Thesis (M.Sc.-Res.)--University of Wollongong, 2007. / Typescript. Includes bibliographical references: p. 69-83.

Thesis (M.Sc. (Ichthyology & Fisheries Science)) - Rhodes University, 2008.

Thesis (M.S.)--University of North Carolina Wilmington, 2009. / Title from PDF title page (February 22, 2010) Includes bibliographical references (p. 105-109)

Thesis (Ph. D.)--Simon Fraser University, 2001. / Includes bibliographical references.

Thesis (Ph.D.) -- Mississippi State University. Department of Biological Sciences. / Title from title screen. Includes bibliographical references.

M.Sc. / This study aims to assess the potential impacts of coal mine activity on exposed fish assemblages in the Mpumalanga Highveld area. A control-impact-assessment method was applied, with sites located upstream and downstream from mining activity. All sites were located in the upper Olifants catchment. Field assessments were done over a high flow and low flow period. It was ascertained that water quality variables contributing towards differences between upstream and downstream environmental conditions are salt concentrations, pH and oxygen saturation. Alterations on fish community structures indicated a categorical decline in abundances and species richness at sites situated downstream from mining activity, while Fish Response Assessment Index (FRAI) scores similarly reflected more impaired fish assemblages at downstream sites. Redundancy analysis (RDA), using fish assemblages and FRAI driver metrics explained 36.5 % of variance obtained and reflected particular alteration in Barbus neefi, B. paludinosus, Tilapia sparrmanii and Pseudocrenilabrus philander populations. Sites most severely impacted were identified, as well as the main drivers responsible for changes in fish assemblages. The Cover metric contributed significantly (p<0.05 to variance measured. Subsequent community threshold management targets are presented for problem sites, which aim to manage each site at an ecological category one class higher than the Present Ecological State (PES).

The biogeography and community structure of the fishes of South African estuaries was investigated. In all, 109 systems were examined representing two broad types: temporarily closed and permanently open estuaries. Multivariate analyses of the fish communities identified three biogeographic regions. A cool-temperate region extended along the west and southwest coasts; a warmtemperate zone stretched along the south, southeast and east coasts and a subtropical region occurred along the east coast. The boundaries of these biogeographic regions were also delineated. The general physico-chemical characteristics of the estuaries within the three biogeographic regions also reflected regional differences in climate, rainfall and ocean conditions. Estuarine temperatures followed the trend for marine coastal waters, decreasing from subtropical estuaries toward cool-temperate systems. The low rainfall and runoff in the warm-temperate region together with high evaporation rates and strong seawater input resulted in higher salinities in these estuaries. These factors also accounted for the predominantly clearer waters in warm-temperate estuaries. The estuaries in the three biogeographic regions were also shown to contain somewhat distinctive fish assemblages. Temperature and salinity appeared to be the two main factors affecting the distribution and abundance of fishes in South African estuaries. Subtropical systems were characterised by fishes mostly of tropical origin as well as certain south coast endemic species. Warm-temperate estuaries were dominated by endemic taxa with some tropical species also present. The fish fauna of cooltemperate estuaries mostly comprised south coast endemic species with cosmopolitan and temperate taxa also present. Certain functional components of the ichthyofauna also exhibited slight differences between regions. Freshwater fishes were a major component of closed subtropical estuaries while estuarine resident species were more abundant in warm-temperate estuaries. Overall, estuarine-dependent marine species dominated the fish fauna of the estuaries in all biogeographic regions, signifying that South African estuaries perform a vital nursery function for this group of fishes. Slight differences were also apparent in the trophic structure of the fishes; these were related to environmental differences between regions. Zooplanktivores and fishes that feed on aquatic macrophytes/invertebrates assumed a relatively higher importance in warm-temperate systems. Overall, detritivores dominated the estuarine fish fauna in all regions, indicating that detritus forms the main energy source in South African estuaries.

