Magister Scientiae (Biodiversity and Conservation Biology) - MSc (Biodiv and Cons Biol) / The basic biology and ecology of Etrumeus wongratanai was investigated from samples of fish collected by jigging off Scottburgh, Kwazulu-Natal throughout 2014 and 2015. A total of 516 otoliths, 401 gonads, 140 stomachs and 163 samples of white muscle tissue was examined, and length and weight data of 3 637 fish caught between 2013 and 2016 was also analysed. Counts of annuli deposited on sagittal otoliths indicate that sampled E. wongratanai ranged from 0 to 3 y. (year/s) of age. Length-at-age for males (females) was estimated at 15.5 cm (16.2 cm) for 1 y. olds, 17.7 cm (17.4 cm) for 2 y. olds and 19.6 cm (18.8 cm) for 3 y. olds. The length at 50% maturity was estimated to be 15.6 cm for males, and 16.1 cm for females. Etrumeus wongratanai showed high gonadosomatic index values from June to December indicating that the breeding season lasts for 6 and 8 months for males and females, respectively, and that spawning takes place from the onset of winter to early summer. Condition factor was lowest in May through to August and increased from September. The low condition factor values from May through to August could be due to the physiological strain before and during the spawning season. Fish larvae were the most important food item in samples collected in summer, whereas eucalanids were the most important prey item in autumn and winter. Overall, large copepods were the dominant prey items in terms of frequency and importance. Stable isotope data suggests that there are gradual changes in the trophic level and diet of E. wongratanai as it increases with size, and whilst δ¹⁵N values differed between seasons δ¹³C did not. The results obtained here are compared with other species of Etrumeus, regionally and globally. / National Research Foundation (NRF) and ACEP Phulisa

The Saskatchewan River Delta (SRD) in central Canada, North America’s largest inland delta, is an important spring and fall stopover site for waterfowl with thousands flocking there annually to stage. However there is very little information on their origins prior to arrival and their feeding ecology while in the Delta. To date, band recoveries are largely from birds banded south of the SRD, mostly due to limited banding activity in productive waterfowl habitats to the north such as the Peace-Athabasca Delta and the broader boreal forest. There is also very little information on the importance of the SRD as an overall recruitment area for the North American waterfowl population. No studies have used stable isotopes to infer the origins and diets of these birds. I first used stable isotopes of hydrogen (2H) and sulfur (34S) to infer migratory origins and specifically evaluate the contribution of local and non-local birds to the staging population in the SRD during fall migration. Based on 2H, I found that few birds (34%) originated in the SRD despite its known role as breeding habitat; instead, most birds (56%) were migrants from the north of the SRD and a small fraction (10%) came from south of the SRD. Stable sulfur isotope data proved a useful tool in further delineation of birds into prairie and forest regions, respectively. Secondly, I used stable carbon (13C) and nitrogen (15N) isotopes and mercury concentrations in liver tissue ([Hg]) to trace nutrient sources of these waterfowl using the SRD prior to fall migration, and tested for differences in diets among species, sexes and age groups within species. I demonstrated the importance of macrophytes as a source of food, particularly among the American Widgeon and Northern Pintail (70% of the diet). However, there was some level of partitioning of resources at the species level, as Blue-winged Teal and Green-winged Teal used invertebrate sources, as did a distinct group of Mallards. This is likely a result of birds minimizing competition for resources during the short staging period in the SRD when waterfowl densities are high. Finally, I found that 15N values in liver, a known indicator of trophic position, can be confounded by variation in basal sources; hence, there is the need to use other isotopes or tracers such as [Hg] for verification. Overall, my results suggest an important role for northern ecosystems in central Canada in contributing to the waterfowl breeding population in the Central Flyway, and a key role for the SRD in providing fuel for waterfowl during fall migration. .

