The biomass and ecology of chokka squid Loligo vulgaris reynaudii off the West Coast of South Africa

Migration, stock size and ecology of chokka squid Loligo vulgaris reynaudii off the West Coast of South Africa were studied and their relationship to other regions compared by analysis of distributional, biomass, and size composition, and biological data collected from biannual research cruises from 1983-1987. Biomass was lower than on the South Coast, higher in summer than in winter and declined over the duration of the study. The distribution of squid was generally continuous from the east up to between Cape Point and Cape Columbine. North of Cape Columbine it was more sporadic and occurred only occasionally in the far north (north of 31°S). Depth distribution, at up to 350 m, was much greater than on the S. Coast where an insignificant percentage of the biomass occurs over 200 m. The size composition was unimodal compared to a polymodal distribution on the S. Coast, and mean and modal sizes were smaller. Maturity rates and gonado-somatic indices were also much lower. The percentage of feeding squid was, however, considerably higher. These findings, together with distributional and commercial catch data, showed that cyclic immigration and emigration occurs between the two areas, probably to enable subadult squid to exploit the good foraging opportunities on the W. Coast. A multiple correlation analysis and regression model showed that catches were correlated with a combination of bottom depth, bottom temperatures and bottom oxygen levels. Bottom temperatures of below 8°C and bottom oxygen levels of below 3,5 ml-1 appeared to represent important limiting factors in the distribution

First study on the ecology of Sepia australis in the Southern Benguela Ecosystem

Sepia australis is most abundant in the eastern South Atlantic between Luderitz and St. Helena Bay (about 27-35°S in 100-200m). There seems to be no link between the variation in abundance of S. australis and that of its most important predator, the shallow-water Cape hake, Merluccius capensis. The variations in abundance of S. australis and one of its most important prey species, the stomatopod crustacean Pterygosquilla armata capensis, show simultaneous changes, suggesting that both species respond to the same environmental factors. Mantle length, total weight, gonad weight, and sex ratio of Sepia australis vary from year to year and by region off the west coast of southern Africa. Animals from the south coast (eastward of Cape Point) were very different: length-weight relationhips were found to be similar in slope and intercept for both sexes and within each sex between years and regions off the west coast, but different for the south coast

The biomass and ecology of chokka squidLoligo vulgaris reynaudiioff the West Coast of South Africa

Migration, stock size and ecology of chokka squid Loligo vulgaris reynaudii off the West Coast of South Africa were studied and their relationship to other regions compared by analysis of distributional, biomass, and size composition, and biological data collected from biannual research cruises from 1983-1987. Biomass was lower than on the South Coast, higher in summer than in winter and declined over the duration of the study. The distribution of squid was generally continuous from the east up to between Cape Point and Cape Columbine. North of Cape Columbine it was more sporadic and occurred only occasionally in the far north (north of 31°S). Depth distribution, at up to 350 m, was much greater than on the S. Coast where an insignificant percentage of the biomass occurs over 200 m. The size composition was unimodal compared to a polymodal distribution on the S. Coast, and mean and modal sizes were smaller. Maturity rates and gonado-somatic indices were also much lower. The percentage of feeding squid was, however, considerably higher. These findings, together with distributional and commercial catch data, showed that cyclic immigration and emigration occurs between the two areas, probably to enable subadult squid to exploit the good foraging opportunities on the W. Coast. A multiple correlation analysis and regression model showed that catches were correlated with a combination of bottom depth, bottom temperatures and bottom oxygen levels. Bottom temperatures of below 8°C and bottom oxygen levels of below 3,5 ml.1-1 appeared to represent important limiting factors in the distribution. Trekgewoontes, stapelgrootte en die ekologie van die tjokka Loligo vulgaris reynaudii aan die Weskus van Suid-Afrika is bestudeer en verwantskappe met ander gebiede vergelyk aan die hand van ontleding van verspreidings-, biomassa-, grootteverspreidings-en biolog ¡ese data wat twee maal jaarliks tussen 1983 en 1987 versamei is. Biomassa was laer as aan die Suidkus, hoër in die somer as gedurende die winter en biomassaskattings het tydens die studie gedaal. Die verspreiding van tjokka was oor die algemeen aaneenlopend vanaf die ooste tot tussen Kaappunt en Kaap Columbine. Noord van Kaap Columbine was dit meer sporadies, en het slegs af en toe in die verre noorde (noord van 31 °S) voorgekom. Diepteverspreiding was tot 350 m, heel wat dieper as aan die Suidkus waar 'n onbeduidende persentasie van die biomassa dieper as 200 m voorkom. Die grootteverspreiding was unimodaal vergeleke met 'n polimodale verspreiding aan die Suidkus, en gemiddelde en modale groottes was kleiner. Die mate van geslagsrypheid en gonado-somatiese indekse was ook baie laer. Voedingstempos was egter heelwat hoër. Hierdie bevindings, tesarne met verspreidings-en vangsdata, het daarop gedui dat daar 'n sikliese immigrasie en emigrasie tussen die twee gebiede plaasvind, waarskynlik sodat voorvolwasse pylinkvis die goeie voedingspotensiaal aan die Weskus kan benut, 'n Meerveranderlike korrelasie-analise en regressiemodel het bewys dat vangste gekorreleerd was met 'n kombinasie van bodemdiepte, bodemtemperatuur en bodemsuurstofvlakke. Bodemtemperatuur onder 8°C en bodemsuurstofvlakke onder 3,5 ml.l-1 is blykbaar belangrike fakore wat beperkend inwerk op verspreiding

