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Ecological Parameters of Selected Helminth

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Ecological Parameters of Selected Helminth ECOLOGICAL PARAMETERS OF SELECTED HELMINTH SPECIES IN LABEOBARBUS AENEUS AND LABEOBARBUS KIMBERLEYENSIS IN THE VAAL DAM, AND AN EVALUATION OF THEIR INFLUENCE ON INDICATORS OF ENVIRONMENTAL HEALTH By ALESSANDRA BERTASSO SHORT DISSERTATION submitted in partial fulfilment of the requirements for the degree MASTER OF SCIENCE in ENVIRONMENTAL MANAGEMENT in the FACULTY OF SCIENCE at the RAND AFRIKAANS UNIVERSITY SUPERVISOR: PROF. A. AVENANT-OLDEWAGE MAY 2004 ACKNOWLEDGEMENTS My sincere thanks and gratitude go to: ∗ My partner in life and love, Dwayne, for all his support, love and continual motivation. ∗ My supervisor, Professor A. Avenant-Oldewage, for her support and patience throughout my study. ∗ Rand Water for making water quality data available. ∗ Rand Afrikaans University for financial support. ∗ Zoology Department at RAU for use of facilities. ∗ The staff and students at the Zoology Department for assistance in field work. ∗ Groot Eiland staff for their help and use of facilities. ∗ S.N. Mashego for his assistance in identifying the tapeworms collected. ∗ Riette Eiselen from RAU Statkon for statistical analyses of my data. ∗ My colleague and friend, Bronwyn Gernet for assisting with the maps. ∗ My Parents, for giving me the opportunity to further my studies and for their unconditional love and support. ABSTRACT Surveys conducted by the Rand Afrikaans University fish parasitology group have shown unexpectedly high numbers of helminth parasites (endoparasites) in yellowfish species in the Vaal Dam. The high number of helminth parasites can be attributed to a cestode species (Bothriocephalus spp.) which has been introduced with cyprinid fish into South Africa from Asia. It was expected that this opportunistic introduced species, in its high numbers, may affect the accuracy of the fish health assessment index (HAI). The main purpose of this research project was to determine the infection (in terms of prevalence, mean intensity and abundance) of the helminth species found in yellowfish in the Vaal Dam and determine whether it plays a role in calculating the health status of the fish as expressed in the Health assessment Index (HAI) and thus have an impact on the value obtained for the quality of the environment they live in. Seasonal surveys were conducted at the Vaal Dam between April 2000 and January 2001. Twenty smallmouth yellowfish (Labeobarbus aeneus) and 20 largemouth yellowfish (Labeobarbus kimberleyensis) were collected with the aid of gill nets and used as indicator fish species. The two yellowfish species sampled were identified based by the distinctive size of their mouths. Fish were examined for external parasites after which they were weighed and measured. Blood was drawn and slime smears were made. Blood and slime smears were examined with a compound microscope for the presence of parasites. Fish were killed, dissected and then examined as prescribed in the fish HAI. Internal parasite numbers were recorded. Helminth parasites were extracted from the intestines of infected fish and examined. The cestodes were identified as either Bothriocephalus acheilognathi Yamaguti, 1934 based on the heart-shaped scolex and presence of bothria or “other cestode spp.”. The majority (99.8%) of the cestodes found for both yellowfish species were identified as B. acheilognathi. The prevalence, mean intensity and abundance of B. acheilognathi (Asian tapeworm) in both yellowfish species were calculated. Ecological parameters including species specificity, seasonality, gender specificity and relationships between fish size and the Asian tapeworm prevalence were also included. From the endo- and ectoparasite data collected, infestation statistics and ecological parameters (species specificity, seasonality and gender specificity) were calculated. Two HAI values were calculated for each fish species; one including all parasites found and the second excluding the number of B. acheilognathi found. To verify the results of the HAI, water quality, made available by Rand Water, was included in the study. The Vaal Dam, located in the upper reaches of the Vaal River, is believed to have reasonably good water quality. This theory was supported in this study; water quality in the Vaal Dam during the four surveys was relatively good with high turbidity, high dissolved oxygen and low TDS characteristics. In this study B. acheilognathi preferred Lb. kimberleyensis over Lb. aeneus although a low infection rate was observed in smallmouth yellowfish. Furthermore the infection (in terms of prevalence, abundance and mean intensity) in largemouth yellowfish was markedly high. Seasonal patterns observed in the Asian tapeworm’s infection of smallmouth yellowfish were attributed to