This study elucidates the Postglacial vegetational history of lowland lake sites in Gwynedd using detailed palynological work integrated with radiocarbon dating, loss-on-ignition, chemical, charcoal, and X-ray diffraction analyses. An early Postglacial phase of Juniperus-Betula scrub was succeeded by open Betula-Corylus woodland at Llyn Cororion, a kettlehole site on the Arfon Platform (SH597688). Ouercus and tilmus were established by 8600 BP and Pinus dominated locally at 8425 BP. A subsequent water level rise and fire disturbance encouraged the spread of Alnus. Tilia was established by 5650 BP. Progressive deforestation began in the Late Bronze Age with increased fire use and spread of grassland; cereals are first recorded at 2900 BP. There is evidence that Llyn Cororion was used for Cannabis retting during Mediaeval times. Postglacial vegetation at Llyn Hendref (SH398765), an exposed lake basin on Anglesey, was dominated by CoryJ.us and Alnus; mixed, open oak woodland occurred away from the lake basin but Tili p and Pinus were never abundant. In the late Postglacial there was increased fire disturbance resulting in effective soil erosion and acceleration of mire development. Mire encroachment increased around 8700 BP resulting in lake shallowing and increased sediment erosion and redistribution. Site comparison with published work (Melynllyn and Nant Ffrancon) shows that there were variations in vegetational development within North Wales. Radiocarbon dating shows that similar vegetational events were time transgressive determined by migration rates, soil conditions, competition, hydrology and altitude.

This study centres on a diverse assemblage of epilithic algal grazing fish (17 cichlids and 2 cyprinids) found on the rocky shores near Monkey Bay, Lake Malawi. Diet overlap among these species is large, but competitive exclusion is apparently avoided by the species having different feeding structures, behaviour and distribution on the shore. In many respects the ecology and behaviour of the cichlid fishes inhabiting the rocky zones of Lake Malawi parallel those of coral reef fish. In both communities there are species which are highly territorial, resulting in resource subdivision and, in some cases, the development of algal gardens. As this behaviour has not been previously reported for cichlid species, this thesis describes the territoriality of the rock-dwelling cichlids of Monkey Bay, Lake Malawi, and poses three specific questions: 1. What is the function of territoriality? 2. How do the territorial species subdivide the space resource? 3. What prevents one species taking over all the available space? It is suggested that interspecific territoriality evolved in response to a shortage of food, and, at present, serves principally to defend an algal garden i.e. a food supply of high standing crop. The species studied are extremely site specific. The rocky shore is subdivided among the four species according to the rock configuration, size, algal mat composition and position on the shore, of the available sites. An experimental study of the space utilization of the two common territorial species, referred to as 'Pseudotropheus orange cheek' and 'Pseudotropheus aggressive', showed that suitable territory sites are in short supply and that these species are in competition for some sites. These results do not support those of Fryer (1959) who suggested that a superabundance of food enabled fish to coexist by sharing the same food resource. Indeed it now appears that a shortage of food may have been a major driving force during the recent evolution of the species studied.

