南方CASS和MAPGIS精确编制剖面图的方法

本文探索出南方CASS和MAPGIS软件如何直接利用勘探线测量坐标成果数据,精确编制数字化剖面图,重点介绍勘探线、探矿工程点、坐标网格线投影平面图,以及剖面地形起伏线、剖面高程标注、剖面图上地层界线、矿层及探矿工程的精确编制方法。对图切剖面也提出了编制思路和图切坐标数据的获取方法。编制方法成图精度高、快捷,在实际工作中有很高的实用价值。     

Discrepancy between otolith and tag-recovery estimates of growth for two South African surf-zone teleost species

Growth rates determined from recovered tagged galjoen Dichistius capensis and white steenbras Lithognathus lithognathus were compared to predictions from growth models based on otolith ring counts. Galjoen could not be sexed externally, but it was assumed that all fish >450 mm total length were females, which grow faster than males. Those smaller than this were assumed to include mostly males and were treated as a "male" sample. Male and female white steenbras grow equivalently. Tagged "male" (n = 322), and female galjoen (n = 34) and white steenbras (n = 14) grew more slowly than the model predictions. The discrepancy is likely attributable to the physiological effect of external tags on growth.     

Seasonal variation of oxygen deficiency in waters off southern South West Africa in 1975 and 1976 and its relation to the catchability and distribution of the Cape rock lobster Jasus lalandii

The major processes involved in the supply and removal of dissolved oxygen in the shelf region between 24 and 28°S are discussed in relation to the development of oxygen-deficient conditions. The area subject to this oxygen deficiency varies both seasonally and geographically. It is suggested that both the shallow distribution of rock lobster in this part of the Benguela Current system and the periodically low catch per unit effort may be related to the onset of oxygen deficiency. Preliminary laboratory findings indicate that avoidance of oxygen-deficient areas by rock lobster might not be caused solely by the lack of oxygen per se, but by the co-existence at low oxygen concentrations of toxic reduced compounds such as hydrogen sulphide.     

First records of the longnose spiny dogfish Squalus blainvillei (Squalidae) and the deep-water stingray Plesiobatis daviesi (Urolophidae) from South African waters

Deep-set longline investigations of the slope waters off northern KwaZulu-Natal on the east coast of South Africa confirmed the first records of the longnose spiny dogfish Squalus blainvillei (Squalidae) and the deep-water stingray Plesiobatis daviesi (Urolophidae) from South African waters.     

A knowledge base for management of the capital-intensive fishery for small pelagic fish off South Africa

As a contribution to South Africa's move towards an ecosystem approach to fisheries management, this study explores the existence of common perceptions about South Africa's pelagic fishery between resource users and scientists. It represents a collaborative research effort of social and natural scientists. A brief overview is given of the southern Benguela upwelling ecosystem and small pelagic fish resources, the fishery, and management of the fishery. Stakeholder knowledge and views were determined by conducting open-ended qualitative local knowledge interviews. Candidate indicators to address five major issues raised in the interviews were selected: length-at-50% maturity, total mortality, exploitation rate, proportion of bycatch, mean length of catch, and centre of gravity of catches. The indicator approach is shown to be a useful tool to manage the South African small pelagic fishery, and can be made compatible with existing management approaches. The foundation of a good adaptive fisheries management system is a data collection system that enables multi-disciplinary analysis and provides a basis on which decisions can be made.     

Achievements and lessons learned from the Benguela Environment,Fisheries, Interaction and Training (BENEFIT) research programme

This paper considers the scientific achievements of the Benguela Environment, Fisheries, Interaction and Training (BENEFIT) Programme as reflected in 29 internally evaluated BENEFIT research projects carried out between 1998 and 2007 when the programme ended, and draws a number of important lessons relevant to future regional marine research programmes in the Benguela from the manner in which the projects were initiated and executed. The founding of BENEFIT, its organisational structures, and the way in which the projects were planned, formulated and executed through these structures are outlined. The major findings and other achievements of the research on fish resources, the environment and the linkages between them are discussed under these headings, and in the case of projects on resources, in relation to key questions developed from guidelines in the BENEFIT Science Plan. Based largely on a final evaluation by the programme's International Scientific Advisory Panel, it is concluded that BENEFIT added materially to greater knowledge of the dynamics of key resources in the Benguela, markedly increased the extent of environmental monitoring in the region, and the capacity for future such monitoring, and added significant new insights into key physical, chemical and biological processes of relevance to stock dynamics. BENEFIT's most important achievement in a wider sense was the pioneering development, almost from scratch, of a regional marine research community which, inter alia, was crucial in the development of other regional marine research activities in the Benguela, such as the Benguela Current Large Marine Ecosystem (BCLME) Programme whose primary objective was the creation of a Benguela Current Commission. In this sense, the establishment of the Commission in 2007 to deal with transboundary management of the living resources of the Benguela Current and regional biodiversity issues can be regarded as the greatest single legacy of BENEFIT.     

Towards adaptive approaches to management of the South African Abalone Haliotis Midae Fishery

The South African abalone Haliotis midae resource is widely perceived as being under threat of over-exploitation as a result of increased poaching. In this paper, reservations are expressed about using catch per unit effort as the sole index of abundance when assessing this fishery, particularly because of the highly aggregatory behaviour of the species. A fishery-independent survey has been initiated and is designed to provide relative indices of abundance with CVs of about 25% in most of the zones for which Total Allowable Catchs (TACs) are set annually for this fishery. However, it will take several years before this relative index matures to a time-series long enough to provide a usable basis for management. Through a series of simple simulation models, it is shown that calibration of the survey to provide values of biomass in absolute terms would greatly enhance the value of the dataset. The models show that, if sufficient precision (CV 50% or less) could bc achieved in such a calibration exercise, the potential for management benefit is improved substantially, even when using a relatively simple management procedure to set TACs. This improvement results from an enhanced ability to detect resource declines or increases at an early stage, as well as from decreasing the time period until the survey index becomes useful. Furthermore, the paper demonstrates that basic modelling techniques could usefully indicate which forms of adaptive management experiments would improve ability to manage the resource, mainly through estimation of the level of precision that would be required from those experiments. The results of this study are particularly applicable to fishing zones for which there are insufficient other data to perform a standard stock assessment.     

Determination of moult stage in the South African West Coast rock lobster Jasus lalandii (h. Milne Edwards) (Crustacea: Decapoda)

Nine stages and substages of post-, inter- and premoult were distinguished in the West Coast rock lobster Jasus lalandii by microscopic examination of the cuticle, epidermal retraction and setal development in the pleopods. The postmoult condition is characterized by progressive thickening of the setal walls and cuticle through to inter-moult. Premoult commences with apolysis (Stage D₀), followed by setal development (Stage D₁', D₁", D₁'") and culminates with cuticle deposition (Stage D₂), The diagnostic features of the stages are generally similar to those of other decapod crustaceans.     

A note on the diet of Cape cormorant Phalacrocorax capensis at Mercury Island,South West Africa,in November 1978

During November 1978, Cape cormorants Phalacrocorax capensis at Mercury Island, off South West Africa (Namibia), consumed practically exclusively pelagic gobies Sufflogobius bibarbalus. The mean number of fish per regurgitation was 52 with a mean caudal length of 48 mm and an estimated mean mass of 1.7 g. The estimated mean original mass of stomach contents was 75 g. These Cape cormorants took significantly smaller pelagic gobies than did bank cormorants P. neglectus sampled concurrently at the same locality.