M.Sc. / Please refer to full text to view abstract

Thesis (M.Sc. (Aquaculture)) -- University of Limpopo, 2012 / The feeding habits of a macrophagous fish, Tilapia rendalli, were investigated at an oligotrophic dam that has no macrophytes, Flag Boshielo Dam. This dam supports a significant population of the macrophagous, Tilapia rendalli. The diet of T. rendalli was investigated by examining the frequency of occurrence of different food items in the stomach of the fish over a period of twelve months. A size related dietary shift was evident. The diet of juvenile fish (<5 cm) was dominated by zooplankton and the diet of adult fish (>15 cm) was predominantly marginal vegetation, particularly Cyperus sexangulasris and Panicum schinzi. However, dietary overlaps between the different size groups were evident. The diversity of food items increased with fish size until the fish were 15 cm in length and thereafter declined as the fish predominately fed on marginal vegetation. Scales were used to determine the age of T. rendalli. Age at length data was fitted to the Von Bertalanffy growth model, which showed that males grew faster and attained a larger size than females. The growth of T. rendalli in Flag Boshielo Dam was comparable to those reported in other dams with macrophytes. It is inferred here that the absence of macrophytes is not a limiting factor in the growth of T. rendalli in lentic ecosystems. The ability of T. rendalli to achieve good growth rates when feeding on marginal vegetation prompted a subsequent study where its utilisation of readily available plant diets was evaluated under culture conditions. The culture of macrophagous fish that naturally feed on plant diets may be the solution to reduce the current dependence on fishmeal. Fishmeal is not only expensive, but its supply is not always guaranteed. This study focussed on the growth performance, gastric evacuation rate, gastric transit time and carcass composition of Tilapia rendalli fed fresh plants, to determine the extent to which T. rendalli can utilise fresh plants. Kikuyu grass (Pennisetum clandestinum), cabbage (Brassica oleracea), duckweed (Lemna minor), vallisneria (Vallisneria aethiopica) and fishmeal pellets (control) were offered ad libitum to duplicate groups of T. rendalli for 224 days. Specific growth rate (SGR), protein efficiency ratio (PER) and food conversion ratio (FCR) were used to determine the growth performance. Fish fed kikuyu grass attained a significantly (P<0.05) higher SGR and a better FCR than those fed on the other plant diets. Fish fed vallisneria lost weight. The serial slaughter method showed that vallisneria was vii evacuated significantly (P<0.05, ANCOVA) faster and was eaten in significantly (P<0.05) higher quantities than the other diets. Kikuyu grass was evacuated much more slowly and eaten in lesser amounts than the other plant diets. The low energy content (14.74 MJ/kg) of vallisneria may explain its faster evacuation and high consumption levels. Digestibility studies indicated that T. rendalli is capable of breaking down both cellulose and fibre. Fish fed kikuyu grass had higher protein levels, higher omega-3 fatty acids (25.13%) and higher mineral content than those fed on the other experimental diets. Fishmeal fed fish had the lowest content of the omega-3 fatty acids (2.52%). T. rendalli performed better when fed plant diets with higher protein and energy contents. The good growth performance and carcass quality of T. rendalli fed on kikuyu grass, led to another study where the use of kikuyu grass meal as a dietary protein replacement for fishmeal in practical diets for T. rendalli was evaluated. To determine the optimum substitution level, kikuyu grass meal was used to replace 20, 40, 60 and 80% of fishmeal in isonitrogenous (CP =16.70%) and isocaloric (GE =15.20 MJ/kg) diets. The test diets were fed to triplicate groups of fish held in 1 m3 fibre glass tanks at 10 (36 ± 2 g) fish per tank for 60 days. The best specific growth rate (1.60 g/day) and feed conversion ratio (1.86) were recorded for fish fed diets with 20% kikuyu grass meal. The lowest specific growth rate (1.29 g/day) and feed conversion ratio (2.56) were recorded for fish fed diets with 80% kikuyu grass meal. When the level of kikuyu grass meal was more than 20% in the diet, growth performance was reduced. However, there were no statistically significant differences in the growth performance indices measured across the tested diets. The observed reduction in growth for diets containing higher kikuyu grass meal is explained by the decreasing amino acids levels (particularly methionine and lysine) and increasing fibre content. The results from the growth trials suggest that kikuyu grass meal is a suitable protein replacement for the expensive fishmeal in T. rendalli practical diets when it constitutes up to 20% of the dietary protein.

