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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
41

Life along the Kenepocomoco : archaeological resources of the upper Eel River Valley

Richey, Kristine Diane January 1994 (has links)
An archaeological survey documenting sites along Upper Eel River within the Indiana counties of Allen, Whitley, Kosciusko and Wabash was conducted during 199192 to collect data which was analyzed to provide a clearer understanding of the region's cultural chronology and describe the area's cultural resources. A total of 765 previously unrecorded sites were documented, 493 of which were field-checked during field reconnaissance of 10% of the project universe, with 1010.82 acres surveyed. A research project completed entirely by volunteers succeeded in locating a number of potential archaeological sites from the Historic Period.Data from the present study securely defined the cultural chronology of the Upper Eel River Valley and yielded valuable information concerning settlement patterns, ecological exploitation, and avenues of migration. Cultural sequencing revealed the presence of Early Paleo-Indians along the river valley at approximately 12,000 B.P. and chronicled the continued expansion of prehistoric populations within the area into historic times. / Department of Anthropology
42

Immobilisation of electric eel acetylcholinesterase on nanofibres electrospun from a nylon and chitosan blend

Mafuma, Tendai Simbarashe January 2013 (has links)
Organophosphates and carbamates are potent inhibitors of the neurotransmitter acetylcholinesterase. This inhibition results in the blocking of nerve signal transference into the post synaptic neuron leading to loss of muscle action and death. Because of the universal mechanisms of signal transduction in animals, these inhibitors have been widely used as agricultural pesticides as well as chemical warfare agents (nerve agents). Health issues associated with pesticide usage result from the fact that both the pesticides and their breakdown products often end up in water and food sources as well as in the soil. As a result, there has been an increase in the number of studies aimed at the detection of these pesticides in the environment. One popular research area is enzyme based biosensor construction. Some important criteria for consideration during the construction of biosensors are the importance of a suitable solid support as well as the enzyme immobilisation method. Recently, there has been increased interest in using nano-scale material e.g. using nanoparticles as enzyme support material. This is largely due to their advantages such as large surface area to volume ratio as well as reduced mass transfer resistance. Electrospinning is a straight forward and cost effective method for producing nanofibres from any soluble polymer(s). The applications of electrospun nanofibres have been reported in clinical studies, biofuel production as well as bioremediation. In this study two polymers were selected: nylon for its mechanical stability and chitosan for its biocompatibility and hydrophilicity, for the fabrication of electrospun nanofibres which would function as immobilisation support material for acetylcholinesterase. The first objective of this study was to electrospin nanofibres from a nylon-6 and chitosan blend solution. A binary solvent system consisting of formic acid and acetic acid (50:50) successfully dissolved and blended the polymers which were subsequently electrospun. Scanning electron microscopy characterisation of the nanofibres showed that (i) a nylon-6: chitosan ratio of 16%: 3% resulted in the formation of bead free nanofibres and (ii) the fibres were collected in non-woven mats characterised by