Occurrence of tuna and mackerel larvae (Family: Scombridae) off the east coast of South Africa

2000 ◽  
Vol 51 (8) ◽  
pp. 777 ◽  
Author(s):  
Lynnath E. Beckley ◽  
Jeff M. Leis
Keyword(s):  
South Africa ◽  
East Coast ◽  
Temporal Distribution ◽  
Western Indian Ocean ◽  
Distribution Patterns ◽  
Agulhas Current ◽  
The North ◽  
Scomberomorus Commerson ◽  
Euthynnus Affinis ◽  
King Mackerel

Spatial and temporal distribution patterns of scombrid larvae along the east coast of South Africa were investigated from ichthyoplankton collections made during May–June 1990 (winter), October 1990 (spring) and February 1991 (summer). Results were analysed in relation to oceanographic conditions and known spawning localities of tuna and mackerels in the western Indian Ocean. In total, eight species were represented in the samples, with highest diversity in February and lowest numbers in May–June. Larvae of the temperate chub mackerel Scomber japonicus were most abundant at shelf stations during October. Larvae of neritic tunas Auxis sp. and Euthynnus affinis occurred in shelf stations off KwaZulu–Natal in February and extended southward in a plume along the shelf edge. Larvae of skipjack tunaKatsuwonus pelamis were most abundant in the Agulhas Current during February. Only a few larvae of oceanic tunas Thunnus spp., wahoo Acanthocybium solandri and king mackerel Scomberomorus commerson were collected in the Agulhas Current in the north of the study area during February when there was an intrusion of warm Tropical Surface Water. This indicates that spawning of these species probably does not occur off the east coast of South Africa.

Sea-level related molluscan plankton events (Gastropoda, Euthecosomata) during the Rupelian (Early Oligocene) of the North Sea Basin

2004 ◽  
Vol 83 (3) ◽  
pp. 199-208
Author(s):  
K. Gürs ◽  
A.W. Janssen
Keyword(s):  
Sea Level ◽  
North Sea ◽  
Temporal Distribution ◽  
Distribution Patterns ◽  
Short Term ◽  
The North ◽  
Early Oligocene ◽  
The North Sea

AbstractSpacio-temporal distribution patterns of North Sea Basin Early Oligocene (Rupelian) pteropoda (holoplanktonic gastropods: Mollusca, Gastropoda, Euthecosomata) are studied. These patterns indicate three short term invasions of a single pteropod species during the Rupelian. These invasions are indicated here as Clio blinkae Event, Praehyalocylis laxeannulata Event and Clio jacobae Event. The conspicuously short occurrences of the species, their abundances and some lithological features of the pteropod bearing strata lead to the conclusion that these plankton events are linked to sea level high-stands allowing currents from the worlds oceans to enter into the North Sea Basin.

scholarly journals Ocean Gliders Ride the Research Wave in the Agulhas Current

Eos ◽  
2018 ◽  
Vol 99 ◽  
Author(s):  
Marjolaine Krug ◽  
Sebastiaan Swart ◽  
Juliet Hermes
Keyword(s):  
South Africa ◽  
East Coast ◽  
Agulhas Current

Off the east coast of South Africa, robotic ocean gliders deployed in the Agulhas Current capture new data that help us better understand how energy dissipates in the ocean.

scholarly journals Opportunistically collected data from aerial surveys reveal spatio-temporal distribution patterns of marine debris in German waters

2020 ◽  
Vol 28 (3) ◽  
pp. 2893-2903
Author(s):  
Bianca Unger ◽  
Helena Herr ◽  
Sacha Viquerat ◽  
Anita Gilles ◽  
Patricia Burkhardt-Holm ◽  
...  
Keyword(s):  
Temporal Distribution ◽  
Distribution Patterns ◽  
Aerial Survey ◽  
Marine Debris ◽  
Encounter Rate ◽  
The North ◽  
Aerial Surveys ◽  
Spatio Temporal ◽  
German Waters ◽  
The Baltic

