Land-use activities occurring in the upper catchment of the Olifants River System affect 

the water quality of Loskop Dam. Such activities lead to water pollution and that affect 

the health of fish and other aquatic organisms. The aim of the study was to determine 

the health status of Loskop Dam by assessing the health and parasites of Oreochromis 

mossambicus and Labeo rosae as biological indicators. The selected fish species were 

examined during summer (March) and winter (June) 2018. The Health Assessment 

Index (HAI), Condition Factor (K) of fish in conjunction with water quality analysis and 

the Inverted Parasite Index (IPI) was used to evaluate the ecological status of Loskop 

Dam. Fish were collected using gill nets varying in mesh sizes and fishing rods. Water 

quality parameters were measured during each survey and the morphometrics of each 

host specimen were taken. Fish was euthanised and all organs examined and giving 

scores using the HAI. All parasites were fixed and preserved using standard methods. 

The HAI (IPI) of O. mossambicus ranged was 44.6 during summer and 62.3 during 

winter. For L. rosae the score was 41.3 in summer and 48.46 during winter. The HAI 

and water quality results indicated that Loskop Dam is an intermediate impacted 

environment. Parasites; Cichlidogyrus spp., Dactylogyrus sp., Macrogyrodactylus spp.,

Neoergasilus japonicus, Contraceacum sp., Argulus japonicus, Acanthogyrus sp. and

digenean larvae were recorded. The highest mean intensity levels were recorded for 

Dactylogyrus sp. from the gills of fish. Number of parasites recorded from the study 

varied between seasons and the recorded mean intensities were not very high and did 

not affect the health of fish. This study represents new geographical records for the

parasites from the two host species.

TABLE OF CONTENTS

ABSTRACT .................................................................................................................................................. i

LIST OF TABLES...................................................................................................................................... iv

CHAPTER 1: GENERAL INTRODUCTION AND PURPOSE OF THE STUDY...............................1

1.1 Introduction.......................................................................................................................................1

1.2 Overview of the study area.........................................................................................................2

1.2.1 The Olifants River Catchment ................................................................................................2

1.2.2 Loskop Dam ........................................................................................................................2

1.3 Fish species......................................................................................................................................4

1.3.1 Oreochromis mossambicus..........................................................................................................4

1.3.2 Labeo rosae..................................................................................................................................5

1.4 Purpose of the study: problem statement, aims and objectives...............................................6

1.4.1 Problem statement......................................................................................................................6

1.4.2 Aim...............................................................................................................................................6

1.4.3 Objectives of the study ................................................................................................................7

CHAPTER 2: WATER QUALITY .............................................................................................................8

2.1 Introduction.......................................................................................................................................8

2.2 Methods and materials ...................................................................................................................9

2.2.1 Field work.....................................................................................................................................9

2.2.2 Laboratory work...........................................................................................................................9

2.3 Results and discussion.................................................................................................................11

2.3.1 Physico-chemical parameters....................................................................................................11

2.3.2 Inorganic non-metallic constituents..........................................................................................14

CHAPTER 3: FISH HEALTH ASSESMENT ........................................................................................17

3.1 Introduction.....................................................................................................................................17

3.2 Parasite Index ................................................................................................................................18

3.3 Condition factor (K) .......................................................................................................................19

3.4 Methods and material ...................................................................................................................19

3.4.1 Sampling of host specimens.......................................................................................................19

3.4.2 Examination and analysis of host fish........................................................................................19

3.4.3 Calculating the Health Assessment Index and Condition Factor...............................................20

3.5 Results and discussion.................................................................................................................21

3.5.1 Evaluation of the HAI .................................................................................................................21

3.5.1.1 HAI for O. mossambicus..........................................................................................................22

3.5.1.2 HAI for L. rosae........................................................................................................................22

3.5.2 Evaluation of the Condition factor (K) .......................................................................................25

CHAPTER 4: FISH PARASITES ...........................................................................................................26

4.1 Introduction.....................................................................................................................................26

4.2 Methods and materials .................................................................................................................26

4.2.1 Collection of parasites................................................................................................................26

4.2.2 Fixing and preservation of parasites..........................................................................................27

4.2.3 Laboratory work.........................................................................................................................27

4.2.4 Statistical analysis......................................................................................................................28

4.3 Results and discussion.................................................................................................................28

4.3.1 Ecto-parasites.............................................................................................................................30

4.3.2 Endo-parasites ...........................................................................................................................31

4.3.3 Infestation statistics of parasites...............................................................................................33

CHAPTER 5: GENERAL CONCLUSIONS ..........................................................................................34

CHAPTER 6: REFERENECES..............................................................................................................35

APPENDIX A.............................................................................................................................................41