In Malawi, fish contribute about 60-80% to the country's animal protein supply. The greater proportion (> 50%) comes from Lake Malawi. Bathyclarias nyasensis and other clariid catfish contribute up to > 20% of the total catches. Catches of Bathyclarias nyasensis in the inshore area of the south-east arm of Lake Malawi are declining and a management plan for the fishery is essentially lacking. There is paucity of biological data that precludes the use of any option to manage the species. The principal aim of the thesis was to define the ecological role B. nyasensis, the most abundant and common of the Bathyclarias species. By examining life history characteristics within a food web context, it was hypothesized that the study would provide an insight into the interrelationships between species, and, hence form the basis for the development of a rational exploitation strategy for the species. The study was undertaken in the south-east arm of Lake Malawi (9° 30'S, 14° 30'S). The principal objectives of the study were to investigate the feeding ecology of B. nyasensis by examining morphological characters and structures associated with feeding, diet of B. nyasensis, food assimilated in the species using carbon (∂¹³C) isotope analysis, daily food consumption rate for B. nyasensis; and to relate the feeding ecology to life history traits such as age, growth, and some aspects of the reproductive biology of B. nyasensis. The suitability of sectioned pectoral spines and sagittal otoliths to age B. nyasensis was assessed. Due to reabsorption of growth zones with increasing spine lumen diameter with fish size, and the relatively low number of spines that could be aged reliably, only otoliths were used. The maximum age for B. nyasensis was estimated at 14 vears. Growth was best was described by the four parameter Schnute mc: lt ={42+(81¹·⁸ - 42¹·⁸)x1-e⁻°·°⁵⁽t⁻¹⁾}¹/¹·⁸ over 1-e⁻⁽⁻°·°⁵⁾⁽¹¹⁾ for female, lt={41+(98¹·² - 41¹·²)x 1-e⁻°·°²⁽t⁻¹⁾}¹/¹·² over 1-e⁻⁽⁻°·°²⁾⁽¹³⁾ and for male fish. Age-at-50% maturity for females and males were estimated at 7 years and 4 years, respectively. Typically, fish grew rapidly in the first year, but slower during subsequent years. Smaller fish were found inshore while larger fish were found in offshore regions. It was hypothesised that the rapid growth in the first year and slower growth later is a consequence of change in diet from high quality and abundant food source to a more dilute food and that this may be associated with a shift in habitat. Morphological characters associated with feeding were used to predict the food and feeding behaviour of B. nyasensis. The size of premaxillary, vomerine, pharyngeal dental and palatine teeth and premaxillary and vomerine tooth plates suggested the capability of B. nyasensis to handle both large and small prey, with a propensity towards smaller prey in composition to C. gariepinus. The molariform teeth on the vomerine tooth plate suggested that molluscs form part of the diet. The relative gut length (1.27±0.24) suggested omnivory, with an ability to switch between planktivory and piscivory. Buccal cavity volume and filtering area changed with fish size at 500-600 mm TL upon which it was hypothesised that the fish diet changed to planktivory at this size. Detailed diet analysis provided information upon which the above hypotheses could be accepted. Percent Index of Relative Importance (%IRI) and a multi-way contingency table analysis based on log-linear models were used to analyse diet data. Results showed that B. nyasensis is omnivorous, but with a distinct ontogenetic dietary shift from piscivory to zooplanktivory at 500 - 600 mm TL. The increased buccal cavity volume at the same fish size therefore, suggests that B. nyasensis is well adapted to filter the dilute zooplankton resource. Increased foraging costs of feeding on zooplankton explained the slower growth of larger fish. The dietary shift was finally corroborated by results of the ∂¹³C isotope analysis. A polynomial equation described the change in carbon ratios with fish size: ∂¹³C = - 33.188 + 0.4997L - 0.0045 (total length)² (r² = 0.598, n = 12, p=0.022). The ontogenetic shift in diet was synchronised with a habitat shift postulated in life history studies. In the inshore region, B. nyasensis were predominantly piscivorous (apex predators), and were zooplanktivorous in the offshore region, thereby forming part of the pelagic food web in the latter region. After examining "bottom-up" and trophic cascade theories, it was postulated that perturbations of the B. nyasensis stock would be discernible both at the top and lower trophic levels. As a piscivore and therefore apex predator, effects of overfishing B. nyasensis in the inshore region could cascade to unpredictable ecological changes in inshore areas and, due to the ontogenetic habitat shift, in the offshore regions. Examples of trophic cascade phenomena are provided. On the basis of the feeding study, it was possible to reconstruct the pelagic food web of Lake Malawi. Apart from the lakefly Chaoborus edulis, B. nyasensis is the other predator that preys heavily on zooplankton in the pelagic zone. Perturbations of the B. nyasensis stock could affect size composition of zooplankton which in tum, could affect production of C. edulis, a resource for the top predators in the food web. The findings of the present study contributed to the ongoing debate of introducing a zooplanktivore into the pelagic zone of Lake Malawi. Proponents for the introductions have argued that zooplankton predation by fish is inferior to that of C. edulis. Introduction of a clupeid zooplankton was proposed as a strategy to boost fish production in the lake. The zooplanktivore would either out-compete or prey on C. edulis to extinction. Opponents to this view argued that zooplankton biomass in the pelagic region was too low to support introductions and that the fish biomass in the pelagic region may have been underestimated. Results from the present study suggest that planktivorous fish (including B. nyasensis) might not be inferior to C. edulis in utilising the zooplankton resource; B. nyasensis is well adapted to utilise the dilute zooplankton resource, and by omitting B. nyasensis from previous studies, overall zooplankton predation by fish may have been underestimated by between 7 - 33%. On the basis of the theoretical migratory life history cycle of B. nyasensis, it is recommended that the current interest in increasing fishing effort in offshore areas should proceed with caution. Ecological changes that may have occurred in the inshore areas due to overfishing have probably not been noticed: as the offshore zone has never been fished. The latter zone may have acted as a stock refuge area. Higher fishing intensity in the offshore areas could lead to serious ecological imbalances and instability. The study has shown that life history characteristics studied in the context of the food web, and in the absence of other fisheries information and/or data, strongly advocates the precautionary principle to managing changes in exploitation patterns.