different size nanofibres with average diameters of 250 nm for the main fibres and 40 nm for the smaller nanofibres. Fourier transform infra-red (FT-IR) analysis of the nanofibres indicated that a new product had been formed during the blending of the two polymers. The second aim of the study was to carry out a facile immobilisation of electric eel acetylcholinesterase via glutaraldehyde (GA) cross-linking. Glutaraldehyde solution 5% (v/v) resulted in the immobilisation of 0.334 mg/cm² of acetylcholinesterase onto the nanofibres. The immobilisation procedure was optimised with reference to acetylcholinestease and crosslinker concentrations, incubation time and the cross-linking method. A comparative investigation into the optimum pH and temperature conditions, pH and thermal stabilities, substrate and inhibition kinetics was then carried out on free and immobilised acetylcholinesterase. The final objective of this study was to determine the storage stabilities of the immobilised and free enzymes as well as the reusability characteristics of the immobilised acetylcholinesterase. Several conclusions were drawn from this study. Acetylcholinesterase was successfully immobilised onto the surface of nylon-6:chitosan nanofibres with retention of its activity. There was a shift in the pH optimum of the immobilised acetylcholineseterase by 0.5 units towards a neutral pH. Although both free and immobilised acetylcholinesterase exhibited the same optimum temperature, immobilised acetylcholinesterase showed enhanced thermal stability. In terms of pH stability, immobilised acetylcholinesterase showed greater stability at acidic pH whilst free acetylcholinesterase was more stable under alkaline pH conditions. Relative to free acetylcholinesterase, the immobilised enzyme showed considerable storage stability retaining ~50% of its activity when stored for 49 days at 4°C. Immobilised acetylcholinesterase also retained > 20% of its initial activity after 9 consecutive reuse cycles. When exposed to fixed concentrations of carbofuran or demeton-S-methyl sulfone, immobilised acetylcholinesterase showed similar inhibition characteristics to that of the free enzyme. The decrease in enzyme activity observed after immobilisation to the nanofibres may have been due to several reasons which include some enzyme molecules being immobilised in structural conformations which reduced substrate access to the catalytic site, participation of the catalytic residues in immobilisation and enzyme denaturation due to the reaction conditions used for acetylcholinesterase immobilisation. Similar observations have been widely reported in literature and this is one of the major drawbacks of enzyme immobilisation. In conclusion, nylon-6:chitosan electrospun nanofibres were shown to be suitable supports for facile acetylcholinesterase immobilisation and the immobilised enzyme has potential for use in pesticide detection. Future recommendations for this study include a comparative study of the GA cross-linking method for AChE immobilisation which will lead to more intensely bound enzyme molecules to prevent non-specific binding. An investigation into the effect of inhibitors on stored immobilised AChE, as well as reactivation and reuse studies, may also be useful for determining the cost-effectiveness of reusing immobilised AChE for pesticide detection in environmental water samples. Several models have been designed for the determination of the kinetic parameters for immobilised enzymes. These take into account the mass transfer resistance as well as the overall charge of the immobilisation matrix. The use of these models to analyse experimental data will give a clear understanding of the effects of immobilisation on enzyme activity
43

