Gastric evacuation, feeding periodicity and daily ration of Sardine sardinops sagax in the southern Benguela upwelling ecosystem

Laboratory and field experiments were conducted to determine gastric evacuation rates of sardine Sardinops sagax, and stomach content analyses were undertaken to assess feeding periodicity and estimate the daily ration of this species in the southern Benguela. Gastric evacuation followed an exponential pattern and was influenced by food type; phytoplankton was evacuated at a much faster rate than zooplankton. Estimated gastric evacuation rates ranged between 0.05 and 0.29.h-1, with mean values of 0.09 and 0.27.h-1 for fish fed zooplankton and phytoplankton respectively. Despite this large range, no significant relationships were found between gastric evacuation rate and fish size, temperature, food particle size or meal size. Feeding periodicity was size-dependent; small fish had a peak in feeding activity at or around sunset, whereas larger fish appeared to feed continuously. This suggests that fish of different size exhibit different foraging behaviours, possibly reflecting differences in their diets. Estimates of daily ration ranged from 0.99 to 2.52% wet body mass.day-1 for fish consuming zooplankton and from 2.97 to 7.58% wet body mass.day-1 for fish consuming phytoplankton. Small fish consumed a bigger daily ration than large fish

Diet of sardine Sardinops sagax in the southern Benguela upwelling ecosystem

The diet of sardine Sardinops sagax in the southern Benguela was investigated by microscopic examination of stomach contents. The relative dietary importance of prey size and prey type was assessed by calculating the carbon content of prey items. Sardine is an omnivorous clupeoid, ingesting both phytoplankton and zooplankton, with the relative importance of these two food types varying both spatially and temporally. Stomach contents were numerically dominated by small prey items, principally dinoflagellates, followed by crustacean eggs, cyclopoid copepods, calanoid copepods and diatoms. Virtually all prey items ingested by sardine wer

An assessment of the suitability of the galjoen, Coracinus capensis cuvier, for mariculture in South Africa

Bibliography: pages 151-184.The suitability of the galjoen, Coracinus capensis, for mariculture in South Africa has been assessed from both an economic and a biological viewpoint. In terms of economic criteria galjoen shows a high potential for culture, being widely known and highly regarded as a table fish. The restaurant trade in the southwestern Cape has been identified as a possible market showing a high demand for this species. Adult galjoen are readily available, hardy, and are easily maintained in captivity. A biochemical technique to determine the sex of live fish has been elucidated and allows sexual identification to be conducted for several months prior to and during the spawning season. Natural serial spawning with high fertilization occurs readily in captivity, with galjoen producing large numbers of good quality eggs during a single season. However induced spawning using two mammalian gonadotropins resulted in the production of poor quality eggs. The relationship between temperature and development time for fertilized galjoen eggs has been determined, and the lower lethal temperature for developing eggs was found to lie between 14° and 16°C. Newly-hatched larvae exhaust their endogenous food reserves rapidly and show a short time to irreversible starvation, with first-feeding beginning from 110 hours after hatching at 18°C. Galjoen larvae proved to be extremely difficult to rear. Although successful first-feeding on a few live food organisms was observed, mass mortality at 4-8 days and again at 12-15 days after first-feeding resulted in exceptionally poor survival. It is surmised that galjoen larvae have very stringent nutritional requirements which cannot be met by employing commonly-used live food organisms. Growth rate estimates for galjoen that survived past metamorphosis indicate that growth under culture conditions is similar to that in the natural environment. Certain biological attributes of the galjoen such as simple broodstock maintenance, ease of natural spawning in captivity and high fecundity select this species for culture. However the inability to mass rear larvae through to metamorphosis drastically reduces the suitability of this species, especially since larval rearing is the key to successful mariculture. In addition, the slow growth rate under culture conditions observed also selects against this species. Because of these last two factors, it is concluded that the galjoen is not a suitable species for mariculture in South Africa

The use of the critical path and critical chain methods in the South African construction industry

The purpose of this article is to report on an investigation of the use of critical path and critical chain methods in the South African construction industry. Through a questionnaire survey, data was collected to establish which construction sectors apply these methods, the percentage of construction professionals using these methods, the reasons why these methods are applied, and the factors that influence the use of these methods. Based on the findings, the critical path and critical chain methods are mostly used in the South African construction industry by the building sector, in comparison to the civil and industrial sectors. The critical path method is used more than the critical chain method, with over 70% of the responding companies applying the critical path method and only 22% applying the critical chain method. The latter method is considered to be a relatively new project management tool and requires a culture change in the company. Users of the critical path method believe that the method mainly improves their project understanding, planning, scheduling and control, with all these improvements ultimately leading to better on-time completion of projects and cost saving

Turbidity-induced changes in feeding strategies of fish in estuaries

The aim of this study was to determine the effect of turbidity on the feeding strategies of fish in estuaries. Three species representing different feeding guilds were selected for the investigation. These were Elops machnata (representative piscivore), Pomadasys commersonnii (a macrobenthivore) and Atherina breviceps (a planktivore). The stomach contents of these fish were examined from a clear and a turbid estuary and some experimental work was carried out on A breviceps to test the hypothesis that turbidity affects feeding behaviour. Turbidity was found to have no effect on size selection of prey, but feeding rate, particularly of visual predators, was reduced at higher turbidity levels. This was caused by a decrease in the reactive distance of the fish. It would appear that in order to optimize the aquisition of food under different turbidity conditions fishes have the ability to change their feeding strategies. Visual predators are more affected by turbidity than are macrobenthic feeders

