Showing papers in "Transactions of The Royal Society of South Africa in 1986"
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TL;DR: Sloven as discussed by the authors states that science is a search for the truth, the truth being "a pragmatic concept which explains phenomena." Science, he continues, depends on certain pre-suppositions, including a belief in order and harmony, although science itself is never static but constantly undergoing change as well as expansion.
Abstract: A. W. Sloan (1979), in his elegant presidential address to the Royal Society of South Africa, states that science is "a search for the truth," the truth being "a pragmatic concept which explains phenomena." Science, he continues, depends on certain pre-suppositions, including a belief in order and harmony, although science itself is never static but constantly undergoing change as well as expansion. The scientist, observes Sloan, starts with some preconceived theory, and selects the relevant (as opposed to random) data - in order not to waste time. He makes a point of including Hume's (1777) contention that all science is contingent. Sloan also refers to Thomas Kuhn (1962) and Karl Popper (1959, 1972) in his address; and, perhaps surprisingly, some degree of formal logical congruency is discernible, despite their differing approaches to the subject, among the three of them in their scientific thinking.
44 citations
TL;DR: Shrimp size-frequency distributions displayed a pattern of bimodality in summer/autumn from November to March, becoming polymodal during the year.
Abstract: SUMMARY The shrimp Palaemon pacificus was sampled in Zostera capensis beds in three eastern Cape estuaries (Sundays, Swartkops and Kromme) In all three estuaries shrimp numbers and biomass in the Zostera generally exhibited seasonal fluctuations, with summer/autumn peaks from November to March (density 200–400 m−2; dry mass 3–6 g m−2) declining to winter/spring minima from June to September (20–100 m−2; 0,3-1,5 g m−2) The Kromme had the highest mean annual shrimp biomass (dry mass 2,86-3,10 g m−2), followed by the Sundays (2,69 g m−2) and the Swartkops (2,11-2,22 g m−2) Shrimp size-frequency distributions displayed a pattern of bimodality in summer/autumn from November to March, becoming polymodal during the year A temporal variation of sex ratio was evident with overall M:F ratios of 1:2,27 in the Sundays and 1:1,96 and 1:1,82 at two Swartkops stations A mean of 4 cohorts per annum was resolved for the Sundays and 3,1 for the Swartkops, with mean residence times in the Zostera of 11,9 months and 10
23 citations
TL;DR: The present taxonomic status of the genus Haliotis in South Africa is discussed and problems of classification are described and distribution maps, maximum sizes and morphological features presented.
Abstract: SUMMARY The present taxonomic status of the genus Haliotis in South Africa is discussed. Problems of classification are described and distribution maps, maximum sizes and morphological features presented.
18 citations
TL;DR: Rumen and vegetation analyses were employed to investigate the diets of springbok and Merino sheep on Karoo vegetation during a period of low rainfall, finding that Springbok showed a preference for certain plant species which are considered unpalatable to Merino Sheep.
Abstract: SUMMARY Rumen and vegetation analyses were employed to investigate the diets of springbok (Antidorcas marsupialis) and Merino sheep (Ovis aries) on Karoo vegetation during a period of low rainfall. Supplementary feeds (maize) were utilised by Merino sheep, not by springbok. Karoo shrubs predominated in the veld and were preferred by springbok, but not by Merino sheep. Grasses, in a state of lignification, were preferred by Merino sheep but not by springbok. A choice of some ‘less palatable’ shrubs (esp. Pentzia spp.) was apparent in the diet of springbok; palatable shrubs and geophytes were also preferred while most unpalatable shrubs were not. Springbok showed a preference for certain plant species which are considered unpalatable to Merino sheep. Variation between the diets of springbok rams and ewes is believed to be related to social structure. Findings on diet tally with the activity patterns, habitat selection and vegetation impact of the two species. A combination of springbok and Merino sheep shou...
18 citations
TL;DR: The daily activity patterns of springbok and Merino sheep were studied under open-range conditions in the Karoo for 80 days spanning one whole year, during a period of drought, to determine whether these patterns were affected by drought or by their greater dietary selectivity.
Abstract: SUMMARY The daily activity patterns of springbok and Merino sheep were studied under open-range conditions in the Karoo for 80 days spanning one whole year, during a period of drought. Springbok spent a greater amount of time foraging (in more frequent bouts) than Merino sheep perhaps as a consequence of their greater dietary selectivity. Springbok had more time available for resting behaviour during optimal conditions for plant growth. As the pasture deteriorated, springbok devoted more time to foraging while diurnal behaviour rhythms disappeared. Major springbok mortality occurred when resting behaviour was restricted to one hour per day. Supplementary feed was supplied and utilised solely by Merino sheep which subsequently devoted more time to resting behaviour. Merino sheep spent less time foraging on hot days.
15 citations
TL;DR: Observed inter-specific differences suggest that a combination of springbok and Merino sheep in a 350 ha paddock on a game ranch in the Karoo would lead to a better utilisation of the vegetation.
