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In this study ¹³C/¹²C and ¹⁵N/¹⁴N ratios were measured from 𝘔𝘪𝘤𝘳𝘰𝘱𝘵𝘦𝘳𝘶𝘴 𝘥𝘰𝘭𝘰𝘮𝘪𝘦𝘶 tissue, from all stages throughout the fish's lifecycle. The different stages in the life of 𝘔𝘪𝘤𝘳𝘰𝘱𝘵𝘦𝘳𝘶𝘴 𝘥𝘰𝘭𝘰𝘮𝘪𝘦𝘶 are represented also by shifts in the trophic level of the fish. As embryos, the δ¹⁵N and δ¹³C values for 𝘔𝘪𝘤𝘳𝘰𝘱𝘵𝘦𝘳𝘶𝘴 𝘥𝘰𝘭𝘰𝘮𝘪𝘦𝘶 tissues are dependent on the δ¹⁵N and δ¹³C of the mother. Also until the point of metamorphosis, where the yolk sac is completely used up, the isotopes reflected in the tissues represent a combination of the δ¹⁵N and δ¹³C of the yolk and any plankton which the young fish are able to feed on. As the fish grows and its diet changes to crayfish and other smaller fish the isotopes reflected in the 𝘔𝘪𝘤𝘳𝘰𝘱𝘵𝘦𝘳𝘶𝘴 𝘥𝘰𝘭𝘰𝘮𝘪𝘦𝘶 shift as the fish effectively increases its trophic position. Definite trends were seen in the δ¹⁵N values throughout the entire lifecycle of 𝘔𝘪𝘤𝘳𝘰𝘱𝘵𝘦𝘳𝘶𝘴 𝘥𝘰𝘭𝘰𝘮𝘪𝘦𝘶, and while the δ¹³C values did not produce such definite trends it was discovered that there was an overlying spatial trend represented in the δ¹³C values. This means that Micropterus dolomieu of similar age and size display an obvious offset in their δ¹³C values depending on their location in the lake. Also addressed here are the potential problems related to working with preservative chemicals and the effects they have on isotope ratios. Shifts were not only seen in both δ¹⁵N and δ¹³C (as has been addressed in the past) but also between different batches of the same preservative fluid. Different batches of formalin can potentially give different offsets to both δ¹⁵N and δ¹³C, making it necessary to calibrate offsets given by all batches of formalin used throughout the entire procedure. / Thesis / Master of Science (MS)

Humans have indirectly and directly contributed to the extinction of over 500 species within the past 500 years, a rate far higher than we have seen in the past. The high extinction rate and the fact that 18% of vertebrates may become extinct within the next century have pushed Earth into a biodiversity crisis. Understanding what makes species more at risk of extinction is needed to protect Earth’s biodiversity. Generally, it is expected that predators have greater extinction risk than omnivores and herbivores because predators are larger in body size, depend on other animal species for food, need large home ranges, and have fewer individuals within their populations. However, no study to date has actually tested the assumption that predators have the highest extinction risk. This question is important to understand because diet is associated with the ecological role a species plays in an ecosystem. We compared the extinction risk of species with different diets to determine species in which trophic level are proportionately more at risk of extinction. We classified each species’ diet, trophic level (i.e.,predator, omnivore, and herbivore), body size, habitat, geographic region, system, and associated threats. We focused our analyses on all mammals, birds, and reptiles assessed by the International Union for the Conservation of Nature. We then compared the expected and observed proportions of threatened species within each trophic level and diet group at global, system, habitat, and regional scales. We found that predators, except scavengers, fish-eating birds, and obligate mammal and bird eaters, were not more threatened than expected. On the other hand, herbivores consistently had greater proportions of threatened species than expected. Specifically within herbivores, fruit, grass, and leaf-eating species had high proportions of threatened species. When we separated large-bodied and small-bodied species, we found that most large-bodied species, regardless of their trophic level, had greater proportions of threatened species. When we looked at the regions and habitats where species were more often threatened, we found that herbivores were highly threatened in south and Southeast Asia, sub-Saharan Africa, and Oceania. In addition, herbivores were highly threatened in tropical forests, marine coasts, and sometimes grasslands. Overall, terrestrial herbivores and marine predatory birds were highly threatened. We found that these patterns may have resulted from overexploitation, habitat alteration, and pollution targeting herbivores and sometimes omnivores. These findings suggest that we should shift conservation focus from predators to include herbivores. The most threatened species, tropical herbivores, scavengers, and mammal, bird, and fish eaters should be of highest conservation priority.