In order to investigate the interactions of dietary protein and energy and their utilisation by African catfish, Clarias gariepinus (Burchell, 1822) (12.43 ± 0.05 g), a series of four nutritional experiments (triplicate groups of 20 fish per 30-L tank at 28 ± 1°C, for 8 weeks) were carried out using fish meal based diets. Optimum dietary protein to energy ratio (P/E ratio) and optimum lipid to carbohydrate ratio (L/CHO ratio) were investigated. Based on optimised dietary P/E ratio and L/CHO ratio, optimum feeding regime and compensatory growth were also investigated in this species. In the experiments to optimise P/E ratio and L/CHO ratio fish were offered each diet at 5% of their body weight per day adjusted fortnightly. In the optimum feeding regime experiments, fish were offered each diet to appetite or to a restricted level. The restricted regimes were achieved by offering fish decreasing fixed feeding rates with increasing dietary protein level. Studies on compensatory growth were conducted in two phases each of 4 weeks. In the first phase, triplicate groups of 30 fish and in the second phase triplicate groups of 20 fish (per 30-L tank) were offered the diet in six mixed feeding schedules at two feeding regimes i.e. appetite and restricted. The restricted regime was achieved by offering fish 1% (maintenance ration) of their body weight per day adjusted after fortnightly weighing. Optimum dietary P/E and L/CHO ratios were 20.54-mg protein/kJ of GE and 0.40 g/g respectively, with a crude protein level over 40% and gross energy of more than 20 kJ/g GE. The results of investigating feeding regimes suggest that dietary protein level could be reduced from over 40% to 35% by feeding to appetite based on the above optimised dietary P/E and L/CHO ratios. Addition of dietary energy as lipid at varying protein levels resulted in increased growth, protein and energy utilisation in C. gariepinus. Based on optimised dietary P/E ratio, dietary carbohydrate levels were increased (with concomitant reduction in dietary lipid levels) resulting in a trend towards higher growth performance, protein and energy utilisation. Protein and energy utilisation did not vary (P > 0.05) with feeding regime or dietary protein level. C. gariepinus showed partial compensatory growth under alternating periods of feeding a restricted (maintenance requirements) and appetite ration and also showed higher feed, protein, lipid and energy utilisation efficiencies in comparison to appetite feeding.Increase in dietary lipid produced an increment in carcass lipid deposition, both in whole body and liver in all studies. Fish in all treatments did not show significant differences (P < 0.05) in body protein content. Optimum P/E ratio studies, with varying dietary protein and energy level, produced higher liver glycogen, plasma glucose and plasma triglycerides at higher dietary carbohydrate level with lower protein diets. In the studies to optimise lipid to CHO ratio comparatively lower (P < 0.05) plasma glucose and plasma cholesterol deposition were observed while no consistent trends were found in liver glycogen deposition in fish fed higher dietary lipid with concomitant lower CHO levels. Studies on optimising feeding regime, with varying protein levels, did not show any significant differences (P < 0.05) in liver glycogen, plasma glucose, plasma triglycerides and plasma cholesterol in response to dietary treatment. In all studies fish fed the experimental diets showed insignificant differences (P > 0.05) in plasma amino acid levels and digestive enzyme activities (protease and lipase) while intestinal a-amylase activity increased with increasing dietary carbohydrate level. Histological examination of intestine & liver in all studies showed no abnormalities. In conclusion, these studies suggest that manipulation and optimisation of dietary protein and energy intakes plays a very significant role in African catfish, Clarias gariepinus nutrition.