Within temperate coastal seascapes, macroalgae provide habitats for different organisms such as invertebrates and fish. In analogy to seagrass meadows, macroalgae beds are known for their importance as fish nurseries. However, within the Baltic Sea the importance of the canopy forming macroalgae Fucus vesiculosus for coastal fish communities, especially the juveniles, is unclear. In order to address this knowledge gap, fish communities in areas with and without F. vesiculosus were investigated around Askö, an island in the archipelago of the Baltic Sea. Sites were subjected to different exposures (sheltered, exposed or very exposed) and three different methods were used for sampling (underwater visual census (UVCs), beach seine netting and remote underwater videos (RUVs)). Overall, fish community composition differed significantly among locations and fish abundance and fish biomass were significantly higher in sites with F. vesiculosus than sites without. There was no significant relationship between algae cover or habitat complexity and fish abundance/biomass in sites with F. vesiculosus. Fish behaviour differed between sites with and without F. vesiculosus, with fish feeding more in sites with F. vesiculosus and traveling more in sites without F. vesiculosus. Only one location, Knabberskär, had significantly higher species richness in F. vesiculosus than in sites without F. vesiculosus. There were no differences in juvenile abundance among sites with or without F. vesiculosus and abundance of adult fish was higher than juvenile fish, regardless of location, site or species. Mean invertebrate abundance was a twice as high in the sheltered location Husbåtsviken than in Knabberskär. Higher fish abundance, fish biomass and species richness in sites with F. vesiculosus compared to sites without, suggest that macroalgae may play an important role in the Baltic Sea, however it might not be as important for juvenile fishes as predicted. The three different sampling methods provided similar results for fish abundance, but not for fish biomass. Continued studies where the relationship between fish communities and aspects of F. vesiculosus structure (such as canopy height) as well as linkage with other habitats is recommended for further understanding and better protection of F. vesiculosus habitats.

Seagrass habitats are critical habitat for many fish species and are currently threatened by anthropogenic and natural factors, such as coastal development, pollution, global climate change, and sea level rise. There are few studies that have tracked long- term changes in seagrass habitat and their associated fish communities. This project addressed this need using data collected by the United States Geological Survey (USGS) from two South Florida sites, North Biscayne Bay, FL (NBB) and Port of Miami, FL (POM). The USGS sampling was part of ongoing monitoring projects designed to assist future management decisions that would enhance the protection of these valuable habitats. Data were collected biannually at the conclusion of the dry (April) and wet (September) seasons from 30 cells at each site. In each cell, the data collected included: six replicates for seagrass species and cover, five sweep net collections for fish species and abundance, as well as abiotic variables (water temperature, salinity, turbidity, water depth, and sediment depth). A distinct loss in fish and seagrass species were observed, particularly between the years of 2011-2014. These years coincided with several events including: the Port Miami Deep Dredge (PMDD) project during the years 2013-2015; periods of drought; and major storm events. Changes in fish community structure over this time period were largely driven by loss of species and increased homogenization of fish communities at both locations. More specifically, the NBB community shifted to resemble that of POM by 2014. These changes mirrored the loss of seagrass cover at both locations. Further studies are required to assess the extent to which ongoing dredging activities and other factors might be affecting seagrass cover, which ultimately affect fish communities.

Most northeastern river basins are stressed by the effects of development but the complexity of evaluating rivers often hinders the establishment of effective management regulations. Many methodologies have been proposed for assessing instream habitat, determining critical flow levels, and evaluating biological communities, but no one approach is universal. The overall objective of this thesis is to move towards standardizing components of river modeling. Rather than examine a full model, I investigated individual steps of MesoHABSIM, an instream habitat modeling approach. The two components studied involved applying the Reference Fish Community (RFC) method to identify a biological reference; and using depth and velocity data to standardize the description of hydraulic types. The RFC approach identifies the fish species and the expected proportions that should be present in a less impacted version of a river system. The Eightmile River watershed, was the focus of the study in which the RFC approach was employed to determine whether the fish community of this rural watershed, meets or exceeds a community developed using reference rivers. Similarity indices were used to identify differences between the existing (field-sampled) and expected communities. While the analysis of the Eightmile community indicates that it is in a better condition than the majority of rivers studied, it also shows some deviation from the reference, most likely due to elevated water temperatures and regional declines. The hydraulic type characterization study was developed to reduce the effort needed in depth and velocity measurement after this was identified as the most time consuming portion of the MesoHABSIM methodology. I used a series of pair-wise, independent-sample, Kolmogorov-Smirnov tests on a large bank of depth and velocity data to determine if patterns could be confirmed for each type of hydromorphological unit (HMU) across various streamflows. Few of the data sets were statistically similar enough to be combined and the mapping effort could not be simplified based on this investigation. Neither investigation provided the intended reference for the particular component of river modeling, further emphasizing the complexity in this area of study. However, the information gathered can be used as pioneering steps in future investigations.