Amphibian diversity has declined, in part, due to the infectious disease chytridiomycosis, caused by the fungal pathogen Batrachochytrium dendrobatidis (Bd). Andean water frogs in the genus Telmatobius are particularly vulnerable to the disease and the genus has been extirpated from Ecuador and in Andean cloud forests, yet populations of species persist in the high Andes of Peru and Bolivia. The Alpaca Water Frog (Telmatobius intermedius), endemic to the Peruvian Andes, can be found infected with Bd. Alpaca Water Frogs inhabit high elevation open canopy freshwater systems. My overall goal was to study the effect of chytrid infection on the trophic ecology of Telmatobius tadpoles. I used stable isotope ratios of carbon (δ13C) and nitrogen (δ15N) to characterize the the trophic structure and energy flow in this system. I observed the values of δ15N were higher for tadpoles than algal material (t-test, t= -8.60, df= 34, p< 0.01), mayfly nymphs (t-test, t= 5.25, df= 30, p< 0.01), and predatory aquatic invertebrates (t-test, t= -4.18, df= 47, p< 0.01). In regard to the δ15N values of tadpoles and frogs, tadpoles had a lower value (t-test, t= -3.0, df= 31, p< 0.01). Values of δ15N in tadpoles were relatively high, signaling the presence of animal tissue in their diet. I also investigated changes in tadpole diet associated with mouthpart deformities caused by the fungal pathogen Bd. There was a positive association between the extent of mouthpart deformity and Bd infection (Fisher’s Exact test, p<0.001). The relative proportions of diatom morphotaxa groups found in the foregut of T. intermedius tadpoles varied in association with the degree of mouthpart deformity, as indicated by an ANOSIM analysis (R=0.875, p<0.001). Finally, in addition to Bd prevalence in adult aquatic frogs, I investigated whether Alpaca Water Frogs and other Andean Water Frogs tested positive for the antifungal bacterium Janthinobacterium lividum (Jliv). My results show that 57% of the sampled frogs were infected with Bd, 12.5% of frogs hosted both Jliv and Bd, while 7.2% hosted just Jliv. We found that the probability of an individual being infected with Bd was independent of the presence of Jliv; however, we did detect a protective effect of Jliv with respect to intensity of infection. My findings demonstrate that the fungal pathogen Bd influences the trophic ecology of tadpoles of Andean water frogs.

Drylands occupy about one-third of the world's land surface area and rivers in these regions have less predictable flow regimes than those in humid tropical and temperate regions. Australia's dryland river-floodplain systems cycle through recurrent periods of floods and droughts, oflen resulting in extreme hydrological variability. As a result, these systems have been described as having a 'boom and boost' ecology with periods of high productivity associated with flooding. Not surprisingly, flow and its variability have been recognised as major driving forces in the ecological functioning of Australian rivers and responses to flow variability from fish and aquatic invertebrates have been reasonably well described. Furthermore, the reduced amount of water reaching floodplain waterbodies due to river regulation has been held responsible for successional changes in aquatic biota and, consequently, the resources available for both fish and invertebrates. However, information regarding the impacts of water resource development has generally focused on within-channel processes of Australian rivers, not on floodplains, which are arguably more affected by water development. The following dissertation is concerned with how different types of natural and modified floodplain lagoons are able to trophically support their fish communities in the floodplain of the Macintyre River, Border Rivers catchment (QLD/NSW), a regulated dryland river. This study focuses on the influence of flooding and the implications of an extended dry period, and different levels of flow regulation, on the feeding ecology of selected fish species (Ambassis agassizil, Lelopotherapon unicolor and Nematalosa erebi) between 2001 and 2003. Food resources consumed by fish are hypothesised to vary in response to flooding, when inundation of isolated lagoons and vast floodplain areas can result in a burst of primary and secondary productivity. Given the permanently elevated water levels of some regulated floodplain lagoons, fish diets are hypothesised to be less variable in these floodplain habitats in comparison to diets of fish from floodplain lagoons with natural flow and water regime. Feeding ecology is examined firstly, in terms of diet composition of selected fish species, using stomach content analysis, and secondly, in relation to possible energy sources sustaining fish (using stable isotope analysis) in selected floodplain lagoons and a site in the main channel of the Macintyre River. The information produced should allow managers to take variations in food resources, food web structure and dietary ecology into account in management regimes for refugia and dryland systems in general. Factors such as diel and ontogenetic variations in dietary composition and food intake by fish are shown to considerably affect ovemll dietary patterns of each study species. Therefore, it is important to understand the contributions of such factors to the variability of fish dietary patterns before performing studies on resource use by fish in floodplain habitats of the Macintyre River. Major food categories consumed by the study species were zooplankton, aquatic invertebrates and detrital material. Zooplankton was of particular importance as this food item was ingested by all three study species at some stage of their life history. Spatial and temporal variation in diet composition of the study species was mostly associated with changes in prey items available across floodplain habitats and between seasons (summer/winter). The low magnitude of flooding events during the study period is arguably the most likely factor influencing the lack of patterns of variation in fish diets in floodplain habitats subject to flooding, whereas in non-flooded lagoons the observed dietary variation was a consequence of successional changes in composition of the aquatic fauna as the dry season progressed. Water regime had an important effect on differences in fish diet composition across lagoons, but further evaluation of the influence of flooding is needed due to overall lack of major flooding events during the study period. Autochthonous resources, namely plankton, were the basis of the food web and phytoplankton in the seston is the most likely ultimate energy source for fish consumers, via planktonic suspension feeders (zooplankton). Nevertheless, organic mailer could not be disregarded as an important energy source for invertebrates and higher consumers. In general, the present study does not provide support for the major models predicting the ftinctioning of large rivers, such as the River Continuum Concept and Flood Pulse Concept, which argue that allochthonous organic matter either from upstream or from the floodplain are the most important sources of carbon supporting higher consumers. In contrast, the Riverine Productivity Model would be more appropriate to describe the food web and energy sources for consumers in the Macintyre River floodplain as this model suggests that local productivity, based on autochthonous phytoplankton and organic matter, ftiels food webs in large rivers. The results of this study suggest that factors known to affect phytoplankton production in floodplain lagoons (e.g. flow regulation, turbidity and nutrient/herbicide inputs) must be seriously considered in current landscape and water management practices.

