Sessile biofouling on tags from recaptured raggedtooth sharks (Carcharias taurus) and their effects on tagging studies

2011 ◽  
Vol 62 (4) ◽  
pp. 359 ◽  
Author(s):  
M. L. Dicken ◽  
S. Parker Nance ◽  
M. J. Smale
Keyword(s):  
South Africa ◽  
Calcium Carbonate ◽  
Significant Relationship ◽  
Taxonomic Group ◽  
Eastern Coast ◽  
Wet Weight ◽  
Inherent Problem ◽  
Fish Tagging ◽  
Sessile Organisms ◽  
Carcharias Taurus

Biofouling of external tags can damage both the animal and the tag. It is an inherent problem to many fish-tagging studies; however, it has received little attention. Between 2005 and 2007, we investigated the taxonomic group and wet weight of sessile multicellular eukaryonts growing on 33 B-type dart tags recaptured from raggedtooth sharks (Carcharias taurus Rafinesque, 1810) along the eastern coast of South Africa. All tags, except one from a shark that had been at liberty only for 13 days, contained some degree of macro-fouling that ranged from 0.031 to 7.687 g wet weight. Barnacles and hydroids were the first colonisers and were recorded on tags after only 47 days. Bivalves, polychaetes and algae succeeded within 60 days. The last two taxa to be recorded were ascidians and sponges. There was no significant relationship between either the biomass of sessile organisms (P = 0.17) or the number of taxa (P = 0.59) found growing on tags and their time at liberty. Calcium carbonate plugs, ranging in weight from 0.16 to 9.18 g, were found at the site of the tag insertion wound on 27.3% of recaptures. The present study highlights the extent of biofouling growth on tags and its potential to bias results from tagging studies.

Possible maternal offloading of metals in the plasma, uterine and capsule fluid of pregnant ragged-tooth sharks (Carcharias taurus) on the east coast of South Africa

2017 ◽  
Vol 24 (20) ◽  
pp. 16798-16805 ◽  
Author(s):  
Kristina Naidoo ◽  
Anil Chuturgoon ◽  
Geremy Cliff ◽  
Sanil Singh ◽  
Megan Ellis ◽  
...  
Keyword(s):  
South Africa ◽  
East Coast ◽  
Carcharias Taurus

Generic reclassification of species formerly included in Rhantus Dejean (Coleoptera, Dytiscidae, Colymbetinae)

Zootaxa ◽  
2017 ◽  
Vol 4258 (1) ◽  
pp. 91 ◽  
Author(s):  
MICHAEL BALKE ◽  
JIŘÍ HÁJEK ◽  
LARS HENDRICH
Keyword(s):  
South Africa ◽  
New York ◽  
New York City ◽  
Phylogenetic Analysis ◽  
York City ◽  
Neotropical Region ◽  
Eastern Coast ◽  
New Genera ◽  
Far North ◽  
Molecular Phylogenetic

A reclassification of several species traditionally included in Rhantus Dejean, 1833 is given: Nartus Zaitzev, 1907 is re-instated as genus with one species in the Nearctic and one in the Palaearctic region; two new genera are erected: Meri-diorhantus n. gen., with M. antarcticus (Germain, 1854) n. comb., M. calidus (Fabricius, 1792) n. comb., M. limbatus (Aubé, 1838) n. comb., M. orbignyi (Balke, 1992) n. comb., M. validus (Sharp, 1882) n. comb. in the Neotropical region (M. calidus also in the southern USA and along the eastern coast as far north as New York City), and the monotypic Caperhantus n. gen., with C. cicurius (Fabricius, 1787) n. comb. in south Africa. Furthermore, nine Pacific and Australian Rhantus are transferred to the genus Carabdytes Balke, Hendrich & Wewalka, 1992: C. alutaceus (Fauvel, 1883) n. comb., C. guadalcanalensis (Balke, 1998) n. comb., C. monteithi (Balke, Wewalka, Alarie & Ribera, 2007) n. comb., C. novaecaledoniae (J. Balfour-Browne, 1944) n. comb., C. oceanicus (Balke, 1993b) n. comb., C. pacificus (Boisduval, 1835) n. comb., C. plantaris (Sharp, 1882) n. comb., C. poellerbauerae (Balke, Wewalka, Alarie & Ribera, 2007) n. comb. and C. pseudopacificus Balke, 1993b) n. comb. All changes are based on a previous comprehensive molecular phylogenetic analysis of Colymbetinae. Diagnostic characters are given for all genera mentioned above and each of them is illustrated with one or more habitus pictures. An updated key to all genera of Colymbetinae is also given. 

scholarly journals A globally threatened shark, Carcharias taurus, shows no population decline in South Africa

2020 ◽  
Vol 10 (1) ◽  
Author(s):  
Juliana D. Klein ◽  
Aletta E. Bester-van der Merwe ◽  
Matthew L. Dicken ◽  
Arsalan Emami-Khoyi ◽  
Kolobe L. Mmonwa ◽  
...  
Keyword(s):  
South Africa ◽  
Census Data ◽  
Demographic History ◽  
Conservation Status ◽  
Population Decline ◽  
Multilocus Genotype ◽  
Population Declines ◽  
Effective Population ◽  
Anthropogenic Pressures ◽  
Carcharias Taurus

