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Towards a catchability constant for trawl surveys of Namibian hake
Item type: Journal Article • Journal: South African Journal of Marine Science • Authors: I. Huse T. Iilende T. StrømmeA trawl catches only a portion of the fish in its path. The term catchability therefore refers to the fraction of the available fish caught. A method was developed and tested to establish catchability constants for trawl surveys of Namibian... -
Depth-stratified density estimates and distribution of the Cape hake Merluccius capensis and M. paradoxus off Namibia deduced from survey data, 1990–1999
Item type: Journal Article • Journal: South African Journal of Marine Science • Authors: L-M. BurmeisterIn 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... -
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 • Authors: D. S. Butterworth H. F. GeromontDuring 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... -
A decade of exploitation and management of the Namibian hake stocks
Item type: Journal Article • Journal: South African Journal of Marine Science • Authors: A. van der WesthuizenThe hake resource is the most important commercial fish species in the demersal sector of Namibia's fisheries, both in terms of annual catch and contribution to Gross Domestic Product (GDP). The fishery now spans four decades. In the 1960s and... -
Dynamics of the pelagic component of Namibian hake stocks
Item type: Journal Article • Journal: South African Journal of Marine Science • Authors: T. Iilende T. Strømme E. JohnsenA study was undertaken to investigate the spatial, diurnal and interannual dynamics of the pelagic component of Namibian hake stocks. Data were derived from trawl surveys conducted on board the R.V. Dr Fridtjof Nansen during the period 1991–1999. In addition... -
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 • Authors: J. P. Glazer D. S. ButterworthCatch 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... -
Spatial description of hake-directed fishing activity off the west coast of South Africa
Item type: Journal Article • Journal: African Journal of Marine Science • Authors: TP Fairweather AJ Booth WHH Sauer RW LeslieHistorically, the two species of Cape hakes Merluccius capensis and M. paradoxus off South Africa were commercially exploited exclusively by demersal trawling. In 1994, hake-directed demersal longline was introduced on an experimental basis, and in 1998 was initiated as a... -
Escapement of Cape hakes under the fishing line of the Namibian demersal sampling trawl
Item type: Journal Article • Journal: African Journal of Marine Science • Authors: T Jørgensen A Engås E Johnsen T Iilende P Kainge P SchneiderSwept area surveys in Namibian waters provide input data to the stock assessment model. To evaluate the model's predictions, it is important to understand the catch efficiency of sampling trawls. The objective of this study was to establish whether Cape... -
Merluccius capensis spawn in Namibian waters, but do M. paradoxus?
Item type: Journal Article • Journal: African Journal of Marine Science • Authors: P Kainge OS Kjesbu A Thorsen AG SalvanesSpawning time and areas, and the length of the spawning season of shallow-water (Merluccius capensis) and deep-water (M. paradoxus) hake, were investigated from bottom trawl collections taken in Namibian waters between September 1998 and October 2000 and from August to... -
Assessment of the South African hake resource taking its two-species nature into account
Item type: Journal Article • Journal: African Journal of Marine Science • Authors: RA Rademeyer DS Butterworth ÉE PlagányiThe commercially valuable hake fishery off South Africa consists of two morphologically similar species, the shallow-water Cape hake Merluccius capensis and the deep-water Cape hake M. paradoxus. Because catch-and-effort statistics collected from the fishery are not species-disaggregated, previous published quantitative... -
A history of recent bases for management and the development of a species-combined Operational Management Procedure for the South African hake resource
Item type: Journal Article • Journal: African Journal of Marine Science • Authors: RA Rademeyer DS Butterworth ÉE PlagányiThe bases for historical catch limits placed on the hake fishery are reviewed in brief for earlier years and then in some depth over the period from 1991 when the Operational Management Procedure (OMP) approach was introduced for this fishery... -