breeding and subsequent feeding patterns of this fish species with relatively high infections recorded in winter and spring. For Lb. kimberleyensis no explanation could be given regarding the seasonal patterns observed for the mean intensity and abundance of B. acheilognathi. The maximum and minimum mean intensity and abundance values in largemouth yellowfish were recorded in autumn and spring respectively. In addition the prevalence of B. acheilognathi was high throughout the four surveys. Regression analysis indicated that the presence/absence of B. acheilognathi most successfully predicted (80.6%) the fish as belonging to the correct fish species. In terms of the HAI, higher values were calculated for Lb. kimberleyensis than Lb. aeneus when including the number of Asian tapeworms in the HAI calculations. When excluding the number of Asian tapeworms from the HAI calculations, slightly higher but similar values were obtained for both fish species. Seasonal changes in water quality in the Vaal Dam were not reflected in the Asian tapeworm’s infection or the HAI. Therefore B. acheilognathi and its high infection in Lb. kimberleyensis, directly influences the high health index value obtained for this fish species. However it does not reflect a poorer water quality as would be expected when observing higher HAI values. Statistical analyses indicate that if the HAI excluding the number of B. acheilognathi is a good indication of fish health then the HAI including all parasites would also be a good indication of fish health except the HAI values would be 1.03 times higher. OPSOMMING Opnames wat uitgevoer is deur die visparasitologiese groep by die Randse Afrikaanse Universiteit het onverwagte hoë getalle helmint parasiete (endoparasiete) in geelvisspesies in die Vaaldam gevind. Die hoë getalle helminte kan toegeskryf word aan die voorkoms van ‘n lintwurm (Bothriocephalus sp) oorspronklik ingevoer saam met verteenwoordigers van die Cyprinidae uit Asië. Daar was verwag dat die hoë getalle van hierdie oppertunistiese ingevoerde spesie en die akkuraatheid van die Visgesondheidsindeks sal beïnvloed. Die hoofdoel van die navorsingsprojek was om die infeksie (in terme van persentasiebesmetting, gemiddelde besmettingsintensiteit en besmettingsmoontlikheid) van die helmintspesies in geelvisse in die Vaaldam te bepaal en vas te stel of dit ‘n effek het op die berekening van die gesondheidstatus van die visse soos uitgedruk in die Visgesondheidsindeks (VGI) en dus ‘n rol speel by waarde wat verkry word vir die omgewing waarin hulle leef. Seisoenlikse opnames is uitgevoer in die Vaaldam tussen April 2000 en Januarie 2001. Twintig kleinbekgeelvisse (Labeobarbus aeneus) en 20 grootbekgeelvisse (Labeobarbus kimberleyensis) is versamel met behulp van kieuenette en aangewend as indikatorspesies. Die twee geelvisspesies is geïdentifiseer op grond van die grootte van hulle bekke. Visse is deurgesoek vir die teenwoordigheid van uitwendige parasiete en daarna geweeg en gemeet. Bloed is onttrek en ‘n slymsmere is gemaak. Bloed en slymsmere is met behulp van ‘n saamgestelde mikroskoop vir die teenwoordigheid van parasiete ondersoek. Vis is gedood, gedissekteer en ondersoek soos voorgeskryf in die VGI. Inwendige parasiete se getalle is aangeteken. Helmintparasiete is verwyder uit die intestinum van besmette visseen bestudeer. Die cestode is geïdentifiseer as òf Bothriocephalus acheilognathi Yamaguti, 1934 gebasser op die hartvormige skoleks en aanwesigheid van bothria òf “’n ander cestood spesie”. Die meerderheid (99.8%) van die cestode wat in beide geelvisspesies voorgekom het, is geïdentifiseer as B. acheilognathi. Die persentasiebesmetting, gemiddelde besmettingsintensiteit en besmettingsmoontlikheid van B. acheilognathi (Asiese lintwurm) in beide geelvisspesies is bereken. Ekologiese parameters soos spesiespesifisiteit, seisoenaliteit, geslagsvoorkeur en die verband tussen visgrootte en die voorkoms van die lintwurm is ingesluit. Uit die endo- en ektoparasietdata wat versamel is, is infestasiestatistiek bereken. Twee waardes is bereken vir die VGI; een waar alle parasiete se voorkoms ingesluit is en een waar die getalle verkry vir B. acheilognathi uitgesluit is. Ten einde die waardes verkry vir die VGI te verifieer is waterkwaliteitsdata, wat van Randwater verkry is, ingesluit in die studie. Daar word geglo dat die Vaaldam wat in die bolope van die Vaalrivier geleë is oor redelike goeie waterkwaliteit beskik. Hierdie teorie word ondersteun in die studie; waterkwaliteit in die Vaaldam gedurende die vier opnames was relatief goed met hoë waardes vir turbiditeit, hoë opgeloste suurstof en lae totale opgeloste soliede partikels. In die studie het B. acheilognathi Lb. kimberleyensis verkies bo Lb. aeneus en ‘n lae infeksiekoers is waargeneem by kleinbekgeelvis. Voorts was die besmetting (in terme van persentasiebesmetting,
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