Sperm physiology and quality in two marine teleosts: Anguilla anguilla & Takifugu niphobles

Gallego Albiach, Victor 20 December 2013 (has links)
The conservation status of the species studied in this thesis (European eel and pufferfish) is currently frail, thus the main goal of this research was to develop, improve and apply several techniques and protocols with the aim of increasing the knowledge about their sperm biology, improving their reproductive performance and even helping future breeding in captivity. The reproductive performance of the males is often assessed through the sperm motion parameters analysed by the CASA system, so first we focused on how to standardize this technique in terms of procedural and biological settings. In this respect, we laid the foundations for applying a standard method to assess sperm quality in fish, making it possible for sperm studies to be compared both intra- and inter-laboratories using the proper CASA settings. Secondly, with the aim of improving the reproductive performance of European eel males, 3 thermal regimes (two of them variable: T10 and T15; and one of them constant: T20) and 3 hormonal treatments (hCG, hCGrec and PSMG) were assessed based on different sperm quality parameters. In the case of the thermal regimes, our results demonstrated that the onset and progression of spermiation are strongly influenced by water temperature, with treatment T20 showing the best results in all the sperm quality parameters. In the case of hormonal treatments, hCGrec produced the best results in all the sperm quality parameters, becoming an economically profitable/viable treatment and an effective alternative to the standard hCG treatment often used to induce spermiation in eel species. A preliminary physiological study regarding the changes to the main ions involved in the fish sperm activation process was carried out. Our results showed that intracellular concentrations of Ca2+ and K+ increased upon eel sperm activation, while pH gradually decreased over time, thus it is likely that all of them play an important role in the initiation of sperm motility in the European eel, as with other marine and freshwater teleosts. In the second part of this thesis, which focuses on the pufferfish, an in-depth study into the sperm of this species was carried out for future application in aquacultural matters. A short-term storage method for pufferfish sperm was developed, enabling us to preserve the sperm quality parameters for a relatively long time period (7 days) compared to fresh sperm samples. Moreover, the effects of both the osmolality and the ion composition of the activation media on the sperm motion parameters were evaluated, concluding that both factors play an essential role in the initiation of sperm motility of pufferfish sperm and probably, in marine fish sperm. Finally, in vitro fertilization trials were developed to assertain how the quantity and quality of male gametes affects the fertilization and hatching rates. We demonstrated that sperm/egg ratio and sperm quality are strongly related factors, suggesting that both should be taken into account as unique interrelated elements. In addition, coefficients of correlation among all the spermatozoa motion parameters provided by a CASA system and fertilization and hatching rates were estimated for the first time in a marine species. Spermatozoa velocities showed the highest coefficients (¿0.80), suggesting that the kinetics of the spermatozoa are a key factor in the fertilization process. / Gallego Albiach, V. (2013). Sperm physiology and quality in two marine teleosts: Anguilla anguilla & Takifugu niphobles [Tesis doctoral]. Universitat Politècnica de València. https://doi.org/10.4995/Thesis/10251/34625 / TESIS / Premios Extraordinarios de tesis doctorales
44