Distribution and abundance of Sepioidea off South Africa

The distribution and abundance of six species of Sepia and one of Rossia were studied during six west coast and three south coast bottom trawl surveys off South Africa. The two most common species on both coasts were Sepia australis and S. hieronis. Both were most abundant on the northern West Coast (Orange River and Port Nolloth areas) and were sparsely ditributed over the rest of the region. The depths of greatest abundance were 60-190m (S. australis) and 110-250m (S. hieronis). The highest biomass indices were recorded on the species also peaked in May 1988 on the South Coast (803 tons). The environmental factors most influencial in the distribution of the two species were bottom oxygen concentrations between 1,5 and 3,5ml-l-1. The two species were most abundant at relatively low temperatures: on the West Coast catches peaked when the S. simoniana and S. typica) are usually found in shallow water (<100m), mainly on the South Coast. Rossia enigmatica, a sepiolid, is most abundant in 400-500m of water, generally on the West Coast

Flavour Components of Whiskey. II Ageing Changes in the High-Volatility Fraction

The volatile compounds isolated from whiskey by fractional vacuum distillation were identified by two-dimensional capillary gas chromatography/mass spectrometry. Changing levels with ageing were quantified for the most abundant compounds by direct split injection of whiskeys on a gas chromatograph equipped with a flame ionisation detector. The ageing decreases in volatile sulfides were similarly determined using a sulfur chemiluminescence detector. Large volume headspace injection sufficiently reproduced the distillation enrichment to allow direct twodimensional determination of similar ageing changes for other trace compounds. Seven compounds at μg/L and low mg/L levels were monitored and quantified

Flavour Components of Whiskey. I. Distribution and Recovery of Compounds by Fractional Vacuum Distillation

A vacuum fractional distillation procedure is described for separating both the matrix components and flavour compounds of a whiskey into well-defined groups based on differences in azeotropic boiling points. The distillation was carried out at near ambient temperatures to accommodate both unaged and aged whiskies. Analytical and sensory data indicated good recovery of congeners. Individual fractions were reconstituted with ethanol and water to the original volume and strength dimensions of the whiskey. Undesirable thermal changes in the aged products were minimised by the low temperature fractionation and allowed changes in the flavour composition of whiskey due to maturation to be investigated for such unaged and aged reconstituted pairs

Die opleiding van bedryfsielkundiges in Suid-Afrika.

Oor die afgelope aantal jare het bedryfsielkundiges in Suid-Afrika by verskeie geleenthede die mening gelug dat die tyd waarskynlik aangebreek het om die ontwikkeling van hul vakgebied hier te lande in oënskou te neem. Hierdie behoefte het klaarblyklik ontstaan vanweë die snelle ontwikkeling wat die bedryfsielkunde die afgelope 10 tot 15 jaar in Suid-Afrika ondergaan het, vernaamlik in die praktiese beroeps- en bedryfslewe, aan akademiese instellings en in die beoefening van die bedryfsielkunde as 'n professie

Flavour Components of Whiskey. III. Ageing Changes in the Low-Volatility Fraction

The low-volatility wood-originating compounds isolated from whiskey by vacuum fractional distillation were analysed by high-resolution gas chromatography and mass spectrometry (GC-MS). Three phenolic esters previously unreported in whiskey were identified and confirmed by synthesis. Formation profiles for sixteen compounds were established in whiskeys aged for periods from 1.5 to 10 years in second-fill heavy-charred American Bourbon barrels.  These profiles indicated significant increases for several compounds, especially in the older whiskeys. Ratios of aromatic phenolic aldehydes, and similar ratio changes during ageing, were different from reported data relating to other wood types and treatments. Further preparative separation by high-pressure liquid chromatography (HPLC) of the wood fraction followed by GC-MS allowed retention and mass spectral characterisation of additional compounds originating from wood. Sensory investigation indicated different and unique contributions from the HPLC cuts. Spiking of the three phenolic esters into a young whiskey gave a detectable increase in maturation intensity

Marine fisheries monitoring programmes in South Africa

South Africa was an early leader in multidisciplinary studies of marine resources, particularly with the Benguela Ecology Programme in the 1980s and 1990s and catch records are available for some species dating back more than a century. Resources data have focused on trends in catches, fishing effort and changes in distribution and abundance of harvested resources, which often account for a major part of the structure and functioning of marine ecosystems. Data have been collected by means of fishery-dependent and fishery-independent survey techniques appropriate to each particular stock and analysed using traditional single species stock assessment techniques. The data are complemented by comprehensive information on the environment and top predators and have been analysed using trophodynamic models such as Ecopath with Ecosim. Future approaches include a shift to an ecosystem approach to fisheries monitoring and management, in an attempt to reconcile utilisation and biodiversity conservation objectives. Despite these scientific achievements, the single species approach to the management of most resources still persists, with only limited interactions between competing species or predators and prey being formally taken into account when modelling the stock dynamics and providing management advice to the authorities