Coral reefs are priority habitats which are vulnerable to natural and anthropogenic disturbances. These can cause phase shifts from coral habitat to degraded algal-dominated states – and consequent changes in the distribution, abundance and activity of associated fish species. In the eastern Red Sea, human-induced reef degradation is likely to increase with planned development of the Saudi Arabian coast and the changing climate. The present study therefore investigates the ecological effects of coral-algal phase shifts in reef-associated fish communities, using naturally occurring within-reef benthic zones as proxies for levels of habitat health - with a focus on how these responses differ temporally. These zones were dominated by: hard coral (coral zone), coral and turf algae (transition zone), and macroalgal canopies (algal zone). Six inshore reef areas, were studied in periods with low and high densities of Sargassum in the algal zones (May and November respectively). Community composition was assessed via visual census and predation activity predicted using two proxies: in situ experiments and biomass of carnivores. In both periods, we observed distinct fish communities in each zone - with reduced species richness, Shannon-Wiener diversity and predation intensity, from the coral to the algal zones. Decreases in the abundance and biomass of fish also occurred from the coral to algal zones in May but a spike, as well as a shift in community composition, occurred in the algal zone in November. This shift is attributed to the vast increases in grazer biomass, predominantly Siganus luridus, associated with the November bloom of Sargassum canopies. The present study established, the composition and functioning of Red Sea fish communities is spatially and temporally affected by increased macroalgal dominance. This finding supports the need for herbivorous fish to be made a conservation priority in the management and conservation of reef systems in order to prevent phase shifts to algal dominated states. We conclude that if Red Sea reefs are allowed to shift to alternate states, depending on the density of macroalgal canopies, reefs may support high biomass and abundance of fish but the functioning of the fish community will be altered and the diversity lost.

The local substrate composition of large rivers varies with local current velocity and high flow events. We evaluated effects of hydrology on local substrate variation for 28 Wabash River sites from 2005-08, and subsequent variation in fish assemblages using multivariate analyses. Sites were 500-m in length and fish were collected by boat electrofisher. Substrate collection methods were compared by way of habitat pole, developed by Ohio River Valley Sanitation Commission (ORSANCO), and substrate grabs. We characterized hydrologic variation with the Indicators of Hydrologic Alteration (IHA) software. We determined important driving variables of fish assemblages, substrates, and hydrology with Principle Components Analysis. Temporal effects of hydrology and substrate variation on taxonomic and functional fish assemblages were determined by repeated measures ANOVA. The analyses resulted in annual variation in fish assemblage structure, substrates and hydrologic variation. Significant relationships were found for fish assemblage structure, substrate variation, and hydrologic variation. . Our Mantel tests resulted in significant concordance among hydrology, local substrate variation, and fish assemblage structure variables in years 2005, 2006, and 2008, but not in 2007. These results demonstrated that Wabash River fish assemblages respond to substrate variation and substrate variation is controlled largely by hydrology. A comparison of substrate quantification approaches demonstrated that the habitat pole and substrate grabs are both effective ways to describe fish assemblages but the costs of grabs outweigh the cost of the pole method. / Department of Biology

Thesis (Ph. D.)--Oregon State University, 2008. / Printout. Includes bibliographical references (leaves 208-223). Also available on the World Wide Web.

published_or_final_version / Ecology and Biodiversity / Doctoral / Doctor of Philosophy