Abstract: SUMMARY The distributions of springbok and Merino sheep in a 350 ha paddock on a game ranch in the Karoo were monitored over 16 periods of 5 days throughout one year. Limited forage resulted from high stocking rates and drought. This necessitated the provision of supplementary feed which was utilised solely by Merino sheep. Springbok were at all times more dispersed than Merino sheep especially so when pasture conditions deteriorated and feed was provided. Springbok preferred a ‘rand’ vegetation where favourite food plants such as Pentzia spp. and Pteronia spp. predominated. Merino sheep were largely dependent on the close proximity of feed and watering sites and exhibited a preference for a ‘pan’ vegetation. Temporal variation in these distribution patterns is discussed. Levels of association between the two species changed through the year. Observed inter-specific differences suggest that a combination would lead to a better utilisation of the vegetation.
12 citations
TL;DR: An increase in the role of the springbok in Karoo farming concurrent with Merino stock reductions is recommend to help improve productivity in this farming enterprise in the Karoo.
Abstract: SUMMARY Productivity data were collected over a period of seven years of low rainfall on a farming enterprise in the Karoo. Merino sheep were the more important component producers in this enterprise and were 46% more efficient than springbok at converting estimated food energy into net rands profit. Both springbok and Merino sheep populations exhibited recruitments in excess of 30%. Springbok had a lambing percentage of 87% compared with 75% for Merino sheep. Nearly 50% of the springbok population died as a result of critical shortage of nutrients in 1984 representing a severe loss of capital. Merino sheep incurred large feed bills. Management costs for Merino sheep were thus higher (51,1% gross income) than for springbok (31,3% gross income) resulting in a favourable contribution of springbok to net profit. Moreover, springbok were more efficient at converting food energy into kg saleable meat. An increase in the role of the springbok in Karoo farming concurrent with Merino stock reductions is recommend...
11 citations
TL;DR: In this article, the authors investigated the effect of a large artificial reef on nearby sediment distribution and associated meiofauna and found that the sand became slightly finer on the port flank, in the lee of the wave trains, compared to starboard undisturbed terrain, which they used as control.
Abstract: SUMMARY This study investigates the effect of a large artificial reef on nearby sediment distribution and associated meiofauna. Turbulence caused by prevailing swells resulted in resuspension and further size sorting of the sediment in the vicinity. The sand became slightly, but significantly, finer on the port flank, in the lee of the wave trains, compared to starboard undisturbed terrain, which we used as control. No significant difference in biogenic carbonate content could be detected with respect to the two sides, while sediment detritus was enhanced on port. Nematodes and oligochaets became significantly more abundant on port relative to starboard and the control. Overall, meiofauna standing biomass (gC. 100 ml−1 sediment) near the hull was enriched with respect to open ground. The significance of this to higher trophic levels remains unproven.
9 citations
TL;DR: Since both investigated harvesting procedures were deleterious to benthic standing stocks, it was concluded that any harvesting programme must include the conservation of undisturbed areas.
Abstract: SUMMARY A four-month study of the effects of submerged aquatic plant harvesting on invertebrate communities associated with Potamogeton pectinatus L. at Marina Da Gama, Zandvlei, is described. Fifteen taxa were recorded. Five taxa formed 78,8-99,4% of the invertebrate biomass at all three sites: Ficopomatus enigmaticus (Fauvel) > Chironomidae larvae > Ischnura senegalensis (Rambur) > Tomichia ventricosa (Rve) > Ostracoda. Total invertebrate standing stocks were higher at an unharvested site (4,63-12,65 g dry mass m−2) than at a ‘controlled-height’ harvested site (1,36-4,43 g dry mass m−2) and a regularly harvested site (1,94-7,06 g dry mass m−2). Since both investigated harvesting procedures were deleterious to benthic standing stocks, it was concluded that any harvesting programme must include the conservation of undisturbed areas.
5 citations
TL;DR: In this article, the distribution of marine species on a rocky shore at Umdoni Park was analysed objectively by a computer technique using Normal Association Analysis (NAA) and Principal Components Analysis (PCA).
Abstract: SUMMARY The distribution of marine species on a rocky shore at Umdoni Park was analysed objectively by a computer technique using Normal Association Analysis (NAA) and Principal Components Analysis (PCA). Five communities were defined and the major gradient along the two principal components axes was correlated with that sector of the shore which received wave surge every day irrespective of the state of the tide. This analysis is compared favourably with Eyre & Stephenson's (1938) zonation scheme for rocky shores of Natal. Based on physical characters Umdoni Park has a three-zone shore of which the midlittoral Ralfsia expansa community represents that sector in which many marine species have reached the upper limits of their physiological tolerance.
3 citations
TL;DR: Bullia digitalis is a sandy-beach whelk which displays a well-defined series of reactions to most pollutants, and a correlation is demonstrated between these concentrations and the first-order molecular valence connectivity indices of the substances concerned.
Abstract: SUMMARY Bullia digitalis is a sandy-beach whelk which displays a well-defined series of reactions to most pollutants. A marked sub-lethal response is cessation of burrowing, the animals either refusing to burrow or emerging from the sand if already buried. The concentrations of a series of organic substances eliciting the latter response are reported and a correlation is demonstrated between these concentrations and the first-order molecular valence connectivity indices of the substances concerned.
TL;DR: In this paper, the authors explored some of the possible applications of HPLC in the field of marine organic chemistry and suggested that the use of reverse phase (C18, C19,...
Abstract: This paper explores some of the possible applications of High Performance Liquid Chromatography (HPLC) in the field of marine organic chemistry. It is suggested that the use of reverse phase (C18, ...