Étude parasitologique de Anguilla anguilla dans deux lagunes de Corse et étude ultrastructurale du tégument de trois digènes parasites de cette anguille / parasitological study of Anguilla Anguilla in two lagoons in Corsica and ultrastructural study of the integument of three digeneans parasites that eel

Filippi, Jean-José 14 March 2013 (has links)
Une étude parasitaire de l'anguille d'Europe a été menée dans les lagunes de Biguglia et d'Urbino en Corse. La composition des communautés de parasites a été décrite. Treize espèces parasites ont été identifiées parmi lesquelles: trois digènes, Bucephalus anguillae, Deropristis inflata, Lecithochirium musculus; un monogène, Pseudodactylogyrus anguillae; trois cestodes, Bothriocephalus claviceps, Proteocephalus macrocephalus, Myzophyllobothrium sp. (larve); trois nématodes, Anguillicoloides crassus, Contracaecum sp. (larve enkystée), Goezia anguillae; un acanthocéphale, Acanthocephaloides incrassatus; un copépode, Ergasilus gibbus; et un myxozoaire, Myxobolus portucalensis. La présence d'espèces invasives, notamment le parasite branchial P. anguillae et le nématode parasite A. crassus, dans les lagunes corses est confirmée. Ces espèces, et particulièrement le monogène, présentent des valeurs épidémiologiques croissantes depuis les dernières études menées. Plusieurs espèces présentent des différences de prévalence significatives entre les deux lagunes. Des différences au niveau de la richesse spécifique et des valeurs de diversité, plus élevées pour les parasites des anguilles de la lagune d'Urbino au niveau intestinal métacommunautaire et infracommunautaire, ont été démontrées. Cependant les valeurs les plus élevées de diversité spécifique et les valeurs de dominance les plus basses ont été calculées pour les communautés parasitaires des anguilles de la lagune de Biguglia. Nous avons également mis en avant une diversité parasitaire spécifique plutôt faible chez les anguilles des lagunes corses par rapport aux autres lagunes d'Europe. Les communautés parasitaires de l'anguille d'Europe dans les lagunes de Biguglia et d'Urbino en Corse sont marquées par l'environnement de leur hôte. Une dépendance vis-à-vis de la salinité de la lagune a ainsi été démontrée. Les valeurs d'infestation les plus élevées ont été observées durant les saisons les plus chaudes de l'année pour la majorité des espèces parasites observées (B. anguillae, D. inflata, L. musculus, P. anguillae, P. macrocephalus, A. crassus, les kystes de Contracaecum sp., A. incrassatus et E. gibbus). Nous avons également démontré que l'état d'argenture et la taille ont une influence significative sur les taux d'infestation de sept espèces parasites (D. inflata, L. musculus, P. anguillae, P. macrocephalus, les kystes de Contracaecum sp., A. incrassatus et E. gibbus). La méthode de l'espèce indicatrice a confirmé que le site d'étude, la saison, l'état d'argenture ou la taille de l'anguille pouvait influer sur la présence de certaines espèces parasites. Le tégument de trois digènes parasites de l'anguille d'Europe, B. anguillae, L. musculus et D. inflata, a été étudié en microscopie électronique à balayage et à transmission. Nous avons démontré la présence de structures caractéristiques de l'organisation tégumentaire des digènes ainsi que de formations spécifiques, notamment au niveau de la structure des récepteurs sensoriels et des écailles. / A survey of the parasitic fauna of the European eel has been conducted in the Biguglia and Urbino lagoons in Corsica. The composition of the parasite communities was determined. Thirteen parasite species were identified namely: three digeneans, Bucephalus anguillae, Deropristis inflata, Lecithochirium musculus; one monogenean, Pseudodactylogyrus anguillae; three cestodes, Bothriocephalus claviceps, Proteocephalus macrocephalus, larvae of Myzophyllobothrium sp.; three nematodes, Anguillicoloides crassus, encysted larvae of Contracaecum sp., Goezia anguillae; one acanthocephalan, Acanthocephaloides incrassatus; one copepod, Ergasilus gibbus; and plasmodia of one myxozoan, Myxobolus portucalensis. The presence of invasive species in lagoons from Corsica, namely the gill monogenean P. anguillae and the swimbladder nematode A. crassus, was confirmed. These species, particularly the monogenean, exhibit increasing infection rates since the last studies conducted. Many species showed significant differences in prevalence between the two lagoons. Differences in the species richness and higher values of diversity for the intestinal parasite component communities and infracommunities of eels from the Urbino lagoon were demonstrated. However, highest values of richness and lowest dominance values were observed for the parasite communities of eels from the Biguglia lagoon. We also demonstrated lower values of diversity for the parasite communities of eels from Corsica in comparison to eels from other European lagoons. The environment of the host (in particular the salinity range) has been demonstrated to have a significant influence on the composition of the parasite communities of eels from the Biguglia and Urbino lagoons. Highest values of infestation were observed for the warmer seasons of the year for the majority of the parasite species (B. anguillae, D. inflata, L. musculus, P. anguillae, P. macrocephalus, A. crassus, encysted larvae of Contracaecum sp., A. incrassatus, and E. gibbus). We also demonstrated that silvering stage and length have a significant influence on the rates of infestation by seven parasite species (D. inflata, L. musculus, P. anguillae, P. macrocephalus, cysts of Contracaecum sp., A. incrassatus et E. gibbus). The indicator species method confirmed the assumption that site sampling, season, silvering stage and length of the eel could have an influence on the presence of parasite species. The teguments of three digeneans (B. anguillae, L. musculus and D. inflata) recovered within the European eel were studied using scanning and transmission electron microscopy. We showed the presence of structures characteristic of the tegumental organization of digeneans but also the presence of specific structures such as various types of sensory receptors and spines.
45

Bubble curtains with vertical tubes : A way to deter fish from hydro power intakes