Arctic ecosystems are vulnerable to human-induced changes such as increases in contaminant levels and climatic warming. To predict effects of these changes, it is important to understand trophic relationships among Arctic organisms and how they change in response to time and environmental perturbations. Seabird diet can reflect relative availability and abundance of planktivorous fish and zooplankton in remote areas. The measurement of naturally occurring stable isotopes presents an alternative approach to evaluating dietary patterns of seabirds at both an individual level and at a larger, ecosystem level. Relative changes in δ13C values provided an indication of changes in consumption of benthic vs. pelagic prey and changes in δ15N values provided an indication of changes in trophic level.<p>I investigated trophic positions of four seabirds (Thick-billed Murres (<i>Uria lomvia</i>); Northern Fulmars (<i>Fulmarus glacialis</i>); Black-legged Kittiwakes (<i>Rissa tridactyla</i>); and Glaucous Gulls (<i>Larus hyperboreus</i>)) at Prince Leopold Island, Nunavut, 1988 2003, using my own and previously measured stable isotope measurements in blood samples. Trophic level and space use among years differed within and among species and may be related to ice conditions and species-specific foraging strategies. The species with the most flexible foraging methods, Thick-billed Murres, varied their foraging location and trophic level the most. In 2002, fewer chicks than average for all species were fledged and Thick-billed Murre chicks were lighter than in other years; however, only murres showed a concurrent decrease in the proportion of fish in their diet. Adult body condition of murres in 2002 was positively correlated with trophic level. Breeding season dietary patterns of Thick-billed Murre adults and chicks were examined on Coats Island, Nunavut, Canada, in 2004. Adult trophic level increased slightly through the breeding season and δ13C values indicated a switch from benthic to pelagic foraging locations. Chick and adult murres did not differ in either δ15N or δ13C values; however, within a family (two parents, one chick), chicks were fed at or slightly below adult trophic level. I found little variation in stable isotope values which suggests adult murres did not preferentially select prey for either themselves or their chicks. <p>Finally, stable isotope analysis was used to investigate winter foraging ecology of three species of alcids (Thick-billed Murres; Common Murres (<i>U. aalge</i>) and Razorbills (<i>Alca torda</i>)), off Newfoundland, Canada, 1996 2004. Thick-billed Murres fed at a higher trophic level than Common Murres. Razorbill δ15N values were highly variable and overlapped those of both murre species. I found no significant differences in δ13C values among the three species confirming a common spatial feeding pattern. Both murre species became depleted in 13C during winter suggesting foraging location or prey species shifted from nearshore to offshore. For Common Murres, hatching-year individuals fed at a higher trophic level and foraged farther offshore than after-hatch year birds. For Thick-billed Murres, I contrasted trophic level determined for the breeding colony at Prince Leopold Island with those determined for winter over four years and found considerable inter-annual variation in patterns of seasonal difference in trophic level. However, the proportion of lower trophic level (amphipod) vs. higher trophic level (fish) prey was generally greater in the winter than the summer.

Conservation biology would benefit from methods that identify species at risk in a proactive manner, rather than through post-hoc conservation assessments. This study examines the utility of four potential indices for predicting vulnerability in fishes: total body length; trophic level; intrinsic vulnerability score; and, resilience. Statistical analysis was done to determine if correlations existed between any of these four indices and known levels of risk in marine and freshwater Canadian fishes. Results show the success of two of these indices to predict risk: fished species over 78.33 centimeters total length, or with intrinsic vulnerability scores over 57.41 are more highly vulnerable to becoming at risk. Over 20% of Canadian fished species of unknown conservation status are therefore currently vulnerable, and possibly at risk of extinction. This study shows vulnerability indices allow a rapid prioritization of fishes at risk of extinction, and can thus help achieve proactive conservation even in the absence of population decline data.

Conservation biology would benefit from methods that identify species at risk in a proactive manner, rather than through post-hoc conservation assessments. This study examines the utility of four potential indices for predicting vulnerability in fishes: total body length; trophic level; intrinsic vulnerability score; and, resilience. Statistical analysis was done to determine if correlations existed between any of these four indices and known levels of risk in marine and freshwater Canadian fishes. Results show the success of two of these indices to predict risk: fished species over 78.33 centimeters total length, or with intrinsic vulnerability scores over 57.41 are more highly vulnerable to becoming at risk. Over 20% of Canadian fished species of unknown conservation status are therefore currently vulnerable, and possibly at risk of extinction. This study shows vulnerability indices allow a rapid prioritization of fishes at risk of extinction, and can thus help achieve proactive conservation even in the absence of population decline data.