AbstractMarine debris is known for its ubiquitousness and harmful effects on marine life. This study is the first analysis to provide information on the distribution of floating marine debris in German waters using aerial survey data collected between 2002 and 2016. During regular harbour porpoise monitoring flights, 191,167 km were covered and 26,512 floating debris items recorded (average encounter rate 0.1387 items/km). Debris was encountered more often in the North Sea than in the Baltic Sea (0.16 items/km; 0.08 items/km). The average encounter rate was higher in offshore waters than in coastal areas. Overlaps of marine debris distribution with ‘Special Areas of Conservation’ are a particular reason for concern. Moreover, the spring months (March–May) were identified to be the time of the year with the highest average encounter rates for marine debris. Fishing-related debris was shown to contribute up to 25% of the total number of all observed items. This study shows that opportunistically collected data on marine debris from aerial surveys are valuable for identifying distribution patterns of floating debris without additional survey effort and costs. These data can be used as baseline information to inform management schemes such as the Marine Strategy Framework Directive.

The influence of urban built environment on residential burglary in China: Testing the encounter and enclosure hypotheses

2019 ◽  
pp. 174889581987486 ◽  
Author(s):  
Han Yue ◽  
Xinyan Zhu
Keyword(s):  
Built Environment ◽  
Spatial Regression ◽  
Housing Prices ◽  
Temporal Distribution ◽  
Distribution Patterns ◽  
Time Of Day ◽  
Residential Burglary ◽  
North West ◽  
The North ◽  
Residential Burglaries

It is widely recognized that crimes are clustered in space. Features of the built environment are among various factors associated with crime clustering patterns. There are two competing perspectives on this association: the “encounter” and “enclosure” hypotheses. This study examines the effect of the built environment on the spatial distribution of residential burglary in Wuhan, China, aiming to test these two competing perspectives. First, we review existing studies analyzing the influence of the built environment on residential burglary, especially those based on the two hypotheses. We then conduct an exploratory data analysis to observe the spatial and temporal distribution patterns of residential burglaries. Next, we use a multivariate spatial regression model to evaluate the influence of various built environment characteristics on residential burglaries, after controlling for socio-demographic variables, guardianship, and the time-of-day effect. The results suggest a double peak in the hourly distribution of burglaries: 6:00 a.m.–8:59 a.m. and 5:00 p.m.–7:59 p.m. Burglaries are positively and significantly autocorrelated in space and mainly concentrated in the north-west and central areas of Wuhan. Two transport facilities features (intersection density and the presence of subway stations), three building features (multiple stories, high housing prices, and older houses), and land-use mix are each positively correlated with burglary. However, the burglary count is negatively correlated with the ratio of the residential land. Overall, neighborhoods with high permeability are vulnerable to residential burglaries. Thus, the principle of access control promoted by the enclosure hypothesis appears effective in preventing residential crime. The results’ implications for crime prevention and urban design practice are also discussed.

scholarly journals Seasonal and diurnal variation of lightning activity over southern Africa and correlation with European whistler observations

2006 ◽  
Vol 24 (2) ◽  
pp. 529-542 ◽  
Author(s):  
A. B. Collier ◽  
A. R. W. Hughes ◽  
J. Lichtenberger ◽  
P. Steinbach
Keyword(s):  
South Africa ◽  
Diurnal Variation ◽  
Southern Africa ◽  
Seasonal Variations ◽  
East Coast ◽  
Lightning Activity ◽  
Agulhas Current ◽  
Statistical Pattern ◽  
Seasonal And Diurnal Variation ◽  
Imaging Sensor

Abstract. Lightning Imaging Sensor (LIS) data have been analysed to ascertain the statistical pattern of lightning occurrence over southern Africa. The diurnal and seasonal variations are mapped in detail. The highest flash rates (107.2 km-2 y-1) occur close to the equator but maxima are also found over Madagascar (32.1 km-2 y-1) and South Africa (26.4 km-2 y-1). A feature of the statistics is a relatively steady contribution from over the ocean off the east coast of South Africa that appears to be associated with the Agulhas current. Lightning statistics are of intrinsic meteorological interest but they also relate to the occurrence of whistlers in the conjugate region. Whistler observations are made at Tihany, Hungary. Statistics reveal that the period of most frequent whistler occurrence does not correspond to the maximum in lightning activity in the conjugate region but is strongly influenced by ionospheric illumination and other factors. The whistler/flash ratio, R, shows remarkable variations during the year and has a peak that is narrowly confined to February and March.