Molin, Gustav January 2019 (has links)
This project was performed on assigment of Vattenfall R&D in Älvkarleby. The project was a first step in evaluating whether bubble curtains with vertical tubes could be suitable for diverting fish from hydro power intakes into fish passages. To determine this, prototypes were constructed, where one was tested in still water and one in running water. The tests in still water were carried out in a large cylindrical tank and the tests in running water were carried out in Kungsr¨annan in ¨Alvkarleby. A number of test variables were developed to be able to vary the tests. These test variables were hole size, number of holes, tube center-to-center distance, air flow and water velocity. The tests were carried out without fish, but a number of indicators were developed to be able to compare and evaluate the tests. For the tests in still water, these indicators were the width of the bubble curtain created by a single tube and the horizontal movement of the air bubbles, to determine whether the hydrostatic pressure from the surrounding water had any effect on the appearance of the bubble curtain. For the tests in running water, the indicators were the bubble curtain density, the curvature of the tubes and the movement of the tubes. All experiments were documented using cameras and the results were then obtained through image processing in the software MATLAB. The results showed that the width of the bubble curtain created by a single tube varied between 12 and 34 cm for pressures between 0.5 and 2.0 bar. It was concluded that the hydrostatic pressure was of minimal significance for the appearance of the bubble curtain, at least for depths up to 1.95 m. For the tests in running water, the air flow rate and tube center-to-center distance was of the greatest importance for the bubble curtain density. The curvature of the tubes were most affected by the size of the holes and the movement of the tubes were most affected by the number of holes. / Detta projekt utfördes på uppdrag av Vattenfall R&D i Älvkarleby. Projektet var ett första steg i att utvärdera om bubbelridåer med vertikala slangar skulle kunna lämpa sig för att avleda fisk från vattenkraftverk vidare mot fiskpassager. För att avgöra detta konstruerades prototyper, där en testades i stilla vatten och en i rinnande vatten. Testerna i stilla vatten utfördes i en stor cylindrisk tank och testerna i rinnande vatten utfördes i Kungsrännan i Älvkarleby. Ett antal testvariabler togs fram för att kunna variera testerna. Dessa testvariabler var hålstorlek, antal hål, avstånd mellan slangarnas centrum, luftflöde samt vattenhastighet. Testerna gjordes utan fisk, men ett antal indikatorer togs fram för att kunna jämföra och utvärdera testerna. För testerna i stilla vatten var dessa indikatorer bubbelridåns bredd skapad av en enskild slang samt luftbubblornas horisontella förflyttning, för att avgöra om det hydrostatiska trycket från omgivande vattnet hade någon effekt på bubbelridåns utseende. För testerna i rinnande vatten var indikatorerna bubbelridåns täthet, slangens krökning samt slangens rörelser. Alla experiment dokumenterades med hjälp av kameror och resultaten togs sedan fram genom bildhantering i programvaran MATLAB. Resultaten visade att bubbelridåns bredd skapad av en enskild slang varierade mellan 12 och 34 cm för tryck mellan 0,5 och 2,0 bar. Det bedömdes att det hydrostatiska trycket var av minimal betydelse för bubbelridåns utseende, åtminstone för djup upp till 1,95 m. För testerna i rinnande vatten visade resultaten att luftflödet och avståndet mellan slangarnas centrum var av störst betydelse förr bubbelridåns täthet. Slangens krökning påverkades mest av hålens storlek och slangens rörelser påverkades mest av antalet hål.
46

Fonction mitochondriale et espèces réactives dérivées de l'oxygène : effets du genre et de l'entraînement en endurance chez le rat Wistar et l'anguille européenne / Mitochondrial function and reactive oxygen species : effects of gender and endurance training in Wistar rat and European eel