Abstract Knowledge about the demographic histories of natural populations helps to evaluate their conservation status, and potential impacts of natural and anthropogenic pressures. In particular, estimates of effective population size obtained through molecular data can provide useful information to guide management decisions for vulnerable populations. The spotted ragged-tooth shark, Carcharias taurus (also known as the sandtiger or grey nurse shark), is widely distributed in warm-temperate and subtropical waters, but has suffered severe population declines across much of its range as a result of overexploitation. Here, we used multilocus genotype data to investigate the demographic history of the South African C. taurus population. Using approximate Bayesian computation and likelihood-based importance sampling, we found that the population underwent a historical range expansion that may have been linked to climatic changes during the late Pleistocene. There was no evidence for a recent anthropogenic decline. Together with census data suggesting a stable population, these results support the idea that fishing pressure and other threats have so far not been detrimental to the local C. taurus population. The results reported here indicate that South Africa could possibly harbour the last remaining, relatively pristine population of this widespread but vulnerable top predator.

scholarly journals Preliminary observations of tag shedding, tag reporting, tag wounds, and tag biofouling for raggedtooth sharks (Carcharias taurus) tagged off the east coast of South Africa

2006 ◽  
Vol 63 (9) ◽  
pp. 1640-1648 ◽  
Author(s):  
M.L. Dicken ◽  
A.J. Booth ◽  
M.J. Smale
Keyword(s):  
South Africa ◽  
East Coast ◽  
Telephone Survey ◽  
Total Length ◽  
Significant Difference ◽  
Juvenile Sharks ◽  
Carcharias Taurus ◽  
Tag Shedding

Abstract A double-tagging experiment and integrated on-site questionnaire and telephone survey were used to investigate aspects of tag shedding, tag reporting, tag wounds, and tag biofouling for the raggedtooth shark (Carcharias taurus), tagged off the east coast of South Africa. Between 2002 and 2004, 84 juvenile (<1.8 m total length, TL), and 24 adult (>1.8 m TL) C. taurus were double-tagged. Of these, 11 juvenile and six adult double-tagged sharks were recaptured. Significantly, more tags were shed from adult than from juvenile sharks, and there was also a significant difference between the number of anterior and posterior tags shed. Rates of tag reporting were estimated from a survey of 477 randomly selected shore-anglers, and they varied both temporally and spatially from 27% to 100%. In all, 93 tag recaptures were reported in the survey, most (75.3%) with some biofouling. Tag-inflicted damage was reported in 35.5% of recaptured sharks, and the incidence of tag-inflicted damage was greater for disk (77.8%) than for dart tags (25.3%).

scholarly journals Psychological capital, job demands and organisational commitment of employees in a call centre in Durban, South Africa

2014 ◽  
Vol 14 (1) ◽  
Author(s):  
Kreshona Pillay ◽  
Johanna H. Buitendach ◽  
Herbert Kanengoni
Keyword(s):  
South Africa ◽  
Significant Relationship ◽  
Predictive Value ◽  
Psychological Capital ◽  
Job Demands ◽  
Cross Sectional Study ◽  
Medium Effect ◽  
Call Centre ◽  
Organisational Commitment ◽  
Cross Sectional

Orientation: The South African call centre industry is growing as call centres are increasingly used as a means of service delivery to customers. Positive psychologists posit that psychological capital could lead to positive outcomes such as organisational commitment of call centre staff.Research purpose: This study investigated the relationship between psychological capital, job demands and organisational commitment and intended to determine whether psychological capital and job demands predict call centre employees’ organisational commitment.Motivation for the study: The study aimed to explore potential links between psychological capital, job demands and organisational commitment of call centre employees. It is premised on previous research that call centre job demands may be related to commitment to the organisation.Research approach, design and method: This cross-sectional study sampled 117 call centre employees from Durban, South Africa, and used a biographical questionnaire, psychological capital questionnaire, the job-demands-resources scale and the organisational commitment questionnaire to collect data.Main findings: Findings indicated a statistically significant relationship between psychological capital and work overload, as well as a practically and statistically significant relationship (medium effect) between psychological capital and continuance organisational commitment. The results showed that psychological capital has predictive value for continuance organisational commitment.Practical/managerial implications: Psychological capital has predictive value for continuance organisational commitment. Organisations can develop initiatives to enhance positive psychological states and address this relationship.Contribution: The findings could be beneficial to management and employees in considering ways to boost psychological capital in order to improve organisational commitment.

scholarly journals A preliminary fish survey of the estuaries on the south-east coast of South Africa, Kei Estuary to Mdumbi: A comparative study