A comparison of condition factor and gona dosomatic index of sardine Sardinops sagax stocks in the northern and southern Benguela upwelling ecosystems, 1984–1999

Time-series of condition factor (CF) and gonadosomatic index (GSI) were generated using general linear models (GLM) for sardine Sardinops sagax stocks in the northern and southern Benguela ecosystems over the period 1984–1999. During this period the biomass of sardine in the northern Benguela remained at relatively low levels of African Journal of Marine Science 2001, 23: 123–13

Aspects of coloured precious metal intermetallic compounds

This paper provides a review on coloured gold, platinum, and palladium intermetallic compounds, and discusses the models that were developed to obtain these materials. These compounds have a crystal structure of high symmetry, such as the CaF2 or CsCl structures, ensuring distinct electron band structures. Various examples of coloured gold, platinum, and palladium intermetallic compounds are provided. More in-depth discussion is provided on the purple gold (AuAl2) and yellow platinum-aluminium (PtAl2) compounds with CaF2 structure, as well as the purplish-pink palladium-indium (PdIn) compound with CsCl structure. Precious metal intermetallic compounds are used in jewellery and provide a new dimension to design. Some of these compounds have also found use as barrier coatings on turbine blades for jet engines, and more recently, research has been conducted into their potential use as catalysts, electro-catalysts, sensors, capacitors, and for decorative coatings.This paper was first presented at the, Precious Metals 2013 Conference, 14–16 October 2013, Protea Hotel, President, Cape Town, South Africa.http://www.saimm.co.za/journal-papersam201

Bone mass and bone size in 10 year-old South African children

Thesis (Ph.D.)--University of the Witwatersrand, Faculty of Health Sciences, 2012Osteoporosis has been described as a paediatric disease with geriatric consequences. This thesis explored the associations between proximal, historical and predictive genetic and environmental factors affecting bone mass and bone size in socio-economically- and environmentally-disadvantaged black and -advantaged white pre- and early-pubertal South African children. Data were collected from 476 children (182 black boys, 72 white boys, 158 black girls, 64 white girls) of mean age 10.6 years (range: 10.0-10.9), 406 biological mothers and 100 biological fathers. The main findings were that black children and their parents compared to white, had greater DXA-measured BMC at the femoral neck regardless of the way in which BMC was corrected for size (height, weight, BA and/or BAPC) and greater bone strength. Lumbar spine BMC was greater or similar depending on which measures were used to correct BMC for size. At the whole body, mid radius and distal one third of the radius, BMC varied between children, and between their parents, and were dependent on which measures were used to correct BMC for size. Weight at 1 year (WT1), length at 1 year (LT1) and birth weight (BW), were significant predictors of BMC of the femoral neck (P<0.05-0.01) after correcting BA and BMC for race/ethnicity, gender, age, socioeconomic status, bone age, height and weight at 10 years. Maternal and paternal heritability was estimated to each be ~30% in both black and white subjects. The main conclusion was that ethnicity is the single most important proximal factor affecting bone mass and bone size in 10 year old South African children. Black children demonstrate a superior bone mass and bone strength at the femoral neck. Historical and predictive factors however indicate that black children have not been programmed for optimal bone health in utero and early life, nor are contemporary environmental factors favourable for the maximisation of peak bone mass. This cohort may be at risk of developing osteoporosis as an elderly population, particularly at the lumbar spine and forearm

The Feeding ecology of, and carbon and nitrogen budgets for, sardine sardinops sagax in the Southern Benguela upwelling ecosystem

Bibliography : pages 178-202.Combined laboratory and field studies were employed to examine the feeding ecology of sardine Sardinops sagax in order to evaluate conflicting hypotheses regarding the trophic position of clupeoids in upwelling ecosystems, and to compare the trophodynamics of sardine with those of the co-occurring anchovy Engraulis capensis. Carbon and nitrogen budget models constructed using data from these studies were used to quantify the effect of particular food environments upon sardine growth. Sardinops sagax is primarily a filter-feeder, with food particles <1230μm total length eliciting a filtering response while larger particles elicit particulate-feeding at low concentrations and filter-feeding at high concentrations. This species is able to retain cells as small as 13μm, feeds at near-maximum efficiency when filterfeeding, and displays size-selectivity during particulate-feeding. Significant linear relationships between respiration rate and swimming speed obtained for sardine demonstrate that filter-feeding is the most energetically cheap feeding mode. Although omnivorous, sardine absorbs carbon and nitrogen more efficiently from zooplankton than from phytoplankton. Gastric evacuation follows an exponential pattern in sardine, and is influenced by food type; phytoplankton is evacuated faster than zooplankton. Feeding periodicity in sardine is size dependent; small fish show a feeding peak at, or around, sunset whereas larger fish appear to feed continuously. Estimates of daily ration range between 0.99 to 7.58% wet body mass.d-¹, depending on fish size and food type. Sardine stomach contents are numerically dominated by small particles, principally dinoflagellate phytoplankton, but the majority of the sardine's dietary carbon is derived from zooplankton, principally small calanoid and cyclopoid copepods. The budget models indicate that sardine is capable of positive growth under most of the trophic conditions it is likely to encounter in the southern Benguela upwelling system. The classical hypothesis that the high abundance of clupeoids in upwelling ecosystems results from their phytophagy is rejected; like anchovy, sardine are primarily zoophagous. However, these two species are trophodynamically distinct and show resource partitioning on the basis of prey size; sardine consume small zooplankton whilst anchovy consume large zooplankton. This difference is likely to contribute to regime shifts observed between these two species