Active lava lakes present a rare opportunity to observe directly the complex processes occurring within a magma body. Situated on Ross Island, Antarctica, the 3794-m-high crater of Erebus volcano has hosted a phonolite lava lake for decades. Previous studies have shown that many of the lake’s characteristics, such as surface velocity, gas flux and gas composition, exhibit a pronounced pulsatory behaviour on a time-scale of ∼10 min. Focusing primarily on the analysis of infra-red (IR) imagery acquired from the crater rim, this dissertation considers how the periodic behaviour of the Erebus lava lake evolves over decadal time periods, how the cyclic fluctuations of the different properties are interrelated and what can be inferred about the mechanisms occurring beneath the surface of the lake from these observations. Creation of new hardware, software and methodologies to facilitate these types of observations is a strong focus of this work. Chapter 1 introduces the nature of active lava lakes, reviews previous studies of Erebus and presents in detail the research objectives that are addressed by the subsequent chapters. In Chapter 2, a new thermal camera system that was developed as part of this study is described. Designed to run autonomously at the crater-rim of Erebus, this system was installed in December 2012 and has enabled, for the first time, extended time-series of images to be acquired. Chapter 3 briefly describes some of the other hardware and software that was developed as part of this study and outlines how it has been utilised for volcano monitoring. In Chapter 4, a dataset of IR images collected between 2004–2011 is used to assess inter-annual variability in the pulsatory behaviour of the surface motion of the Erebus lava lake. The cyclic behaviour is found to be a sustained feature of the lake, and no obvious changes are observed across the time period analysed. Data collected with the camera system described in Chapter 2 are analysed in Chapter 5 and combined with measurements from other instruments to assess the correlation between the cyclic behaviours of different lake properties. Cycles in surface speed, surface elevation, gas flux and gas composition are found to be highly correlated with each other. In Chapter 6, the surface velocities calculated in the preceding chapters are revisited, and the two-dimensional structure of the flow field is analysed. Chapter 7 demonstrates how the motion tracking methodologies developed for studying the Erebus lava lake can be used to improve high time resolution sulphur dioxide flux estimates - a significant challenge faced in the study presented in Chapter 5. Finally, Chapter 8 presents a synthesis of the key findings and conclusions from the preceding chapters.

Early life history, distribution, movement, food habits and interspecific relations of five inshore species, largescale sucker (Catostomus macrocheilus), northern squawfish (Ptychocheilus oregonense), peamouth chub (Mylocheilus caurinum), red side shiner (Richardsonius balteatus), and prickly sculpin (Cottus asper), have been studied during the summers of 1959 - 1961 in Nicola Lake, British Columbia. Analyses were based on specimens periodically sampled with three types of seine nets from various inshore waters of the lake, observation of behaviour of the fish both in nature and in aquaria, and study of plankton, bottom animals and temperature conditions. After emerging, the fry of all species move to the head of the lake where there is a tendency to form an early-summer aggregation. Later, they diverge from the head of the lake along the shore. Fry of all four cypriniform species showed similar diurnal movement. They started to move into the shallow water at dawn and moved out at dusk. In the sculpin, fluctuations in numbers near shore had no direct correlation with time of a day. No species was rigorously restricted to one habitat, although different habitat preferences were observed. To a certain extent the species were separated by difference in distribution in relation to depth. These differences increase with age. A close association among fry of all species in the early summer gradually dissipated. Divergence was also observed in feeding habits of these species. In early summer they are typically plankton feeders, but towards the end of summer their interspecific feeding relations gradually become less because of the divergence in food preference, feeding places and feeding manner. These changes are in turn largely due to morphological changes, in particular those of feeding structures. Since the plankton resources seemed to be insufficient in the shallow inshore area, there may have been competition for food in early summer. Moreover, the fry may have been forced into severe competition by an early-summer aggregation at the head of the lake as well as by similarity in behaviour and habitat. An alternative approach to the problem of demonstrating interspecific relationships was made from comparison of species associations in lakes of the Fraser River drainage. A positive correlation between the surface area and the number of species suggests that the larger the lake, the greater the possibility of coexistence between these species, and that competition in small lakes may be a factor in eliminating some of the species. These findings are discussed in relation to the current controversy concerning specialization of temperate and tropical freshwater fishes. It is concluded that in large complex environments freshwater fishes are afforded the opportunity for specialization, whereas in small or simple environments, more generalized behavior leads to competition between species. / Science, Faculty of / Zoology, Department of / Graduate

