Browsing by Author "Cedras, Riaan Brinley"

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    The diet and feeding of the pelagic goby, sufflogobius bibarbatus, off Namibia
    (University of the Western Cape, 2009) Cedras, Riaan Brinley; Gibbons, M. J.; Faculty of Science
    The general diet of Sufflogobius bibarbatus in the northern Benguela upwelling ecosystem was investigated from gut content analysis in two separate studies. The first study was conducted over two 48 h diel sampling stations onboard the RV Dr. Fridtjof Nansen during a dedicated cruise conducted in January 2006, whilst the second was conducted on cruises of opportunity aboard the RV Welwitschia during 2001 and 2002. The results of both studies indicate that S. bibarbatus has a fairly generalised diet, feeding on benthic and pelagic animals for the most part: phytoplankton was uncommonly reported from the 3739 fish examined. Larger fish ate primarily benthic organisms, whereas smaller individuals include substantial number of pelagic organisms in their diet. There would appear to be a clear relationship between the environment occupied by individuals and their diet: large fish are predominantly demersal and display limited vertical migration, whilst small fish are thought to be more pelagic. Results strongly indicate that this species is opportunistic. The present study sheds new light on the ecology of the species, which is becoming increasingly important in the region.
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    Patterns in diversity, abundance, distribution and community structure of epi-pelagic copepods in the south-western Indian Ocean
    (University of the Western Cape, 2016) Cedras, Riaan Brinley; Gibbons, Mark J.
    The primary objective of this study was to investigate patterns in diversity, abundance, distribution and community structure of epi-pelagic copepods across the South West Indian Ocean Ridge (SWIOR). A survey was conducted across the SWIOR at two off-ridge and five seamount stations between 26.94 oS to 41.48 oS in November and December 2009. Copepod species richness and abundance was compared at vertical and horizontal scales day and night, at irregular time intervals across the Agulhas Return Current (ARC), Subtropical Front (STF) and Sub-Antarctic Front (SAF). A total of 49 genera and 135 epi-pelagic copepod species were identified along the SWIOR transect, and the Order Calanoida had the most genera. Species richness was highest in the ARC and lowest at the stations associated with the frontal areas of the STF and the SAF. The total number of copepod species was higher during the night than day. Total copepod abundance along the transect was highest towards the frontal area of the STF, and the genus Oithona spp. comprised almost 50% of the total number in all copepod samples. Three distinctive copepod assemblages were identified by multivariate analysis, and communities were associated with the STF, ARC and SAF. Clausocalanus laticeps, Metridia lucens and Calanus simillimus were only recorded in the southern part of the survey area and their absence in the north may demonstrate the strong stratification of the STF, and more likely to be the physiological properties, adaptation to their environment and life histories.