Cymbastela sodwaniensis sp. nov. (Halichondrida: Axinellidae): a first record of this sponge genus in South Africa

2009 ◽  
Vol 89 (8) ◽  
pp. 1679-1687
Author(s):  
Toufiek Samaai ◽  
Ruwen Pillay ◽  
Michelle Kelly
Keyword(s):  
South Africa ◽  
New Species ◽  
Indian Ocean ◽  
Southern Africa ◽  
East Coast ◽  
First Record ◽  
North East ◽  
The North ◽  
The Indian Ocean

Cymbastela sodwaniensis sp. nov. (order Halichondrida: family Axinellidae) is described from the subtropical waters of Sodwana Bay on the north-east coast of South Africa. The genus was previously unknown from southern Africa or the western and eastern parts of the Indian Ocean. This record represents the westernmost extent of this predominantly Indo-Pacific to Australasian genus. This new species record brings the number of Cymbastela species described to a total of nine.

Impact of Climate Change on the Agulhas Bank, South Africa ― a 100 year projection with consequences for the squid fishery

2020 ◽  
Author(s):  
Sarah Asdar ◽  
Michael J. Roberts ◽  
Zoe Jacobs ◽  
Ekaterina Popova
Keyword(s):  
Climate Change ◽  
South Africa ◽  
Water Retention ◽  
East Coast ◽  
Surface Current ◽  
Economic Importance ◽  
Economic Consequences ◽  
Local Circulation ◽  
Agulhas Current ◽  
Ocean Biogeochemistry

<p>The South and East coast of South Africa is strongly influenced by the warm, fast-flowing Agulhas Current. The Agulhas Bank, a shallow shelf on the southern tip of Southern Africa, is a crucial area for productivity which support fisheries of high economic importance for South Africa.  In this context of climate change, perturbations of this diverse, complex and highly variable marine environment could affect the productivity and lead to dramatic social and economic consequences for the region. To predict potential changes over the eastern and central Bank, we employ a high-resolution global coupled ocean-biogeochemistry model, NEMO-MEDUSA, simulated to year 2099. We find that even though the Agulhas Bank is warming over the next century, primary production does not experience a significant decrease. Additionally, we show that the Agulhas Current might shift its position, with intensification surface current velocity on the Bank hence reducing water retention over the Bank. This change in local circulation over the Bank could have a serious impact on the ecosystem of the region.</p>

Spatial and seasonal distribution patterns of juvenile and adult raggedtooth sharks (Carcharias taurus) tagged off the east coast of South Africa

2007 ◽  
Vol 58 (1) ◽  
pp. 127 ◽  
Author(s):  
M. L. Dicken ◽  
A. J. Booth ◽  
M. J. Smale ◽  
G. Cliff
Keyword(s):  
South Africa ◽  
East Coast ◽  
Average Rate ◽  
Anthropogenic Activities ◽  
Average Distance ◽  
Movement Patterns ◽  
Release Site ◽  
Distribution Patterns ◽  
Juvenile Sharks ◽  
Carcharias Taurus

Understanding the movement patterns of raggedtooth sharks (Carcharias taurus) is crucial in defining habitat use and evaluating the effects of exploitation and anthropogenic activities. Between 1984 and 2004, 1107 C. taurus juveniles (<1.8-m TL) and 2369 C. taurus maturing subadults and adults (>1.8-m TL) were tagged and released along the east coast of South Africa. In total, 125 C. taurus juveniles and 178 C. taurus maturing subadults and adults were recaptured, representing recapture rates of 11.2% and 7.5% respectively. The average distance travelled by juvenile sharks was 18.7 km (95% CI = 10.8–26.6 km). Juvenile sharks displayed site fidelity to summer nursery areas. The average distance travelled by maturing and adult sharks was 342 km (95% CI = 275–409 km). One female shark, however, was recaptured 1897 km from its original release site. The average rate at which pregnant sharks moved south from their gestation to pupping grounds was 2.6 km day–1 (95% CI = 2.04–3.16 km day–1). This study highlights the differences in movement patterns between C. taurus juveniles and adults and suggests philopatric behaviour in both life-history stages.

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