Thesis (M.Sc. (Physiology)) --University of Limpopo, 2015 / Water is an essential and yet scarce resource, which has a vital role for human use and also serve as a habitat for numerous organisms in aquatic environments. Despite its scarcity there have been many reports indicating that it is continually polluted by domestic, agricultural, mining and other anthropogenic activities; subsequently affecting the health of organisms residing in such water bodies. Fish have been selected as the bio-monitoring species due to its direct interaction with the environment; thereby making it an appropriate model to monitor and evaluate the health status of the environment. The feral population of the alien species, Hypopthalmichtys molitrix (Valenciennes, 1844) commonly known as the silver carp in Flag Boshielo Dam has been considered a healthy population. However, this perception changed considerably after reports of lethargic, dying fish were first noted in 2011. Currently the sporadic deaths amongst mature specimens (>0.7m) persist; and the reason(s) for their demise remains unclear. Therefore, the aim was to employ a seasonal study design to investigate the health status of selected fish species such as H. molitrix in Flag Boshielo Dam by evaluating haematological parameters, oxidative stress biomarkers and bio-accumulation levels of particular transition metals. Seasonal surveys were carried out from February 2012 to January 2013 at Flag Boshielo Dam, Olifants River System, Limpopo Province. The locality surrounding the dam is known to be in an agriculture and mining catchment. Hypopthalmichtys molitrix and Labeo rosae (Steindachner, 1894) commonly known as the rednose labeo were collected with the use of scoop nets, conventional angling gear and gill nets. Following collection, morphometric measurements were taken and blood was collected. The blood samples required for further analysis at the Medical Science Department, University of Limpopo were kept on ice (4˚C). After the collection of all blood samples the specific fish was sacrificed and muscle samples were collected for bio-accumulation analysis and gills and liver samples were collected for the measurement of oxidative stress biomarkers. These tissue samples were rapidly frozen and kept frozen (-85˚C) until further analysis. Haematological parameters from the study reflected a variation amongst comparison of the inter- and intra-species. It was observed that mature H. molitrix suffered from anaemia. The response of glutathione-S-transferase (GST) and thiobarbituric acid reactive substances (TBARS) was relatively constant throughout all seasons when the young (<0.5m) and mature H. molitrix (0.6 – 0.90m) specimens were compared. However, the catalase (CAT) response of mature H. molitrix was dramatically impaired. This would increase their vulnerability to oxidative stress. Bioaccumulation levels of the eleven selected transition elements exhibited various trends. Metals such as Molybdenum (Mo), Vanadium (V), (Chromium) Cr, Cobalt (Co), Zinc (Zn), Cadmium (Cd) and Mercury (Hg) exhibited seasonal bio-accumulation levels that were in support of the various feeding behaviours of the fish species in this study. On the other hand, metals such as Manganese (Mn), Iron (Fe), Copper (Cu), Zinc (Zn), Cadmium (Cd) and Mercury (Hg) also illustrated the potential to be contributing factors in the death of the mature specimens. In conclusion, the findings from this study illustrate the complex nature of metabolic disturbances resulting in the death of mature H. molitrix specimens. It is clear that no single aspect investigated in this study could be solely implicated as the major cause of death. This multifactorial presentation necessitates further haematological assessment focussing on blood cell morphology and pathology, as well as investigations into other oxidative stress biomarkers in liver and gill tissue. In addition, identifying the most appropriate tissue type for future bio-accumulation measurements of transition metals in this feral population is necessitated. It is further suggested that neuro-muscular assessments, focussing on neurotransmitters such as γ-aminobutyric acid (GABA) and acetylcholine (Ach), form part of the investigation into the lethargic behaviour of the mature fish.

Municipal wastewater effluent (MWWE) has the potential for aquatic degradation, as it is the largest, per volume, anthropogenic discharge in Canada and other areas in the world. With an increasing population in many areas, such as Southern Ontario, there is concern that infrastructure of wastewater treatment facilities will not be able to maintain adequate treatment and prevent further degradation of the environment. The Grand River watershed, in Southern Ontario, is predicted to have its population increase to 1.2 million people by 2031 (from 780,000 people in 2001). Although wastewater treatment has improved, concern remains for receiving environments due to inadequate treatment (i.e. Kitchener) and minimal dilution (i.e. Guelph). This research was conducted to understand current impacts of MWWE in the Grand River watershed on fish communities to support future management and protection. Study sites upstream and downstream were chosen for their proximity to the Guelph, Kitchener, and Waterloo MWWE outfalls, similarity in habitat, and wadeability. Habitat analysis indicated that there were no large physical differences among sites. Fish communities were collected in a standardized method with a backpack electroshocker at each site (six randomly selected 10 m by 10 m sub-sites for 5 min). Greenside Darter (Etheostoma blennioides) and Rainbow Darter (E. caeruleum), the most abundant species, were also analyzed for stable isotope signatures (δ13C and δ15N) at each site. Downstream of the Guelph outfall there were no changes in mean total catch per unit effort (CPUE) or mean total mass. Changes to diversity, resilience, and tolerance in the fish community were attributed to a decreased abundance of Greenside Darter and increased abundance of Rainbow Darter. Downstream of the Kitchener discharge, there was a trend towards decreasing mean total CPUE, especially for darter species, and an increase in mean total mass due to a community shift to larger species including Catostomids and Centrarchids. The changes in abundance of Rainbow Darter, Catostomids, and Centrarchids among reference and Kitchener MWWE exposed sites explained the pattern in resilience, tolerance, and diet classifications. Lower diversity downstream of all three MWWE outfalls can be attributed to the increase in Rainbow Darter abundance. Stable isotope signatures (δ13C and δ15N) of Greenside Darter did not change downstream of the Guelph and Waterloo discharges, but signatures of Rainbow Darter increased immediately below the two outfalls. This shift may be due to the Rainbow Darter being able to take advantage of a change in the environment (i.e. food availability), resulting in its increased abundance and changes in isotopic signature. Directly downstream of the Kitchener outfall both darter species had an increase in δ13C and a large decrease in δ15N, likely due to high nutrient inputs from the outfall. The Kitchener wastewater discharge is also associated with a decrease in abundance of fish and a shift in community structure. MWWEs are currently affecting the aquatic environment, including fish communities in the Grand River watershed. Future investments in infrastructure and watershed management should be made to mitigate degradation of water quality in this watershed.