Farhat, Firas 20 March 2015 (has links)
La mitochondrie est le siège principal de la production d’énergie sous forme d’ATP en conditions aérobies, mais aussi d’espèces réactives dérivées de l’oxygène (ROS). La fonction mitochondriale est étroitement liée à la production de ROS puisque ces derniers, selon leur taux, peuvent altérer ou optimiser le rendement énergétique. La plasticité structurale et fonctionnelle de la mitochondrie est essentielle au maintien de l’homéostasie dans toute situation qui nécessite des ajustements métaboliques comme l’exercice physique. Les mécanismes adaptatifs de la fonction mitochondriale et des ROS lors de l’entrainement sont encore loin d’être élucidés ainsi que l’impact du genre sur ces réponses. Dans cette perspective, deux modèles animaux (rat Wistar et anguille européenne) ont été choisis. Les effets d’un entrainement en endurance de même intensité (70% de la vitesse maximale aérobie de course ou de nage) ont été étudiés chez le rat Wistar et l’anguille européenne argentée. Cette dernière est une espèce endurante capable d’effectuer une migration de reproduction de 6000 km et caractérisée par un dimorphisme sexuel de taille. Des mesures in vitro de la consommation d’oxygène, la production radicalaire et d’ATP ont été effectuées simultanément à partir de fibres perméabilisées de cœur et de muscle squelettique. La vulnérabilité ou résistance de la fonction mitochondriale à l’exposition à un système générateur de ROS (mimant un stress oxydant) a également été étudiée. Avant entrainement, chez le rat Wistar, la femelle présente une fonction mitochondriale plus efficiente énergétiquement et plus résistante aux ROS, alors que chez l’anguille, ce profil métabolique et radicalaire est plutôt observé chez le mâle. Après entrainement, quelle que soit l’espèce, la meilleure performance physique observée s’accompagne de modifications métaboliques et radicalaires différentes selon le genre et l’espèce. Chez le rat, l’amélioration de la fonction mitochondriale se traduit différemment selon le sexe. Chez le mâle, l’entrainement induit une amélioration du rendement énergétique via un meilleur couplage entre oxydation et phosphorylation et/ou une meilleure utilisation des électrons au niveau de la chaine respiratoire. Chez la femelle, l’augmentation de la production d’ATP serait liée à l’augmentation de la consommation d’oxygène mitochondriale. Comme chez le rat, l’entraînement induit globalement chez l’anguille une amélioration du rendement énergétique et de la résistance de la fonction mitochondriale aux ROS, mais uniquement chez le mâle. L’ensemble de ces résultats montre des réponses métaboliques et radicalaires dépendantes du genre. Quelle que soit l’espèce, l’entrainement semble être chez le mâle plus bénéfique que chez la femelle en termes d’efficacité énergétique mitochondriale et de résistance de la fonction mitochondriale à un stress oxydant. Dans le contexte de la migration de l’anguille, ces adaptations permettraient au mâle, largement plus petit que la femelle, une efficacité de nage supérieure, permettant leur synchronisation d’arrivée sur le lieu de reproduction. Les similitudes interspécifiques de réponse à l’entraînement selon le genre confortent l’intérêt d’utilisation du modèle poisson dans le champ de la physiologie de l’exercice. / Mitochondrion is the main site of aerobic energy (ATP) and reactive oxygen species (ROS) productions. Mitochondrial function is closely linked to ROS, which, according their rate, can alter or optimize energy efficiency. Structural and functional plasticity of mitochondria is essential to maintain homeostasis in any situation that requires metabolic adjustments as physical exercise. The adaptive mechanisms of mitochondrial function and ROS during training and the impact of gender on these responses are still far from being solved. In this perspective, two animal models (Wistar rat and European eel) were chosen.The effects of endurance training of the same intensity (70% of maximal aerobic speed running or swimming) were studied in Wistar rat and silver European eel. The latter is an enduring species capable of performing a spawning migration of 6000 km and characterized by sexual dimorphism in size. In vitro measurements of oxygen consumption, free radical and ATP productions were carried out simultaneously from heart and skeletal muscle permeabilized fibers. The vulnerability or resistance of the mitochondrial function to a ROS generating system exposure (mimicking oxidative stress) was also studied.Before training, in rat, female has a mitochondrial function energetically more efficient and more resistant to ROS, whereas in eel, this metabolic and radical profile is observed rather in male. After training, whatever the species, the improved physical performance observed is associated with various metabolic and radical changes which depending on gender and species. In rats, the improving of mitochondrial function translates differently according to gender. In male, training induces improvement in energy efficiency through a better coupling between oxidation and phosphorylation and/or better use of electrons at the respiratory chain level. In female, increasing in ATP production may be related to the increase in mitochondrial oxygen consumption. As in rats, training induces globally in eel an improvement in energy efficiency and resistance of mitochondrial function to ROS, but only in male. All these results show metabolic and radical responses depending on gender. Whatever the species, training seems to be most beneficial in males than in females in terms of mitochondrial energy efficiency and resistance of mitochondrial function to oxidative stress. In the context of eel migration, these adaptations allow to male, largely smaller than female, a higher swim efficiency, allowing their synchronization on breeding site. Interspecific similarities in training response by gender confirm the interest of fish model’s using in the field of exercise physiology.
47