Water SA ◽  
2020 ◽  
Vol 46 (3 July) ◽  
Author(s):  
NC James ◽  
TD Harrison
Keyword(s):  
South Africa ◽  
Significant Relationship ◽  
East Coast ◽  
Multivariate Analyses ◽  
Fish Communities ◽  
Chemical Characteristics ◽  
The South ◽  
Physico Chemical ◽  
Biogeographic Region ◽  
Warm Temperate

A preliminary ichthyofaunal and physico-chemical survey of estuaries on the south-east coast of South Africa from the Kei Estuary to the Mdumbi Estuary was undertaken between October and November 1997. Twenty-seven (27) estuaries were surveyed along this stretch of coastline and these were grouped into three estuary types: small (< 10 ha) predominantly closed estuaries, moderate to large (> 10 ha) predominantly closed estuaries and predominantly open estuaries. Multivariate analyses revealed significant differences between predominantly closed estuaries and predominantly open estuaries in terms of both their physico-chemical characteristics and their fish communities. There was no difference between small and moderate to large predominantly closed estuaries.  A significant relationship was also observed between the physico-chemical characteristics of the estuaries and their fish communities.  The estuaries in the study area fall within the warm-temperate biogeographic region; temperate species dominated the fish communities of all the estuaries. This survey represents one of the few fish surveys undertaken along this little-studied section of the coastline. 

scholarly journals An Investigation of the Dynamic Effect of Foreign Direct Investment (FDI) and Interest Rates on GDP in South Africa

2018 ◽  
Vol 10 (5(J)) ◽  
pp. 29-37
Author(s):  
Thomas Habanabakize ◽  
Daniel F Meyer
Keyword(s):  
Economic Growth ◽  
South Africa ◽  
Foreign Direct Investment ◽  
South African ◽  
Significant Relationship ◽  
Direct Investment ◽  
Positive Relationship ◽  
Positive Impact ◽  
Long Run ◽  
Repo Rate

Economic growth in South Africa has been in the “doldrums” for the past decade. If well managed, foreign direct investment (FDI) and repo rate (interest rate) could have a positive impact and assist in rapid economic growth so urgently needed in South Africa. FDI has been a driving force for growth in many developing economies. Not enough has been done to attract FDI in South Africa. The country has enormous ability and capacity to attract FDI inflows and to have the advantages from it. A quantitative research approach was used to analyse the association amongst the variables which include FDI, GDP and repo rate in the South African economy. The South African Reserve Bank database was used and the period analysed is from 2000 to 2016. Statistical and econometric methods such as correlation analysis, unit root tests, ARDL Bounds test for cointegration, an error correction model (ECM), and the Granger causality tests were used. Subsequently, after the econometric model was estimated, findings indicated the existence of a long-run relationship between the three variables. While, a significant positive relationship exists between FDI and GDP, a negative long-run relationship was found between GDP and repo rate and interestingly a nonsignificant relationship between repo rate and FDI. In the short run, the positive effect of FDI on GDP is minimal whilst a significant and positive relationship exists between GDP and repo rate. The results did also show some limitations in the results, with regards to FDI and repo rate that there is no significant relationship between the variables, meaning that repo rate does not have an impact on FDIs. Although some long-run evidence was found of FDI playing a role in economic growth in South Africa, such impact is limited. Also very interesting is that the repo rate and FDI do not have a statistically significant relationship. This could be due to the rising risks associated with investments in the country. In conclusion, there are many variables which could have a positive impact on the attraction of FDIs and such factors will be explored further in future studies. 

Estimates of juvenile and adult raggedtooth shark (Carcharias taurus) abundance along the east coast of South Africa

2008 ◽  
Vol 65 (4) ◽  
pp. 621-632 ◽  
Author(s):  
Matthew Laurence Dicken ◽  
Anthony John Booth ◽  
Malcolm John Smale
Keyword(s):  
South Africa ◽  
East Coast ◽  
Adult Survival ◽  
Juvenile Survival ◽  
Tag Loss ◽  
Oceanographic Research ◽  
The Mean ◽  
Juvenile Sharks ◽  
Carcharias Taurus ◽  
Probability Of Capture

A Cormack–Jolly–Seber model was developed to estimate abundance, survival, and probability of capture for juvenile (<1.8 m total length, TL) and adult (>1.8 m TL) raggedtooth sharks (Carcharias taurus) along the east coast of South Africa. Model estimates were adjusted to account for tag loss, nonreporting, and after release mortality. The model was constructed using mark–recapture data from the Oceanographic Research Institute and Port Elizabeth Museum cooperative tagging programs from 1984 to 2004. The adjusted estimate for juvenile survival was 0.56 and that for adult survival was 0.89. The adjusted estimate of probability of capture for juvenile sharks ranged from 0.06 to 0.17, while that for adult sharks was from 0.02 to 0.04. The mean annual abundance of juvenile sharks was 6800 (coefficient of variation, CV = 13%) and adult sharks 16 700 (CV = 9%). The accumulated effect of tag loss, nonreporting, and after release mortality were to reduce the overall estimate of juvenile and adult abundance by approximately 50%. The adjusted estimate of population size for both juvenile and adult sharks over the last decade appears to have remained constant (P > 0.05).

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