Municipal wastewater effluent (MWWE) has the potential for aquatic degradation, as it is the largest, per volume, anthropogenic discharge in Canada and other areas in the world. With an increasing population in many areas, such as Southern Ontario, there is concern that infrastructure of wastewater treatment facilities will not be able to maintain adequate treatment and prevent further degradation of the environment. The Grand River watershed, in Southern Ontario, is predicted to have its population increase to 1.2 million people by 2031 (from 780,000 people in 2001). Although wastewater treatment has improved, concern remains for receiving environments due to inadequate treatment (i.e. Kitchener) and minimal dilution (i.e. Guelph). This research was conducted to understand current impacts of MWWE in the Grand River watershed on fish communities to support future management and protection. Study sites upstream and downstream were chosen for their proximity to the Guelph, Kitchener, and Waterloo MWWE outfalls, similarity in habitat, and wadeability. Habitat analysis indicated that there were no large physical differences among sites. Fish communities were collected in a standardized method with a backpack electroshocker at each site (six randomly selected 10 m by 10 m sub-sites for 5 min). Greenside Darter (Etheostoma blennioides) and Rainbow Darter (E. caeruleum), the most abundant species, were also analyzed for stable isotope signatures (δ13C and δ15N) at each site. Downstream of the Guelph outfall there were no changes in mean total catch per unit effort (CPUE) or mean total mass. Changes to diversity, resilience, and tolerance in the fish community were attributed to a decreased abundance of Greenside Darter and increased abundance of Rainbow Darter. Downstream of the Kitchener discharge, there was a trend towards decreasing mean total CPUE, especially for darter species, and an increase in mean total mass due to a community shift to larger species including Catostomids and Centrarchids. The changes in abundance of Rainbow Darter, Catostomids, and Centrarchids among reference and Kitchener MWWE exposed sites explained the pattern in resilience, tolerance, and diet classifications. Lower diversity downstream of all three MWWE outfalls can be attributed to the increase in Rainbow Darter abundance. Stable isotope signatures (δ13C and δ15N) of Greenside Darter did not change downstream of the Guelph and Waterloo discharges, but signatures of Rainbow Darter increased immediately below the two outfalls. This shift may be due to the Rainbow Darter being able to take advantage of a change in the environment (i.e. food availability), resulting in its increased abundance and changes in isotopic signature. Directly downstream of the Kitchener outfall both darter species had an increase in δ13C and a large decrease in δ15N, likely due to high nutrient inputs from the outfall. The Kitchener wastewater discharge is also associated with a decrease in abundance of fish and a shift in community structure. MWWEs are currently affecting the aquatic environment, including fish communities in the Grand River watershed. Future investments in infrastructure and watershed management should be made to mitigate degradation of water quality in this watershed.

The objective of this study was to determine the relationship between fish assemblage structure and habitat in streams dominated by an agricultural landscape. Fishes from 20 natural and 20 channelized streams were sampled using electrofishing gear in East Central Indiana. Streams that had been channelized had a lower quality fish assemblage when compared to natural streams as measured by the Indiana V. Eastern Corn Belt Plain Index of Biotic Integrity (IBI). Stream habitat was evaluated using the Qualitative Habitat Evaluation Index (QHEI), which indicated that channelized streams had lower quality primarily due to a loss of heterogeneous habitat. Pearson correlation analysis relating ECB IBI and QHEI was positive and significant, and demonstrated that a reduction in riffle and pool areas associated with channelization was the most significant factor influencing the fish community. Furthermore, species lost when streams are channelized were predictable, and often represented environmentally sensitive species. The results of this study suggested that stream channel alterations have a negative and lasting influence on the fish assemblage which should be recognized prior to any stream development. / Department of Biology

I tested if spatial variation of Ohio River drainage basin fish assemblages, current habitat, water quality, and hydrology were concordant with historic glaciation boundaries. Assemblage analyses were organized using taxonomic and functional groups. Multivariate analyses, principal components analysis (PCA) and indicator species analyses, were used to test whether taxonomic and functional assemblages were distinct among regions with varying glacial histories. Principal components analysis was used to identify habitat and water quality as well as hydrologic gradients that could be discerned by glacial region. I identified significant differences in both taxonomic and functional fish assemblage structure and habitat variation among regions that had different glaciation histories. Recently glaciated Wisconsinan sites were characterized by assemblages of Cyprinidae and Catostomidae families, with high abundances of tolerant fishes that tended to occur in habitats with reduced current velocity. Sites in the Pre- Wisconsinan region were characterized by Cyprinidae, Catostomidae, Centrarchidae, and Percidae families, with increased abundances of intolerant fishes that tended to occur in habitats with coarser substrates and increased water velocity in streams of varying size. Sites in the unglaciated region were dominated by Cyprinidae and Percidae families but were not closely associated with any habitat-based functional group. Taxonomic and functional analyses explained 25% and 40%, respectively, of the variance in assemblage structure. Mean habitat PCA component scores in the unglaciated and Pre-Wisconsinan sites were significantly different than Wisconsinan sites, which were characterized by increased channel structure and reduced stream size. While a multitude of factors impact the distribution of fishes, these results suggest that historical influences such as glaciation may be used to further explain underlying mechanisms of spatial variation in fish assemblages. / Department of Biology

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