The objects of the present study were to collect adequate data concerning the distribution of velocity in a typical valley glacier, to relate these to current theories of glacier flow, and if necessary to suggest modifications to these theories. Conventional field methods were used. Surface movement, both horizontal and vertical, was measured by triangulation of markers in the ice from fixed points on bedrock around the perimeter of the glacier. Movement at depth was determined by measurements in boreholes of the change of inclination with time. Seismic and gravity measurements of ice thickness were also available. The methods of measurement and computation are described and their accuracy is assessed. It was observed that the vertical velocity of the top of the pipe in each borehole is equal to that of the ice in its vicinity. Methods of analysing borehole data are critically reviewed in the light of this fact. A correction term for the curvature of the pipe is also used in the analysis. It is shown that, on the Athabaska Glacier, the longitudinal strain rate is not constant with depth, and that, for about 100 metres below the surface, the horizontal velocity is slightly greater than its surface value. Present theory does not cover these cases. Possible modifications are suggested. The assumption, sometimes made in the past, that the width of a valley glacier can be regarded as infinite, is shown to be unjustified. In the absence of a complete stress and velocity solution for the case of finite width, the stress solution is modified by the introduction of the "shape factor" in the stress solution. The relation between the second invariants of the strain rate and stress deviator tensors is compared with the simple power law as determined by laboratory experiments with ice. Comparison is made both for borehole measurements and measurements of change of surface velocity across transverse lines. Agreement is satisfactory, within the limits of experimental error, for all the borehole results and some of the surface movement results. This is interpreted as evidence that the underlying theory is not seriously in error. In particular, the basic assumptions, made by Nye, that the components of strain rate and stress deviator tensors are proportional, that the constant depends only on the second invariant of the stress deviator, and that the shear stress is only a slowly varying function of distance down the glacier, seem to be reasonable approximations. Of three laboratory flow laws, that of Glen for quasi-viscous creep gives the most satisfactory fit to the data. The fit would be improved if the mean temperature of the glacier were about -0.75°C rather than the pressure melting temperature. This point has not been checked because of technical difficulties. The results appear to show that the index in the power law is reduced at low stresses (i.e. less than about 0.5 bar). Other interpretations of the data are possible, however, so the result is not considered to be established. / Science, Faculty of / Physics and Astronomy, Department of / Graduate

Diurnal and seasonal variation in spatial distribution of fifteen species of fish were studied in Nicola Lake during summer. Maximum depth at which fish were taken was 110 ft. where only Kokanee were found. Peamouth Chub, Largescale Sucker and Prickly Sculpin were found in depths up to 80 ft. Chiselmouth were restricted to the shallow southwest basin all throughout summer. Carp fingerlings were also restricted to shallow weedy areas. All other species were available in all major regions of the lake. Young-of-the-year of Peamouth Chub, Largescale Sucker, Squawfish, Red-side Shiner and Prickly Sculpin stayed very close to shore during daylight. Fry of Kokanee, Rainbow Trout, Mountain Whitefish and Chinook Salmon appeared in areas close to stream inlets and outlets during day. Smaller size groups of fish available on the shore in daylight moved offshore at night, when larger fry and adults appeared in the shore. Young of Mountain Whitefish were dispersed in different regions of the shore at night. Variation was observed between daylight and dark distribution of different species. Adult Peamouth Chub and Redside Shiners stayed on the bottom during daylight but they invaded surface and shallow shore areas at night. Squawfish also tended to leave the bottom at night. Factors determining migration and summer distribution of fishes were investigated. Thermal stratification was unstable and had no apparent effect on vertical migration of most species. Only Squawfish avoided the hypolimnion. Dissolved oxygen was plentiful up to a depth of 96 ft. and its effect, therefore, could not be assessed. Light apparently played an important role in determining movements of fish in daylight and dark. Diurnal variation in distribution is attributed to effect of light. / Science, Faculty of / Zoology, Department of / Graduate

