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The diet of selected benthic feeding fish in the Mfolozi-Msunduzi system, KwaZulu-Natal

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dc.contributor.advisor Cyrus, D.P.
dc.contributor.advisor Vivier, L.
dc.contributor.author Nhleko, Jabulile Blessed Busisiwe
dc.date.accessioned 2012-08-16T07:48:25Z
dc.date.available 2012-08-16T07:48:25Z
dc.date.issued 2011
dc.identifier.uri http://hdl.handle.net/10530/1100
dc.description Submitted to the Faculty of Science and Agriculture in fulfillment of the requirements for the degree of Master of Science in the Department of Zoology at the University of Zululand, South Africa, 2011. en_US
dc.description.abstract The St Lucia estuarine system is considered to be the largest nursery area for estuarine-associated marine fish in southern Africa. The prolonged mouth closure due to regional droughts has resulted in large declines in its fish and prawn communities with deleterious consequences for regional marine populations, especially those that require estuaries for completion of their life cycle. Mouth closure of the St Lucia system contributed to a renewed interest in the St Lucia-Mfolozi System link, particularly the importance of the Mfolozi system in terms of its role as a refuge and alternative nursery area for species which cannot recruit into the closed St Lucia system when the Mfolozi remains open. The Mfolozi-Msunduzi estuarine system is the closest open estuary to St Lucia but there is a paucity of data on the ecological functioning of the system. Studies on the benthos of the Mfolozi-Msunduzi estuarine system have found it to be impoverished but large numbers of benthic feeding fish are present in the system at times. This raised the question: if the zoobenthic community is impoverished and high numbers of benthic feeding fish are nevertheless present in the system, then what are these fish feeding on? The stomach contents of 961 fish of 15 different species collected between August 2008 and March 2010 using seine and gill nets were examined. Of these 15 species, only six were caught in sufficient numbers for gut analysis. The six species that were used in the analysis were Leiognathus equula, Acanthopagrus berda, Glossogobius giurus, Ambassis ambassis, Ambassis gymnocephalus and Ambassis natalensis. Four methods were used for stomach content analysis, namely Frequency of occurrence, Numerical occurrence, Points (Proportional Volumetric) analysis and Index of Relative Importance (IRI). It was found that the diet of L. equula was dominated by the copepod, P. stuhlmanni, with the macrobenthos contributing <0.5% to the overall diet of the species. Similarly, the diet of A. berda was dominated by P. stuhlmanni, with the benthic fauna contributing <1.5% to the diet. The dominant prey in the diet of G. giurus was Glossogobius sp, while the only benthic species that was fed on was the crab P. blephariskios, which contributed not more than 0.3% to the overall diet of the species. A large proportion of the Ambassids (A. ambassis, A. gymnocephalus and A. natalensis) had empty stomachs, whilst most of those that contained food had stomachs < 30% full, based on the Points determination method. The diet of all three Ambassid species was dominated by P. stuhlmanni, with A. gymnocephalus feeding only on the copepod. The total contribution of the benthic fauna found in the diet of A. ambassis was <30% and <1% in A. natalensis. Copepods dominated the diets of the majority of the species examined, indicating that in the Mfolozi system, zooplankton rather than benthic organisms are being fed on. This tends to tie in with the impoverished state of the benthic fauna. The results of this study indicate that only those species capable of adapting their diets to whatever is available and abundant to feed on will be able to survive in the Mfolozi-Msunduzi system. en_US
dc.description.sponsorship National Research Foundation (NRF), the University of Zululand Research Committee and the Department of Environmental Affairs. en_US
dc.language.iso en en_US
dc.publisher University of Zululand en_US
dc.subject Estuaries -- South Africa -- KwaZulu-Natal en_US
dc.subject Estuaries--South Africa--St Lucia estuary en_US
dc.subject Benthic feeding fish en_US
dc.title The diet of selected benthic feeding fish in the Mfolozi-Msunduzi system, KwaZulu-Natal en_US
dc.type Thesis en_US

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