Made available in DSpace on 2015-03-03T11:52:53Z (GMT). No. of bitstreams: 0 Previous issue date: 2014-03-12Bitstream added on 2015-03-03T12:06:55Z : No. of bitstreams: 1 000809753.pdf: 636196 bytes, checksum: 431eaf1039593922667938e3e9f16f39 (MD5) / A adequada utilização de carboidratos nas dietas de peixes carnívoros pode reduzir a utilização da fração proteica da dieta para fins energéticos, aumentando sua utilização para o crescimento, num processo conhecido como protein sparing. A anatomia e histologia do sistema digestório dos surubins demonstram que os mesmos possuem particularidades próximas a de onívoros que poderiam ajudar no aproveitamento de carboidratos da dieta. O metabolismo de carboidratos nos peixes parece ter inúmeras contradições e pode variar em função da espécie, fonte e processamento do carboidrato e níveis de inclusão na dieta. Alguns estudos demonstram que surubins conseguem digerir e utilizar os amidos fornecidos nas dietas, ocasionando adaptações fisiológicas na secreção de enzimas digestivas e metabólicas. Não existem estudos específicos em relação à utilização de carboidratos com efeito poupador de proteína para surubins, porém a utilização de lipídeos com efeito poupador já foi estudada, não resultando em melhora no desempenho produtivo dos peixes. Devido à carência de estudos para espécies nativas em geral, o presente trabalho verificou a influência de níveis de carboidratos e proteína nas dietas de cacharas. Os índices zootécnicos, metabolismo, reservas energéticas, composição e retenção de nutrientes na carcaça e quantificação de enzimas digestivas foram avaliados. Pode-se concluir que o aumento do nível de carboidratos não resultou em efeito poupador de proteína para o surubim / The proper use of carbohydrates in diets for carnivorous fish can reduce the use of the protein fraction for energy, providing its for growth, a process known as protein sparing. The anatomy and histology of digestive system of surubins demonstrate that they possess characteristics similar to omnivores fish that could help on the carbohydrates utilization. Carbohydrate metabolism in fish seems to have many contradictions and vary depending on fish specie, carbohydrates sources and processing and carbohydrate inclusion level. Some studies showed that surubins can digest and utilize dietary starch, resulting in physiological adaptations, such as digestive enzymes secretion. There are no specific studies on the use of carbohydrates with protein sparing effects for surubins, but the use of lipids has been studied, resulting in no improvement in growth performance of fish. Due to the lack of studies to native species in general, the present study examined the influence of different levels of carbohydrate and protein in the diets of cacharas. Production indices, metabolism, energy reserves, composition and nutrient retention in the carcass and quantification of digestive enzymes were evaluated. It can be concluded that increasing the carbohydrate level has not resulted in a protein-sparing effect for the surubim

Made available in DSpace on 2014-06-11T19:26:01Z (GMT). No. of bitstreams: 0 Previous issue date: 2012-06-01Bitstream added on 2014-06-13T19:53:53Z : No. of bitstreams: 1 rocha_mkhr_me_botfmvz.pdf: 206056 bytes, checksum: b4220d7b33a179c4a5950580e30d0d86 (MD5) / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES) / Universidade Estadual Paulista (UNESP) / Os objetivos desta pesquisa foram avaliar a quantidade de fósforo disponível presente em rações experimentais e por meio delas determinar a exigência do mineral para adequada mineralização óssea de alevinos da tilápia do Nilo. Foram formuladas quatro dietas para conter níveis de 2,0; 4,0 e 6,0g kg-1 de fósforo disponível utilizando-se fosfato bicálcico e uma dieta sem suplementação (1,5g kg-1). Todas acrescidas de 1,0g kg-1 de Cr2O3. Para a determinação do coeficiente de disponibilidade do fósforo foram distribuídos 160 peixes (peso médio de 30g + 0,5) em oito aquários, alimentados com as dietas experimentais para coleta de fezes. A exigência de fósforo foi avaliada utilizando grupos de peixes com peso inicial médio de 1,2g + 0,5; sendo alimentados quatro vezes ao dia durante 90 dias até a saciedade aparente. Foram avaliados sobrevivência, ganho de peso, porcentagem de cálcio e fósforo presentes nas vértebras, concentração de fósforo presente na água, densitometria óssea (vértebras e corpo) e imagens tomográficas. As melhores respostas apresentadas pelos peixes foram entre 4,0 e 6,0g kg-1 de fósforo disponível nas dietas / The aim of this study were to evaluate the amount of present available phosphorus in the experimental diets and through them to determine minimum requirement of the mineral for proper bone mineralization of Nile tilapia fingerlings. Four diets were formulated to contain levels of 2.0, 4.0 and 6.0 g kg-1 available phosphorus by calcium phosphate and a diet without supplementation (1.5 g kg-1). All diets were added 1,0g kg-1 Cr2O3. To determine the coefficient of phosphorus availability were distributed 160 fish (average weight 30g + 0.5) in eight tanks, fed the experimental diets for feces. The requirement of phosphorus was evaluated in fish with initial average weight of 1.2g+ 0.5, being fed four times daily for 90 days until satiation. Were evaluated survival, weight gain, percentage of calcium and phosphorus in the vertebrae, phosphorus concentration in the water, bone densitometry (vertebrae and body) and tomography images. The best responses were submitted by the fish between 4.0 and 6.0 g kg-1 of available phosphorus in the diets