Effects of Great Cormorant Predation on Fish Populations and Fishery

Engström, Henri January 2001 (has links)
<p>The strong increase in number of Great cormorants <i>Phalacrocorax carbo</i> in Sweden in recent years has led to conflicts - particularly with fishery. This thesis focuses on the possible effects of cormorant predation on fish populations. In total, data from 15 lakes in South Sweden were included in this study while most studies were carried out in Lake Ymsen. The results suggest that the impact of cormorant predation on natural fish populations was small, and I observed no decline in fish mass after cormorants established. Cormorant predation on eel was difficult to evaluate because of several confounding factors.</p><p>Ruffe, roach and perch were the most important prey species to the cormorants and most fish taken were small. Cormorants do not seem to catch species and sizes in proportion to their occurrence in the fish community.</p><p>Total fish removal by cormorants varied considerably among lakes (0.2-15.0 kg/ha) and cormorant population sizes at the different lakes were significantly positively correlated with fishery catches, which in turn was significantly positively correlated with total phosphorous levels. Thus, cormorant densities in lakes, and perhaps elsewhere, seem to be governed chiefly by fish densities. The fact that cormorant predation appears not to reduce fish densities suggest cormorants to be regulated by other means than prey depletion. The mechanism behind population regulation could be a behavioural response of fish, making fish more difficult to catch for the cormorants.</p><p>In recent years, cormorant populations have been subjected to intensive legal and illegal actions with the aim to reduce cormorant numbers. However, the actions currently carried are well below the efforts needed to limit population sizes. To conclude, cormorants appear to compete little with fishery, with regards to free-living fish. The main problem is that cormorants sometimes damage and take away fish in fishing gears.</p>
48

Effects of Great Cormorant Predation on Fish Populations and Fishery

Engström, Henri January 2001 (has links)
The strong increase in number of Great cormorants Phalacrocorax carbo in Sweden in recent years has led to conflicts - particularly with fishery. This thesis focuses on the possible effects of cormorant predation on fish populations. In total, data from 15 lakes in South Sweden were included in this study while most studies were carried out in Lake Ymsen. The results suggest that the impact of cormorant predation on natural fish populations was small, and I observed no decline in fish mass after cormorants established. Cormorant predation on eel was difficult to evaluate because of several confounding factors. Ruffe, roach and perch were the most important prey species to the cormorants and most fish taken were small. Cormorants do not seem to catch species and sizes in proportion to their occurrence in the fish community. Total fish removal by cormorants varied considerably among lakes (0.2-15.0 kg/ha) and cormorant population sizes at the different lakes were significantly positively correlated with fishery catches, which in turn was significantly positively correlated with total phosphorous levels. Thus, cormorant densities in lakes, and perhaps elsewhere, seem to be governed chiefly by fish densities. The fact that cormorant predation appears not to reduce fish densities suggest cormorants to be regulated by other means than prey depletion. The mechanism behind population regulation could be a behavioural response of fish, making fish more difficult to catch for the cormorants. In recent years, cormorant populations have been subjected to intensive legal and illegal actions with the aim to reduce cormorant numbers. However, the actions currently carried are well below the efforts needed to limit population sizes. To conclude, cormorants appear to compete little with fishery, with regards to free-living fish. The main problem is that cormorants sometimes damage and take away fish in fishing gears.
49

Credibility and validation through syntheses of customary and contemporary knowledge : a thesis presented for the degree of Doctor of Philosophy in Maori Studies, Massey University, Wellington, New Zealand