Trophic ecology is a key component in describing patterns of variation between and within populations, particularly in Arctic marine systems wherein climate change is impacting food webs. This thesis investigates the trophic ecology of Arctic char (Salvelinus alpinus) in the Cumberland Sound region using a multi-indicator approach. My data show trophic niche differences between resident and anadromous ecotypes and evidence for estuarine feeding by residents. I document a shift in the marine diet of Arctic char from zooplankton to capelin (Mallotus villosus) – a novel prey species in this region – that has occurred in less than a decade. Changes in Arctic char growth imply population-level effects of this shift; however, more research is required. Finally, I find lipid effects on δ13C and lipid-extraction effects on δ15N and δ34S for Arctic char muscle tissue. Lipid-correction models did not provide adequate δ13C estimates; thus, chemical extraction or ecotype-specific validation of models is recommended.

Trophic ecology is a key component in describing patterns of variation between and within populations, particularly in Arctic marine systems wherein climate change is impacting food webs. This thesis investigates the trophic ecology of Arctic char (Salvelinus alpinus) in the Cumberland Sound region using a multi-indicator approach. My data show trophic niche differences between resident and anadromous ecotypes and evidence for estuarine feeding by residents. I document a shift in the marine diet of Arctic char from zooplankton to capelin (Mallotus villosus) – a novel prey species in this region – that has occurred in less than a decade. Changes in Arctic char growth imply population-level effects of this shift; however, more research is required. Finally, I find lipid effects on δ13C and lipid-extraction effects on δ15N and δ34S for Arctic char muscle tissue. Lipid-correction models did not provide adequate δ13C estimates; thus, chemical extraction or ecotype-specific validation of models is recommended.

京都大学 / 新制・課程博士 / 博士(地球環境学) / 甲第23351号 / 地環博第209号 / 新制||地環||40(附属図書館) / 京都大学大学院地球環境学舎地球環境学専攻 / (主査)教授 德地 直子, 教授 柴田 昌三, 准教授 西川 完途 / 学位規則第4条第1項該当 / Doctor of Global Environmental Studies / Kyoto University / DGAM

Artificial reefs may enhance the biological production of reef-associated flora and fauna, but their trophic structure relative to that of natural reefs remains understudied. We assessed trophic dynamics by comparing δ13C and δ15N in 43 fish species from artificial and natural reef tracts of Broward County, Florida. We tested the effect of sampling location (artificial, first, and second reef), general feeding strategy (herbivore, omnivore, planktivore, invertivore, and carnivore), phylogeny, and standard length. For all samples, δ13C and δ15N ranged from -19.5 to -13.1‰ and 6.7 to 13.3‰, respectively. Lower trophic level feeding behavior resulted in more depleted δ13C and δ15N and higher trophic level feeding behavior resulted in more enriched δ13C and δ15N. We detected significant effects of both general feeding strategy and phylogeny. We also detected significant differences in δ13C and δ15N profiles between artificial and natural reefs; however, these differences were not great enough to suggest changes in the feeding strategy or trophic dynamics of individual fish taxa.