Orientador: Leonardo Susumu Takahashi / Banca: Urbano dos Santos Ruiz / Banca: João Batista Kochenborger Fernandes / Resumo: A adequada utilização de carboidratos nas dietas de peixes carnívoros pode reduzir a utilização da fração proteica da dieta para fins energéticos, aumentando sua utilização para o crescimento, num processo conhecido como "protein sparing". A anatomia e histologia do sistema digestório dos surubins demonstram que os mesmos possuem particularidades próximas a de onívoros que poderiam ajudar no aproveitamento de carboidratos da dieta. O metabolismo de carboidratos nos peixes parece ter inúmeras contradições e pode variar em função da espécie, fonte e processamento do carboidrato e níveis de inclusão na dieta. Alguns estudos demonstram que surubins conseguem digerir e utilizar os amidos fornecidos nas dietas, ocasionando adaptações fisiológicas na secreção de enzimas digestivas e metabólicas. Não existem estudos específicos em relação à utilização de carboidratos com efeito poupador de proteína para surubins, porém a utilização de lipídeos com efeito poupador já foi estudada, não resultando em melhora no desempenho produtivo dos peixes. Devido à carência de estudos para espécies nativas em geral, o presente trabalho verificou a influência de níveis de carboidratos e proteína nas dietas de cacharas. Os índices zootécnicos, metabolismo, reservas energéticas, composição e retenção de nutrientes na carcaça e quantificação de enzimas digestivas foram avaliados. Pode-se concluir que o aumento do nível de carboidratos não resultou em efeito poupador de proteína para o surubim / Abstract: The proper use of carbohydrates in diets for carnivorous fish can reduce the use of the protein fraction for energy, providing its for growth, a process known as "protein sparing". The anatomy and histology of digestive system of surubins demonstrate that they possess characteristics similar to omnivores fish that could help on the carbohydrates utilization. Carbohydrate metabolism in fish seems to have many contradictions and vary depending on fish specie, carbohydrates sources and processing and carbohydrate inclusion level. Some studies showed that surubins can digest and utilize dietary starch, resulting in physiological adaptations, such as digestive enzymes secretion. There are no specific studies on the use of carbohydrates with protein sparing effects for surubins, but the use of lipids has been studied, resulting in no improvement in growth performance of fish. Due to the lack of studies to native species in general, the present study examined the influence of different levels of carbohydrate and protein in the diets of cacharas. Production indices, metabolism, energy reserves, composition and nutrient retention in the carcass and quantification of digestive enzymes were evaluated. It can be concluded that increasing the carbohydrate level has not resulted in a protein-sparing effect for the surubim / Mestre

Orientador: Luiz Edivaldo Pezzato / Coorientador: Edma Miranda de Carvalho / Banca: Hamilton Hisano / Banca: Vânia Vasconcelos / Resumo: Os objetivos desta pesquisa foram avaliar a quantidade de fósforo disponível presente em rações experimentais e por meio delas determinar a exigência do mineral para adequada mineralização óssea de alevinos da tilápia do Nilo. Foram formuladas quatro dietas para conter níveis de 2,0; 4,0 e 6,0g kg-1 de fósforo disponível utilizando-se fosfato bicálcico e uma dieta sem suplementação (1,5g kg-1). Todas acrescidas de 1,0g kg-1 de Cr2O3. Para a determinação do coeficiente de disponibilidade do fósforo foram distribuídos 160 peixes (peso médio de 30g + 0,5) em oito aquários, alimentados com as dietas experimentais para coleta de fezes. A exigência de fósforo foi avaliada utilizando grupos de peixes com peso inicial médio de 1,2g + 0,5; sendo alimentados quatro vezes ao dia durante 90 dias até a saciedade aparente. Foram avaliados sobrevivência, ganho de peso, porcentagem de cálcio e fósforo presentes nas vértebras, concentração de fósforo presente na água, densitometria óssea (vértebras e corpo) e imagens tomográficas. As melhores respostas apresentadas pelos peixes foram entre 4,0 e 6,0g kg-1 de fósforo disponível nas dietas / Abstract: The aim of this study were to evaluate the amount of present available phosphorus in the experimental diets and through them to determine minimum requirement of the mineral for proper bone mineralization of Nile tilapia fingerlings. Four diets were formulated to contain levels of 2.0, 4.0 and 6.0 g kg-1 available phosphorus by calcium phosphate and a diet without supplementation (1.5 g kg-1). All diets were added 1,0g kg-1 Cr2O3. To determine the coefficient of phosphorus availability were distributed 160 fish (average weight 30g + 0.5) in eight tanks, fed the experimental diets for feces. The requirement of phosphorus was evaluated in fish with initial average weight of 1.2g+ 0.5, being fed four times daily for 90 days until satiation. Were evaluated survival, weight gain, percentage of calcium and phosphorus in the vertebrae, phosphorus concentration in the water, bone densitometry (vertebrae and body) and tomography images. The best responses were submitted by the fish between 4.0 and 6.0 g kg-1 of available phosphorus in the diets / Mestre