Arctic ecosystems are vulnerable to human-induced changes such as increases in contaminant levels and climatic warming. To predict effects of these changes, it is important to understand trophic relationships among Arctic organisms and how they change in response to time and environmental perturbations. Seabird diet can reflect relative availability and abundance of planktivorous fish and zooplankton in remote areas. The measurement of naturally occurring stable isotopes presents an alternative approach to evaluating dietary patterns of seabirds at both an individual level and at a larger, ecosystem level. Relative changes in δ13C values provided an indication of changes in consumption of benthic vs. pelagic prey and changes in δ15N values provided an indication of changes in trophic level.<p>I investigated trophic positions of four seabirds (Thick-billed Murres (<i>Uria lomvia</i>); Northern Fulmars (<i>Fulmarus glacialis</i>); Black-legged Kittiwakes (<i>Rissa tridactyla</i>); and Glaucous Gulls (<i>Larus hyperboreus</i>)) at Prince Leopold Island, Nunavut, 1988 2003, using my own and previously measured stable isotope measurements in blood samples. Trophic level and space use among years differed within and among species and may be related to ice conditions and species-specific foraging strategies. The species with the most flexible foraging methods, Thick-billed Murres, varied their foraging location and trophic level the most. In 2002, fewer chicks than average for all species were fledged and Thick-billed Murre chicks were lighter than in other years; however, only murres showed a concurrent decrease in the proportion of fish in their diet. Adult body condition of murres in 2002 was positively correlated with trophic level. Breeding season dietary patterns of Thick-billed Murre adults and chicks were examined on Coats Island, Nunavut, Canada, in 2004. Adult trophic level increased slightly through the breeding season and δ13C values indicated a switch from benthic to pelagic foraging locations. Chick and adult murres did not differ in either δ15N or δ13C values; however, within a family (two parents, one chick), chicks were fed at or slightly below adult trophic level. I found little variation in stable isotope values which suggests adult murres did not preferentially select prey for either themselves or their chicks. <p>Finally, stable isotope analysis was used to investigate winter foraging ecology of three species of alcids (Thick-billed Murres; Common Murres (<i>U. aalge</i>) and Razorbills (<i>Alca torda</i>)), off Newfoundland, Canada, 1996 2004. Thick-billed Murres fed at a higher trophic level than Common Murres. Razorbill δ15N values were highly variable and overlapped those of both murre species. I found no significant differences in δ13C values among the three species confirming a common spatial feeding pattern. Both murre species became depleted in 13C during winter suggesting foraging location or prey species shifted from nearshore to offshore. For Common Murres, hatching-year individuals fed at a higher trophic level and foraged farther offshore than after-hatch year birds. For Thick-billed Murres, I contrasted trophic level determined for the breeding colony at Prince Leopold Island with those determined for winter over four years and found considerable inter-annual variation in patterns of seasonal difference in trophic level. However, the proportion of lower trophic level (amphipod) vs. higher trophic level (fish) prey was generally greater in the winter than the summer.

