A new species of electric ray of the genus Narcine Henle, 1834 from the South-Western Indian Ocean (Chondrichthyes: Torpediniformes: Narcinidae)

The Namibian linefishery is a multisector fishery, with recreational and commercial sectors targeting overlapping species. Prior to 1990, catch data were recorded for the boat sector, but little research was done on the population dynamics of any of the species. Hence, none of the stocks were assessed owing to the lack of parameter estimates for fisheries modelling. Current management regulations for the Namibian linefishery are therefore not based on scientific investigations but, for historical reasons, were adapted from South African legislation for similar species. From 1994, linefish research in Namibia focused on the life history and population dynamics of silver kob Argyrosomus inodorus and West Coast steenbras Lithognathus aureti, important species in both commercial and recreational sectors. A roving-roving creel survey was used to determine effort and catches of recreational shore-anglers. Both species were assessed using yield-per-recruit models. Based on the results, reduced daily bag limits and the implementation of size limits for the recreational sector were proposed. For the commercial sector, the introduction of a total allowable catch would seem to be the best option. Results from an economic survey indicated that the recreational sector earns six times more for the country annually than the commercial sector.     

A cryptic species of Mytilus (Mollusca: Bivalvia) on the west coast of South Africa

A biochemical genetic study of the mussels Perna perna and Choromytilus meridionalis on the west coast of South Africa revealed the presence of an unreported mytilid mussel that had previously been mistaken, because of its shell colour polymorphism, for either P. perna or a hybrid between P. perna and C. meridionalis. The gene products of 19 protein-coding loci in P. perna. C. meridionalis and in the newly recognized mussel were examined by means of horizontal starch-gel electrophoresis. The results showed that there was no allele-frequency overlap between any of these mussel taxa, thus implying little or no genetic relatedness between them. A morphological examination showed that the previously unreported mytilid has a pitted resilial ridge (similar to that of Perna), an anterior adductor muscle (unlike either Perna or Choromytilus), and an undivided posterior foot retractor-muscle scar (unlike Perna). Such features are diagnostic of the genus Mytilus. The South African Mytilus has morphological traits that are more characteristic of M. galloprovincialis of the Mediterranean Sea than of the more cosmopolitan M. edulis. which occurs in the northern and southern Pacific and Atlantic oceans. A large heterozygosity in Mytilus sp. argues against a recent dispersal from the Mediterranean Sea via a small founder population. Rather, the presence of Mytilus sp. in South Africa may represent a relict population of a wider geographic distribution of M. galloprovincialis resulting from Pleistocene cooling. However, the warmer water at lower latitudes could have still prevented dispersal of M. edulis, a species adapted to colder waters.     

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.     

Annual and interannual variability in the South-East Atlantic during the 20th century

Long time-series of sea surface temperature (SST) and pseudo wind stress (τ) in six areas in the South-East Atlantic are analysed as possible inputs into fisheries models. The areas encompass oceanic and coastal regimes. A clear seasonal signal is evident in all areas, with an amplitude in SST of 3–4°C in the upwelling areas and 5°C farther offshore and on the Agulhas Bank. Warming lags in the north and offshore by 1–2 months. Monthly variability is highest in the upwelling areas. An increasing trend in SST is suggested in all areas, the post-World War II era being about 1,0°C warmer than earlier periods. Some coherence occurs between areas at times, although at other times the anomalies are distinctly out of phase. There is a suggestion of an upward trend in the equatorward wind stress in some offshore areas after 1964, with a sharp change in 1975. Benguela Niños are evident in the environmental record and have a periodicity of around 10 years.     

The 26 December 2004 Sumatra tsunami recorded on the coast of West Africa

Analysis of sea-level data obtained from the Atlantic Global Sea Level Observing System (GLOSS) sea-level station at Takoradi, Ghana, West Africa, clearly reveals a tsunami signal associated with the M_w = 9.3 Sumatra earthquake of 26 December 2004 in the Indian Ocean. The tsunami arrived at this location on 27 December 2004 at approximately 01:38 UTC (which is close to the expected tsunami arrival time at that site), after travelling for more than 24 hours. The first wave was negative (trough), in contrast with the South African stations where the first wave was mainly positive (crest). The dominant observed period at Takoradi was about 42 minutes. The maximum trough-to-crest wave height (41cm) was observed on 28 December at 00:15 UTC. There were two distinct tsunami 'bursts', separated in time by about 14 hours, the larger being the second burst. A small residual lowering of the sea level (～15cm) during the tsunami and for several days afterwards, and a delayed (～4.5 days) lowering of seawater temperature (up to ～4.5°C), was observed, possibly indicating the presence of internal waves through the Gulf of Guinea associated with propagating tsunami waves. The prominent tsunami signal found in the Takoradi record suggests that tsunami waves could also be found at other sites off the West African coast.     

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.     

Atlas Mapping in the 21st Century

Atlases are changing. The paper paradigm of maps and atlases has pervaded recent cartographic history. By nature that paradigm serves, as well as defines, a specific audience in terms of use and presentation. In the lab and at the printing press, the paper paradigm demands certain design and production flows that will drastically change through evolutions in data structures, mapmaking techniques, and presentation methods. Technological transformations in mapping influence much of this change. The implications for the creation and distribution of atlases are significant. With that in mind, this paper addresses a number of issues that relate to the technological evolution of atlases from paper to digital products: the distinction between paper and digital products and services and the implications of that distinction for atlas design—particularly for web-based services; facilitating data and its application to the evolution of map/atlas products; and a redefinition of "atlas" and the "audience" for an atlas.