A review of the assessments of the major fisheries resources in South Africa
Item type: Journal Article • Journal: African Journal of Marine Science • Authors: CL de Moor --- Marine Resource Assessment and Management Group (MARAM), Department of Mathematics and Applied Mathematics, South Africa SJ Johnston --- Marine Resource Assessment and Management Group (MARAM), Department of Mathematics and Applied Mathematics, South Africa A Brandão --- Marine Resource Assessment and Management Group (MARAM), Department of Mathematics and Applied Mathematics, South Africa RA Rademeyer --- Marine Resource Assessment and Management Group (MARAM), Department of Mathematics and Applied Mathematics, South Africa JP Glazer --- Branch: Fisheries Management, Department of Agriculture, South Africa LB Furman --- Marine Resource Assessment and Management Group (MARAM), Department of Mathematics and Applied Mathematics, South Africa DS Butterworth --- Marine Resource Assessment and Management Group (MARAM), Department of Mathematics and Applied Mathematics, South AfricaThe waters off South Africa's coastline boast a rich mix of commercially fished species. Quantitative assessments of these marine resources have developed from simple methods first applied in the 1970s, to models that encompass a wide range of methodologies. The... -
Characterisation of the dietary relationships of two sympatric hake species, Merluccius capensis and M. paradoxus, in the northern Benguela region using fatty acid profiles
Item type: Journal Article • Journal: African Journal of Marine Science • Authors: JA Iitembu --- Department of Fisheries and Aquatic Sciences, Namibia NB Richoux --- Department of Zoology and Entomology, South AfricaThe two sympatric species of Cape hake, Merluccius capensis and M. paradoxus, have been the main targets of bottom-trawl fisheries off Namibia for several decades. The feeding ecology of these hakes has been studied mainly using stomach content analyses and... -
Population abundance and seasonal migration patterns indicated by commercial catch-per-unit-effort of hakes (Merluccius capensis and
M. paradoxus ) in the northern Benguela Current Large Marine Ecosystem Item type: Journal Article • Journal: African Journal of Marine Science • Authors: JN Kathena --- National Marine Information and Research Centre (NatMIRC), Ministry of Fisheries and Marine Resources, Namibia D Yemane --- Branch: Fisheries Management, Department of Agriculture, Forestry and Fisheries (DAFF), South Africa N Bahamon --- Centre d’Estudis Avançats de Blanes (CEAB – CSIC), Spain T Jansen --- National Institute of Aquatic Resources (DTU Aqua), DenmarkWe developed generalised additive models (GAMs) to estimate standardised time-series of population abundance indices for assessment purposes and to infer ecological and behavioural information on northern Benguela hakes, Merluccius capensis and M. paradoxus, using haul-by-haul commercial trawl catch-rate data as... -
Incidence of gummosis disease in silky hakea under natural conditions in South Africa
Item type: Journal Article • Journal: South African Journal of Plant and Soil • Authors: Alan R Wood --- , South Africa Alana Den Breeyen --- , South AfricaThe pathogen Colletotrichum acutatum J.H.Simmonds was developed in South Africa during the 1980s as a mycoherbicide to control invasive silky hakea (Hakea sericea Schrad. & J.C.Wendl.) and was subsequently widely used by a variety of land managers to induce gummosis... -
Geographical and seasonal patterns in the diet of Cape fur seals Arctocephalus pusillus pusillus in Namibia, based on extensive scat analyses
Item type: Journal Article • Journal: African Journal of Marine Science • Authors: DN Mwaala --- University of Namibia, Namibia MR Wilhelm --- University of Namibia, Namibia SP Kirkman --- Fisheries and the Environment (DFFE): Branch Oceans and Coasts, South Africa J-P Roux --- Ministry of Fisheries and Marine Resources, NamibiaNamibia's population of Cape fur seals Arctocephalus pusillus pusillus is a major constituent of top predator biomass in the northern Benguela upwelling system. Understanding their diet is key to comprehending their role in the ecosystem and potential drivers of recent...