The studies on the Vaal River and its tributaries presented here, were carried out for a variety of reasons. Prominent among them were several of immediate practical importance, such as the need to know the pollution status of waters which ultimately form the major supply for the Witwatersrand urban and industrial complex, and the need for background data on a stretch of the river which was to be insecticided to control a Simulium pest. However the results of such work can often be used for wider purposes. In this thesis they are used to examine the major factors thought to govern the distribution and abundance of the invertebrate Metazoa in the river. Introduction, p. 2-3.

A comparative, limnological study of five, small, eutrophic lakes in the Interior of British Columbia was made over a period of two summers. Detailed morphometrical, physical, chemical and biological data are given. The effect of a rotenone base compound on the fauna of two of these lakes is shown both qualitatively and quantitatively by comparing them with the faunas in other lakes. A complete eradication of the fish in the lakes was obtained. Certain species of plankton and bottom organisms were killed by the poison but sufficient numbers survived to re-populate the lakes. The plankton populations did not revert to the previous level of abundance in the year following. The effect of the absence of coarse fish on certain shore organisms and Gladocera was indicated. / Science, Faculty of / Zoology, Department of / Graduate

The species composition, primary productivity and relative abundance of the plankton organisms in Marion Lake, British Columbia were recorded at biweekly intervals for two months following artificial enrichment with nitrate or phosphate or both, of six large wooden enclosures within the lake in four seasons during the year. Enrichment resulted initially in a decrease in diversity and an increase in the productivity of the phytoplankton and standing crop of the entire plankton community. These events were collectively termed a "regressive succession" because their "direction" of change was the reverse of that normally encountered in primary and secondary successions. The regressive succession terminated following algal bloom formation, and diversity began to increase slowly while the primary productivity and standing crop of the plankton dropped. This was indicative of the beginning of a secondary succession in which one group of dominant species was replaced by another and then others in turn replaced these. This successional pattern occurred regardless of season, prevailing physical, chemical, or climatological factors. Thus, such a pattern appeared to be a very general one and was disrupted only by the physical removal of the majority of the planktonic species from the lake resulting from persistent and heavy rains which "flushed" the lake. A statistical analysis of each of the 167 euplankton species observed in the lake was performed using the data from each of the four enrichment series to determine which species responded significantly to artificial enrichment. The individual response patterns were nearly as diverse as the species themselves, however, one of the most common responses was made by very rare species which "bloomed" two to three weeks after nutrient addition. Few primary producers responded to more than one type of nutrient enrichment in any one season which emphasized the importance of Liebig’s Law of the Minimum. The higher trophic levels, on the other hand, responded more to the increase in standing crop in the different enclosures than to any one particular type of nutrient enrichment. The Shannon-Weaver formula, H =nP, log P, was modified by changing the definition of Pi, that is, the individuals in the ith species divided by the total number in the sample. This index was insensitive to changes in the relative abundance of the planktonic species from the higher trophic levels. Pi was redefined so that it was less sensitive to number and more sensitive to both relative biomass and relative productivity. This new index of diversity (Hp ) did not act selectively on the different trophic levels represented in the plankton samples. An understanding of the principles governing community organization and biotic succession should be based on the life history of the individual species comprising the community and not on assumptions about supposed trophic changes. This study indicated that pertinent information about the changes in the structure of a planktonic community could be gained from an analysis of the changes in the relative abundance of each of the species without artificially isolating and culturing these species and without lumping all the organisms into vague trophic categories. / Science, Faculty of / Zoology, Department of / Graduate

The density of the animals forming the bottom fauna of Paul Lake, British Columbia has been estimated for two successive seasons, based on 250 Ekman dredge samples from all zones for each year. After the sampling of the first year, the lake was treated with .004 p.p.m. Toxaphene. Density changes in the invertebrate population were considered on the basis of increase, decrease and changes in zonal distribution. Following poisoning and elimination of predatory fish, density increases occurred in the Physidae, Lymnae-idae, Oligochaeta, Planoribae, and Hirudinea. Density decreases occurred in the Watermites, Amphipods, Chiron-omidae, Planaria, Sphaeriidae and Odonata. Tricoptera, Ephemeroptera and Ceratopogonidae were not taken in any of the samples after poisoning. / Science, Faculty of / Zoology, Department of / Graduate

No description available.

Thesis (M.Sc. (Hons.)) -- University of Western Sydney, 2000. / "A thesis submitted in part-fulfilment of the requirements for the degree of Master of Science (Honours)" Bibliography : leaves 131-152.

Freshwater vertebrates were sampled in different waters of the Upper Parramatta River catchment to determine their patterns of distribution with respect to water quality. A total of 730 animals (831 captures)were caught between November 1997 and December 1998. Data was collected on three freshwater turtle species, and four fish species.The abundance of aquatic vertebrates was correlated with physiochemical water quality parameters. The large aquatic vertebrates studied did not correlate with the commonly used parameters for aquatic health. The assumption ANZEEC water quality parameters are the definitive determinant of aquatic health for vertebrates is, therefore, erroneous. / Master of Science (Hons)

Inaug.-diss.--Basel. / Curriculum vitae. "Literaturverzeichnis": p. [154]-163.

Data taken from the literature were used to develop and evaluate models predicting fish biomass and yield, crustacean zooplankton biomass, and profundal macrobenthos biomass in lakes. Total phosphorus concentration and macrobenthos biomass/mean depth were the best univariate predictors of fish biomass and yield. Phosphorus concentration was also the best predictor of zooplankton and macrobenthos biomass. In experiments testing for inter- and intraspecific competition, conducted in situ at densities based on measured natural fish densities, growth of yellow perch (Perca flavescens) and pumpkinseed (Lepomis gibbosus) reared alone was inversely related to density. Both species primarily ate macroinvertebrates when reared alone. When reared together: perch growth was significantly depressed compared to that of perch reared alone; pumpkinseed growth was equivalent to that of pumpkinseed reared alone; and the diet of perch changed to include food of inferior quality (microcrustaceans) in the presence of the superior competitor, pumpkinseed, whose diet did not change.

Inaug.-diss.--Basel. / Curriculum vitae. "Literaturverzeichnis": p. [154]-163.