published_or_final_version / abstract / Zoology / Doctoral / Doctor of Philosophy

published_or_final_version / Biological Sciences / Doctoral / Doctor of Philosophy

published_or_final_version / Biological Sciences / Doctoral / Doctor of Philosophy

M.Sc. / Please refer to full text to view abstract

by Choy Ka-Fai. / Thesis (M.Phil.)--Chinese University of Hong Kong, 2000. / Includes bibliographical references (leaves 107-125). / Abstracts in English and Chinese. / ACKNOWLEDGEMENTS --- p.I / 論文摘要 --- p.II / ABSTRACT --- p.III / ABBREVIATIONS --- p.V / TABLE OF CONTENTS --- p.VI / Chapter CHAPTER 1 --- INTRODUCTION --- p.1 / Chapter CHAPTER 2 --- PURIFICATION OF GRASS CARP ALDH FROM MITOCHONDRIA --- p.18 / Chapter CHAPTER 3 --- PURIFICATION & CHARACTERIZATION OF GRASS CARP ALDH --- p.49 / Chapter CHAPTER 4 --- CONCLUSION --- p.104 / REFERENCES --- p.107

Thesis (Ph. D.)--University of Hong Kong, 2007. / Title proper from title frame. Also available in printed format.

In this thesis, the efficiency of orally applied praziquantel (PQ) in two concentrations (Pramik 1 and Pramik 2) and mebendazole (MB) were tested on metacercaria of eye flukes (Diplostomum spathaceum, Rudolphi, 1819) in the grass carp (Ctenopharyngodon idella, Valenciennes, 1844). Naturally infected fish (average fish weight was 1.6 g and standard deviation was 0.1) were divided into four groups, for each tested group (Pramik 1, Pramik 2 and MB) belonged two aquariums of 100 liters each with 25 fish and for a control group belonged three aquariums of 100 liters each with 25 fish. The fish in the individual groups were fed with medicated feed containing praziquantel (Pramik 1 - 2.5 g PQ. kg-1 of feed, Pramik 2 - 1.25 g PQ. kg-1 of feed) and medicated feed mixture KP1 enriched with mebendazole (2.5 g MB. kg-1 of feed). The control group was fed with KP1 without drug addition. During the test the parasitological examinations of the ophthalmic lens were performed. The prevalence and intensity of infection were recorded. In the group of fish fed with medicated mixture containing MB, no statistically significant differences of the intensity of the infection indicating the MB potential in the fight against this fish infection were reported during the test. In the case of tested groups of fish fed with medicated feed mixture containing PQ (Pramik 1, Pramik 2), a statistically significant difference in the intensity of the infection was proved compared with the control group already after the first examination (estimated dose of consumed PQ. kg-1 of weight of fish = 500 and 250 mg). Near complete elimination of the eye flukes occurred in the group fed with feed mixture Pramik 1 after the expected consumption of 900 mg PQ. kg-1 of weight of fish. Statistically significant differences in the intensity of the infection in PQ treated fish groups compared to control groups indicate the usability of medicated feed containing PQ in the fight against fish diplostomosis.

Ph.D. (Zoology) / Please refer to full text to view abstract

M.Sc. (Zoology) / Ari investigation was made into the biological control of the submerged aquatic weeds Potamogeton pectinatus, Lagarosiphon major and L. muscoides in the Florida Lake, Transvaal using the Chinese grass carp Ctenopharyngodon idella (Val.) as biological control agent. The physical, chemical (including selected heavy metals), faunal and bacteriological conditions were also investigated over a period of one year. The total standing crop of P.pectinatusand Lagarosiphon spp, were reduced from an initial 0,193 kg m" 2 (wet mass) in March 1990 to 0,0338kg m-2 (wet mass) in March 1991. Reductions in the densities of the macrophytes coincided with a corresponding increase in chIorophyll-a values in the water columm of the lake. Abnormally high concentrations of the heavy metals copper, manganese, iron, nickel chromium, zinc and lead were found to occur in the lake sediments, aquatic macrophytes, ftlamentous algae, macroinvertebrate fauna as well as in organs and tissues of the perch Perea fluviatilis. These metals could be related to gold mining activities which occurred in the vicinity of the lake some years ago. Faecal bacterial counts of the water in the lake point towards the possible contamination of the lake water with domestic sewage. Ari analysis of the faeces of the numerically dominant birds which occur at the lake i.e. the coot Fulica aistata and the egyptian goose Alopochen aegyptiacus suggest that the main cause of faecal contamination of the lake's water possibly originates from these and other water birds frequenting the lake. By using the results on the physical-chemical conditions in the lake, conditions which presently prevail can be summarized as being largely that of a mesotrophic impoundment with strong tendencies towards eutrophic conditions. Secondary effects of the grass carp on the lake ecosystem was the progressive decline of weed eating birds and a slight increase in the numbers of piscivorous birds, both of which could be linked to the drastic reduction in the standing crop of the submerged weeds in the Lake. The present survey confirms the value of the Chinese grass carp as biological control agent in the management of excessive growths of submerged aquatic weeds in lakes and reservoirs in South Africa...

A study of Asian clam (Corbicula fluminea Müller) colonization in relation to changes in aquatic vegetation community as a result of management of Hydrilla verticillata (L. f.) Royle with grass carp was conducted at the Lewisville Aquatic Ecosystem Research Facility (LAERF), Lewisville, TX, from April 2015 through October 2016. Percent vegetation cover, C. fluminea abundance and water quality metrics (pH, turbidity, conductivity, DO, calcium, chlorophyll a) from 16 experimental subjects were analyzed. Treatments included four replicated grass carp stocking densities; 1-control with no fish stocked (n = 4), 2-low density of 40-43 fish per vegetated ha (n = 4), 3-medium density of 72-81 fish per vegetated ha (n = 4) and 4-high density of 110-129 fish per vegetated ha (n = 4). Data analysis showed statistical significance in the relation of C. fluminea abundance to percent vegetation cover (multiple linear regression, r2 = 0.820), grass carp stocking densities (two-way analysis of variance, p = <0.001) and chlorophyll a (multiple linear regression, r2 = 0.339). Findings of this research indicate the possibility that management of hydrilla had enabled establishment of secondary invasive species.