..................................................................................................................................... 5 List of Figures ............................................................................................................................ 6 List of Tables ............................................................................................................................. 8 Introduction ................................................................................................................................ 9 The Benguela Ecosystem ....................................................................................................... 9 Horse mackerel in the Benguela .......................................................................................... 10 Population structure of Trachurus trecae and Trachurus capensis ..................................... 13 Parasites as biotags .............................................................................................................. 14 Materials and Methods ............................................................................................................. 17 Study site .............................................................................................................................. 17 Sample collection and processing ........................................................................................ 18 Data analysis ........................................................................................................................ 20 Results ...................................................................................................................................... 21 Parasite assemblages ............................................................................................................ 22 Statistical analyses ............................................................................................................... 26 Size effect of parasite assemblages between small and large Trachurus trecae ............. 26 Sex effect of parasite assemblages of Trachurus trecae .................................................. 26 Interspecific differences of parasite assemblages of Trachurus trecae and Trachurus capensis ............................................................................................................................ 27 Selected Parasite species ...................................................................................................... 27 Discriminate Function Analysis (DFA) ........................................................................... 32 Discriminate analysis of Small and large Trachurus trecae ............................................ 32 Discriminate analysis of Trachurus trecae and Trachurus capensis ............................... 33 Discussion ................................................................................................................................ 35 Intraspecific comparisons .................................................................................................... 36 Un iv rsi ty of Ca pe To wn