Nixon, Marie Ann Zillah January 2007 (has links)
Content removed due to copyright restriction: Nixon, M. (2001). What are the potential benefits of eel consumption for Maori health? Te Taarere aa Tawhaki 1, 132-135. / This ground breaking doctoral thesis brings together science, history and the values derived from lore and tikanga to address a significant health issue for contemporary Maaori. The specific contribution of this research thesis is the combination of knowledge bases from two perspectives. The thesis first presents a scientific view, then a Maaori view, discovered through an interface of customary and contemporary knowledge. The method first examines Western academic theoretical methodologies, then, Kaupapa Maaori methodologies, then introduces and develops the concept of inherited knowledge supported by the mandatory Standards required in an academic context. Therefore the major findings present the syntheses of the two approaches. The framework used is reproducible through an accepted or approved example of something against which others are judged or measured. At this point the thesis explores the theoretical framework for a health intervention by surveying whether it is possible to combine knowledge traditions in a contemporary setting. Thus the accessed inherited traditional and scientific knowledge discovered in this thesis has been adapted for the nine point health intervention designed for Maaori participation. This thesis hypothesises that the staple long finned eel diet contained the essential fatty acid omega-3 and is presented as a metaphor for Hauora, thus being consistent with modern scientific knowledge where the scientific findings presented. The long finned eel was chemically assayed for the presence of the unsaturated essential fatty acid omega-3, and assayed again to assess the stability and quality of fresh and smoked eel. Type II diabetes mellitus is offered as a story and why it has suddenly occurred in Maaori subsequent to urban migration and thereafter. In addition a ten year study of Waikato hapuu supports the research that regular consumption of the long finned eel prevents Type II diabetes. And that prior to urban migration holistic practice, through established lifestyle choices and inherited knowledge, provided nutritional, other physiological benefits and broader wellness outcomes. The double vowel has been used for all te reo Maaori words in the thesis because that is the kawa or protocol of the Tainui Kiingitanga.
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Credibility and validation through syntheses of customary and contemporary knowledge : a thesis presented for the degree of Doctor of Philosophy in Maori Studies, Massey University, Wellington, New Zealand

Nixon, Marie Ann Zillah January 2007 (has links)
Content removed due to copyright restriction: Nixon, M. (2001). What are the potential benefits of eel consumption for Maori health? Te Taarere aa Tawhaki 1, 132-135. / This ground breaking doctoral thesis brings together science, history and the values derived from lore and tikanga to address a significant health issue for contemporary Maaori. The specific contribution of this research thesis is the combination of knowledge bases from two perspectives. The thesis first presents a scientific view, then a Maaori view, discovered through an interface of customary and contemporary knowledge. The method first examines Western academic theoretical methodologies, then, Kaupapa Maaori methodologies, then introduces and develops the concept of inherited knowledge supported by the mandatory Standards required in an academic context. Therefore the major findings present the syntheses of the two approaches. The framework used is reproducible through an accepted or approved example of something against which others are judged or measured. At this point the thesis explores the theoretical framework for a health intervention by surveying whether it is possible to combine knowledge traditions in a contemporary setting. Thus the accessed inherited traditional and scientific knowledge discovered in this thesis has been adapted for the nine point health intervention designed for Maaori participation. This thesis hypothesises that the staple long finned eel diet contained the essential fatty acid omega-3 and is presented as a metaphor for Hauora, thus being consistent with modern scientific knowledge where the scientific findings presented. The long finned eel was chemically assayed for the presence of the unsaturated essential fatty acid omega-3, and assayed again to assess the stability and quality of fresh and smoked eel. Type II diabetes mellitus is offered as a story and why it has suddenly occurred in Maaori subsequent to urban migration and thereafter. In addition a ten year study of Waikato hapuu supports the research that regular consumption of the long finned eel prevents Type II diabetes. And that prior to urban migration holistic practice, through established lifestyle choices and inherited knowledge, provided nutritional, other physiological benefits and broader wellness outcomes. The double vowel has been used for all te reo Maaori words in the thesis because that is the kawa or protocol of the Tainui Kiingitanga.

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