This research reports on the determination of the effects of fish size and feed pellet size on the settling characteristics of Rainbow trout (Salmo gairdneri) culture, tank cleaning wastes. Flocculant particle settling curves (Type II) were developed from settling column analysis of cleaning wastes from 11-311 gram Rainbow trout fed a moist pellet diet (Oregon Moist Pellet ®). Four feed pellet sizes were investigated: 3/32, 1/8, 5/32 and 3/16 inch. Overall non-filterable residue removal curves and individual particle settling velocity distribution curves, derived from the Type II settling curve of each fish size and feed pellet size group, were compared. Slopes and y-intercepts of the linearized overall non-filterable residue removal curves and individual particle settling velocity distribution curves were compared using the Equality of Slope Test (S:SLTEST). Results of the test for a common regression equation indicated there were no significant differences in the proportional distribution of particle sizes within the cleaning wastes. Variations observed in the initial rates of removal within the overall non-filterable residue removal curves were considered insignificant Settling trials were pooled in order to obtain single curves, characterizing the overall solids removal rate and the individual particle settling velocity distribution of the waste solids. / Applied Science, Faculty of / Chemical and Biological Engineering, Department of / Graduate

A two year study was initiated in 1973 to examine effects of substantial (3.8 fold; from a 1962-66 mean of 39 million to about 150 million in 1973 and 1974) increases in sockeye (Oncorhynchus nerka) Walbaum) fry numbers on zooplankton abundance in Babine Lake. Several lake areas and stationsware sampled for zooplankton bimonthly from May to October during 1973 and 1974 and compared to data gathered between 1958 and 1962 prior to a large scale enhancement program for sockeye stocks. Zooplankton biomass had decreased up to 70% in some areas of the lake during 1973, but only 40% in 1974. Decreases in numbers were also evident. Although seasonal changes in fry diet followed changes in zooplankton species abundance, feeding was selective. The less abundant but larger forms, Daphnia and Heterocope together comprised 70% of the diet during summer, while Cyclops and Diaptomus formed the bulk (87%) of the diet in late fall. Significant decreases in Daphnia and Diaptomus abundance and increases in nauplii-early copepodite abundance had occurred by 1973. The increased 1974 zooplankton abundance relative to 1973 was attributed to decreased mid-summer fry numbers in the lake. Field data suggested low Diaptomus numbers contributed to much higher fry mortality (about double in 1974) compared to 1973. An experimental study of species selectivity by sockeye fry indicated that they selected Cyclops and Diaptomus adults. The larger copepods, Heterocope and Epischura, were rejected by fry encountering zooplankton for the first time. Copepodites and nauplii were rejected, but less so when preferred prey were scarce. Prey activity, in my experiments, could not be used to predict predation vulnerability and hence the species selectivity displayed by the fry. Light and temperature had little effect on Cyclops, Dlaptomus and Heterocope activity. / Science, Faculty of / Zoology, Department of / Graduate

This study was conducted to satisfy three objectives. The first was to provide a detailed description of the differences between the prey contents of rainbow trout (Salmo qairdneri) and kokanee (Oncorhynchus nerka) compared either to each other or to the prey contents of the natural environment. The second was to determine how elements of anatomy, physiology and behaviour interact to promote the acquisition of species specific diets by trout and kokanee. The third was to precisely identify the foraging strategies of the two predators by assessing how different anatomical and behavioural characteristics serve as interrelated adaptations that suit each species to effectively use a specific habitat-prey complex. Matched samples of trout and kokanee from Marion Lake exhibit only modest A dietary overlap (mean of C λ = .462, range.136 to .881). Although kokanee appear to track the environmental abundance of prey more closely than trout, both