Polybrominated flame retardants (BFRs), organochlorine pesticides (OCPs) and polychlorinated biphenyls (PCBs) were analysed in eggs of various wild bird species from industrialised areas in South Africa. Eggs were collected during the 2008 – 2009 breeding season, homogenised and sent to the Norwegian School of Veterinary Science (NVH) for gas chromatography-mass spectrometry (GC-MS) analysis. The concentration, contamination profile, and risk assessment were conducted for each pollutant class, while effects of species-specific variation, feeding guild, and feeding habitat were investigated. Levels of BFRs ranged between 2.6 – 44 ng g-1 wet mass (wm). The predominant congeners were BDE-153, -154, - 183 and -47. Results indicated species, in close contact to humans, had higher levels of BFRs, even at lower trophic levels. Therefore, diet was not the primary route of exposure. High concentrations and the occurrence of nona-PBDE congeners and HBCD indicated exposure to current use BFRs. There were measurable levels of OCPs and PCBs in all eggs analysed. Median OCP concentration ranged from 4.2 – 623 ng g-1 wm. DDE was the predominant compound in all species with the exception of the Crowned Lapwing (Vanellus coronatus) where chlordanes were predominant. This may indicate a species-specific attribute in the metabolic efficiency or diet of the genus, since these findings have been reported elsewhere in literature. Congener profiles indicated historic sources of lindane and DDT, while low levels of p,p’-DDT in al species indicate long-range or atmospheric transport. Even though levels of p,p’-DDE were approaching toxicological thresholds, no eggshell thinning was evident. Concentrations of OCPs and PCBs showed an increase with increasing tophic level. PCB concentrations ranged between 0.9 – 296.4 ng g-1 wm. When studying the metabolic potential of PCBs, metabolic groups showed good agreement with the biodegradability of the individual congeners. Phenobarbital-type (PB-type) inducer PCBs were prevalent, indicating the predominance of less toxic PCB congeners. However, non-ortho PCBs were not analysed. These congeners aslo could impact on the toxic potential of PCBs in wild bird eggs. Principle component analysis (PCA) indicated that variances within datasets could be attributed to congener profiles within species as they were affected by exposure, diet, position in the food web, and association with human activities. Although the individual groups of organohalogens were below no observed effect levels (NOELs), negative effects could occur through interactions of various compounds with each other, as well as the unique exposure profiles of South African bird populations. To assess the dietary exposure of low-income human populations living close to large industries, the occurrence of organohalogens was investigated in backyard chicken eggs. Levels of dioxins in these eggs were above the European Union (EU) recommended limits, whereas BFRs and OCPs levels were below levels of concern. Nevertheless, areas where DDT is actively applied to dwellings for malaria control should be urgently investigated. The presence of measureable levels of all the compounds considered, indicate an environment seriously impacted by anthropogenic activity that in the long term could negatively affect both the environment and human health, if it has not already done so. / Thesis (Ph.D. (Environmental Science))--North-West University, Potchefstroom Campus, 2011.

Polybrominated flame retardants (BFRs), organochlorine pesticides (OCPs) and polychlorinated biphenyls (PCBs) were analysed in eggs of various wild bird species from industrialised areas in South Africa. Eggs were collected during the 2008 – 2009 breeding season, homogenised and sent to the Norwegian School of Veterinary Science (NVH) for gas chromatography-mass spectrometry (GC-MS) analysis. The concentration, contamination profile, and risk assessment were conducted for each pollutant class, while effects of species-specific variation, feeding guild, and feeding habitat were investigated. Levels of BFRs ranged between 2.6 – 44 ng g-1 wet mass (wm). The predominant congeners were BDE-153, -154, - 183 and -47. Results indicated species, in close contact to humans, had higher levels of BFRs, even at lower trophic levels. Therefore, diet was not the primary route of exposure. High concentrations and the occurrence of nona-PBDE congeners and HBCD indicated exposure to current use BFRs. There were measurable levels of OCPs and PCBs in all eggs analysed. Median OCP concentration ranged from 4.2 – 623 ng g-1 wm. DDE was the predominant compound in all species with the exception of the Crowned Lapwing (Vanellus coronatus) where chlordanes were predominant. This may indicate a species-specific attribute in the metabolic efficiency or diet of the genus, since these findings have been reported elsewhere in literature. Congener profiles indicated historic sources of lindane and DDT, while low levels of p,p’-DDT in al species indicate long-range or atmospheric transport. Even though levels of p,p’-DDE were approaching toxicological thresholds, no eggshell thinning was evident. Concentrations of OCPs and PCBs showed an increase with increasing tophic level. PCB concentrations ranged between 0.9 – 296.4 ng g-1 wm. When studying the metabolic potential of PCBs, metabolic groups showed good agreement with the biodegradability of the individual congeners. Phenobarbital-type (PB-type) inducer PCBs were prevalent, indicating the predominance of less toxic PCB congeners. However, non-ortho PCBs were not analysed. These congeners aslo could impact on the toxic potential of PCBs in wild bird eggs. Principle component analysis (PCA) indicated that variances within datasets could be attributed to congener profiles within species as they were affected by exposure, diet, position in the food web, and association with human activities. Although the individual groups of organohalogens were below no observed effect levels (NOELs), negative effects could occur through interactions of various compounds with each other, as well as the unique exposure profiles of South African bird populations. To assess the dietary exposure of low-income human populations living close to large industries, the occurrence of organohalogens was investigated in backyard chicken eggs. Levels of dioxins in these eggs were above the European Union (EU) recommended limits, whereas BFRs and OCPs levels were below levels of concern. Nevertheless, areas where DDT is actively applied to dwellings for malaria control should be urgently investigated. The presence of measureable levels of all the compounds considered, indicate an environment seriously impacted by anthropogenic activity that in the long term could negatively affect both the environment and human health, if it has not already done so. / Thesis (Ph.D. (Environmental Science))--North-West University, Potchefstroom Campus, 2011.