No abstract included. / Science, Faculty of / Earth, Ocean and Atmospheric Sciences, Department of / Graduate

The flexibility of Inuit social organization may be defined as a lack of societal preference among several different courses of action. Although the concept of flexibility has wide application to Inuit social organization this does not suggest that there is a complete lack of structure and order. Some of the parameters of flexibility are described through behaviour which is either disapproved or required. Two theses are advanced. One is that flexibility allows creative action which is potentially adaptive and/or integrative. This point is developed by showing a variety of ways in which different Inuit men in Lake Harbour effectively utilize combinations of hunting, trapping, carving and wage-labour, each in a manner unique to himself. The other thesis is that Inuit society is integrated wholly through mutually consensual dyadic relationships. There are two ways in which the importance of these relationships are shown in Inuit life. One is lack of imposed authority; the other is the rich variety of ritual and other relationships which are either based or seen to be based on the consensus of the two participants for the initiation and content, of the relationship. Local group leadership shows this clearly as men recognize a man as leader only while he provides them benefits. The characterisitc attributes of leadership (age, skill in hunting, knowledge, position as head of a large kin group and ownership of a boat) do not result in leadership if a man is unable to provide resources to others. The importance of mutually consensual dyadic relationships is shown through descriptions of rejected children and orphans, who receive what Euro-Canadians consider to be trauma-inducing abuse and rejection, yet appear to develop helathy personalities through acceptance and nurturance on the part of peers and sympathetic adults. Because of the dyadic consensual nature of Inuit social organization, its integration relies critically on Inuit voluntarily establishing ties of dependence and support. / Arts, Faculty of / Sociology, Department of / Graduate

The Osoyoos Lake problem is one of excessive algal populations creating nuisance conditions for recreation and agriculture. During the summer of 19 68 (May 28 to October 14) an extensive water sampling program was carried out to determine phytoplankton communities present and some of the physical and chemical factors influencing their growth. The lake was monitored using a system of three transects at predetermined sections across the lake and four fixed sampling locations on each transect. The sites on each transect were sampled at intervals of approximately two weeks. Mud samples were collected at each site once a month. Samples were also collected on a two week basis from various waters which eventually enter Osoyoos Lake. The purpose of this was to gain some indication of nutrients contributed to the lake by inflowing waters. Osoyoos Lake gave rise to a major blue-green alga bloom which persisted throughout June and July. This Anabaena flos-aquae bloom was followed by smaller populations of Fragilaria crotonensis, Dinobryon sertularia, a late summer pulse of A. flos-aquae, and at the southern end of the lake considerably large populations of Melosira italiea and Oscillatoria acutissima. A discussion of the geological, physical, chemical and morphological factors possibly combining to create such growths in the lake is presented. It was generally concluded that high levels of nitrogen, phosphorus, calcium and dissolved solids were favouring the enhancement of eutrophication in Osoyoos Lake. Climate, lake morphology and the edaphic factor were also favourable to productivity. There is evidence to support the statement that sewage effluent and industrial wastes are sources of phosphorus and nitrogen build-up in the lake. In addition to these sources, sewage seepage, agricultural drainage and nitrogen fixation are believed to be contributing to the accumulation of lake nitrogen. The continuous application of water to the fertilized orchards surrounding the basin is thought to be instrumental in leaching fertilizers and minerals natural to the land into the lake at an accelerated pace. / Applied Science, Faculty of / Chemical and Biological Engineering, Department of / Graduate