predators exhibit pronounced patterns of "density independent" acquisition of prey from the total complex of prey that is apparently available in the lake. To test hypotheses about the factors that control these dietary patterns, I conducted a series of studies concerning where trout and kokanee choose to forage, when they choose to forage, how they search for prey, how they attack prey, and how experience in encountering various prey alters the predator's foraging behaviour. Temporal segregation of trout and kokanee foraging activities is not well-developed under field conditions and appears unlikely to promote strong patterns of food-resource partitioning. By contrast, spatial segregation is well-developed and clearly plays a major role in promoting the acquisition of relatively large numbers of nearshore benthic prey ( eg. planorbid snails or odonates ) by trout and of relatively large numbers of offshore, water-column prey ( eg. chironomid pupae ) by kokanee. Close inspection of the details of predator and prey distributions indicates that many aspects of food-resource partitioning are not logical outcomes of spatial segregation. Differences in predator search-techniques do not determine the presence or absence of various prey types in predator diets, however, differences in predator search behaviours do bias them to obtain different quantities of particular classes of prey. Kokanee search procedures allow them to detect prey in both exposed and concealed locations while trout detect only exposed prey. While searching for benthic or lake-surface prey, kokanee maintain search positions which allow them to detect prey of smaller sizes than trout. This clearly favours the trend for kokanee to include greater quantities of small prey (eg. Hyalella sp.) in their diets than trout. Differences in search procedures do not explain why kokanee obtain a greater proportion of their diet than trout from small zooplankton (≤ 1 mm ) in late summer or why kokanee seldom exploit any of the relatively large ( > 4 mm ), armoured prey that are common in the diet of similar sized trout. Differences in both behavioural and morphological characteristics involved in the attack phase of foraging by trout and kokanee serve as the basis for explanations of a number of differences between the diets of free-ranging predators. These differences include: the greater utilization of aerial prey by trout, the inclusion of large numbers of copepods in the diet of kokanee but not of trout, the generally greater utilization of zooplankton by kokanee compared to trout, and the relative-scarcity of large ( > 4 mm ), armoured prey, in the diet of kokanee. A series of laboratory experiments was used to examine the extent to which short term experience might influence food-resource partitioning by trout and kokanee. These experiments offered convincing evidence that differential effects of experience will amplify the trends in resource partitioning already set in motion by differences in habitat selection, search procedures, and attack procedures. I argue that the morphological and behavioural traits that control food "selection" by trout and kokanee in Marion Lake are a consequence of the evolution of mutually exclusive foraging strategies. Trout are portrayed as D-strategists that concentrate on relatively large, dispersed prey for the bulk of their energy requirements. Adaptations which enable trout to differentially exploit large prey include: procedures for area-extensive search; a predisposition to attack relatively large, armoured-prey; large mouth-size; and persistent responses to opportunities to attack large prey. An inability to sustain high attack rates on small prey ( < 1 mm ) at high density ( 35 per liter ) and a tendency to ignore or reject such prey suggest that trout are not well-adapted to exploit relatively small, morphologically-uniform,prey. Kokanee are portrayed as C-strategists which concentrate on relatively small, contagiously-distributed prey for the bulk of their energy requirements. Adaptations which enable kokanee to differentially exploit small prey include: procedures for area-intensive search; a predisposition to attack relatively small, morphologically-uniform prey; small mouth-size; well-developed gill-rakers; and an ability to sustain high attack rates on small planktonic prey. Low ingestion success with a variety of large benthic prey and a tendency to ignore or reject such prey under laboratory conditions where they serve as the sole source of food are evidence that kokanee are not well adapted to exploit large, armoured-prey. Adaptations associated with the search, capture, manipulation and ingestion phases of the foraging cycle appear in each instance to be evolutionary responses to specific features of a given habitat-prey complex. C-selected or D-selected foraging strategies appear to be mutually exclusive evolutionary avenues down which trout and kokanee have been directed by the fundamental nature of a given habitat-prey complex. / Science, Faculty of / Zoology, Department of / Graduate