment are investigated, using a Monte Carlo simulation approach...
  5. Population estimates for bottlenose dolphins <em>Tursiops truncatus</em> in Natal and Transkei waters

    Population estimates for bottlenose dolphins <em>Tursiops truncatus</em> in Natal and Transkei waters

    Item type: Journal Article • Journal: South African Journal of Marine Science
    Population estimates of bottlenose dolphins Tursiops truncatus on the Natal (five replicates) and Transkei (two replicates) coasts are made from aerial inshore strip-transects conducted between 23 April and 5 May 1985. Counts of dolphin schools and numbers were made in...
  6. VPA with <em>ad hoc</em> tuning: implementation for disaggregated fleet data, variance estimation, and application to the Namibian stock of Cape horse mackerel <em>Trachurus trachurus capensis</em>

    VPA with <em>ad hoc</em> tuning: implementation for disaggregated fleet data, variance estimation, and application to the Namibian stock of Cape horse mackerel <em>Trachurus trachurus capensis</em>

    Item type: Journal Article • Journal: South African Journal of Marine Science
    The arbitrariness of Virtual Population Analysis (VPA) solutions in the absence of objectively based procedures to tune both oldest-age and most-recent-year terminal fishing mortalities is demonstrated. The formalism for tuning the latter set of mortalities with effort data from one...
  7. On an approach for comparing the implications of alternative fish stock assessments, with application to the stock of Cape hake <em>Merluccius</em> spp. off northern Namibia

    On an approach for comparing the implications of alternative fish stock assessments, with application to the stock of Cape hake <em>Merluccius</em> spp. off northern Namibia

    Item type: Journal Article • Journal: South African Journal of Marine Science
    The 1989 meeting of an ad hoc Working Group on Stock Assessment Methodology at the International Commission for the Southeast Atlantic Fisheries (ICSEAF) suggested a "risk analysis" approach to contrast the implications of the different estimates of Total Allowable Catch...
  8. Assessment and management of South African marine resources during the period of the Benguela Ecology Programme: key lessons and future directions

    Assessment and management of South African marine resources during the period of the Benguela Ecology Programme: key lessons and future directions

    Item type: Journal Article • Journal: South African Journal of Marine Science
    Three important developments in resource assessment and management during the period of the Benguela Ecology Programme are discussed. The first is the recognition of the limited information content for assessment purposes of the available data for many of the Benguela's...
  9. The effects of errors in the placement of the boundary between the West and South Coast hake <em>Merluccius</em> spp. stocks on the performance of the current hake management procedure

    The effects of errors in the placement of the boundary between the West and South Coast hake <em>Merluccius</em> spp. stocks on the performance of the current hake management procedure

    Item type: Journal Article • Journal: South African Journal of Marine Science
    The present basis for management recommendations for the Cape hake resource off South Africa assumes that there are two ("West Coast" and "South Coast") stocks, separated by a boundary line running south-west from Cape Agulhas, even though survey results suggest...
  10. Stock assessment and risk analysis for the South Atlantic population of albacore <em>Thunnus alalunga</em> using an age-structured production model

    Stock assessment and risk analysis for the South Atlantic population of albacore <em>Thunnus alalunga</em> using an age-structured production model

    Item type: Journal Article • Journal: South African Journal of Marine Science
    The South Atlantic population of albacore is assessed by means of an (observation-error) age-structured production model. Relative abundance (cpue) series up to 1993 from the Republic of China, Japan and South Africa are used in the model-fitting process. Coefficients of...