As relações entre o tamanho dos indivíduos de uma espécie e suas consequências anatômicas, fisiológicas e ecológicas são denominadas relações alométricas. Nesse sentido, diversos trabalhos avaliam a influência do tamanho da fêmea de répteis em características relacionadas à sua reprodução, ao que chamamos de alometria reprodutiva. A variação no tamanho dos indivíduos de uma espécie e do investimento reprodutivo das fêmeas pode ser atribuída, dentre outros fatores, a diferenças na qualidade do alimento consumido. No presente estudo utilizamos medidas dos rastros, do tamanho do corpo, da ninhada e do ovo de tartaruga-verde, Chelonia mydas, para avaliar a influência do tamanho da fêmea no investimento reprodutivo. Realizamos também análise de isótopos estáveis de 13C e 15N de diferentes tecidos das fêmeas para avaliar a influência da dieta (recente e antiga) no seu investimento reprodutivo. Coletamos os dados na Ilha da Trindade, principal área de nidificação da espécie em território brasileiro e situada no Sudoeste Atlântico, há aproximadamente 1140 km da costa central do Brasil. Verificamos que fêmeas de níveis tróficos mais altos, ou seja, que incluem itens alimentares de fonte animal em sua dieta, tendem a ser maiores e a produzirem maior quantidade de ovos. Foram estabelecidas equações para estimar o tamanho da fêmea a partir da largura de seu rastro e equações para estimar o tamanho da ninhada a partir do tamanho da fêmea, métricas que poderiam ajudar no monitoramento do sucesso reprodutivo de C. mydas na Ilha da Trindade / Allometric relationships describe anatomical, physiological and ecological variations according to body size The influence of size of females in reptiles in characteristics related to their reproduction, i.e. reproductive allometry, was evaluated is several papers. Variations in size of individuals of a given species and female\'s investment in reproduction may be attributed, among other factors, to differences in quality of consumed food. In the present study we have used data on turtle\'s track width, body size and clutch size of the green turtle Chelonia mydas to evaluate the influence of female\'s size on reproductive investment. We have also performed 13C and 15N stable isotopes analysis of different body tissues of females to evaluate the influence of diet (recent and past) on reproductive investment. Data were collected in Trindade Island, the main nesting areas of C. mydas in the Brazilian territory, which is situated in the SW Atlantic, 1140 km away from the central coast of Brazil. We have verified that females from higher trophic levels, i.e. the ones including more food from animal origin in their diet, were bigger and produced larger clutches. Equations were build to estimate female\'s size from track width and clutch size from female\'s size. These metrics could help in the monitoring of the reproductive success of C. mydas in Trindade Island

A introdução de espécies nos ecossistemas pode levar a conseqüências difíceis de serem controladas, sendo que a competição por recursos alimentares talvez seja o principal meio pelo qual uma espécie introduzida possa afetar as espécies nativas, podendo ocasionar a extinção. Neste sentido, os estudos de alimentação tornam-se importantes ao fornecerem subsídios para compreender o funcionamento trófico de um ecossistema. Considerando estes aspectos, o objetivo da pesquisa foi conhecer a ecologia trófica das espécies introduzidas (Plagioscion squamosissimus e Cichla cf. ocellaris) e da espécie nativa (Geophagus brasiliensis), avaliando as possíveis interações entre elas. Para o estudo da dieta das espécies escolhidas, foram utilizados os exemplares capturados durante o desenvolvimento do projeto PROBIO 2. As coletas foram realizadas nos seis reservatórios do Médio e Baixo rio Tietê, no período de novembro de 2002 a fevereiro de 2004. Foram realizadas análises quantitativas (freqüência de ocorrência, método volumétrico e método gravimétrico) dos itens encontrados, caracterizando a preferência alimentar das espécies. Neste trabalho o acará (Geophagus brasiliensis), apresentou um hábito alimentar onívoro, consumindo principalmente larvas de Diptera, insetos aquáticos e microcrustáceos. A espécie (Cichla cf. ocellaris) apresentou um hábito alimentar piscívoro, consumindo principalmente peixes e crustáceos. A corvina (P. squamossisimus) foi considerada piscívora, apresentando um amplo espectro alimentar, consumindo principalmente peixes, insetos aquáticos e crustáceos. A ampla distribuição da espécie P. squamosissimus nos seis reservatórios do médio e baixo rio Tietê e a plasticidade alimentar evidenciada pela análise de conteúdo estomacal sugerem que a corvina exerce uma forte pressão sobre as espécies nativas, cuja dinâmica populacional pode ser alterada. / The species introduction into the ecosystems may lead to difficult consequences hard to be controlled and the competition for food resources being the main factor by which introduced species can affect the native species, even causing their extinction. In this sense, the feeding studies are important by supplying subsidies to understand the trophic functioning of an ecosystem. Considering these aspects, the objective of this research was to know the trophic ecology of the introduced species Plagioscion squamosissimus and Cichla cf. ocellaris and of the native species (Geophagus brasiliensis), evaluating the possible interactions between them. For the diet study of the chosen species, were used the samples collected during the development of the project PROBIO 2. Sampling was carried out in six reservoirs of the Middle and Low Tietê river, between November 2002 and February 2004. Qualitative analysis was done (occurrence frequency, volumetric method e gravimetric method) on the found items, characterizing the species feeding preference. In this work, the acará (Geophagus brasiliensis) presented an omnivorous feeding habit, mainly consuming Dipteral worms, aquatic insects and micro crustaceans. The species (Cichla cf. ocellaris) presented a piscivorous feeding habit, mainly consuming fishes and crustaceans. The curvina (P. squamossisimus) was considered piscivorous, presenting an ample feeding spectrum, mainly consuming fishes, aquatic insects and crustaceans. The ample distribution of the specie P. squamosissimus in the six reservoirs of the Middle and Low Tietê river and the plasticity revealed by the stomach content analysis, suggests that the curvina exercises a strong pressure over the native species, in which population dynamics can be changed.