Thesis (Ph. D.)--Virginia Polytechnic Institute and State University, 1995. / Vita. Abstract. Includes bibliographical references (leaves 162-174). Also available via the Internet.

Thesis (M.E.S.)--The Evergreen State College, 2001. / Title from title screen viewed (3/20/2008). Includes bibliographical references (leaves 41-44).

Thesis (Ph. D.)--Oregon State University, 2006. / Printout. Includes bibliographical references (leaves 284-312). Also available on the World Wide Web.

The ecological communities we observe today are a product of the bidirectional interactions between ecological and evolutionary processes. Although the effects of ecological processes on population divergence and speciation have been studied extensively, far less is known about the effects of divergence and speciation on ecological dynamics. This is especially true for effects of ecological speciation processes on higher trophic levels. In this thesis I focus on how divergence in the European whitefish (Coregonus lavaretus) affects a guild of six piscivorous bird species. Previous studies have indicated that population densities of these species are higher on lakes with polymorphic whitefish than on lakes with monomorphic whitefish. Here I test the hypothesis that the high densities of piscivores is a response to the rich food resource provided by dwarf whitefish ecotypes, which are of suitable size and occur in very high abundance.To test this hypothesis I analyzed fecal samples from piscivorous birds in lakes with polymorphic whitefish, using samples from lakes with monomorphic whitefish as controls. With the method of ddPCR (digital droplet Polymerase Chain Reaction) the amount of DNA from different prey fish species in the droppings of six fish-eating birds was quantified and converted to proportional abundances. The results shows that the proportion of whitefish in the diet of the entire fish-eating guild was significantly higher in lakes with polymorphic whitefish (44%) than in lakes with monomorphic whitefish (18%). Species-level analyses showed that this result also holds for both black-throated loon (Gavia artica) and red-throated loon (Gavia stellata). Common merganser (Mergus merganser), red-throated merganser (Mergus serrator) and terns (Sterna paradisaea and Sterna hirundo) did not show any difference between the two lake categories. Thus, my study supports the idea that the evolution of small-sized whitefish ecotypes provides a profitable food source for piscivorous birds. However, the finding that only some species of piscivorous bird populations seem to rely heavily on dwarfed whitefish as food suggests that also some other aspect of the speciation process may favor these species. Thus, more studies are needed to further assess what effects polymorphic whitefish have on piscivorous bird populations.

Piscivorous avian species are of particular importance in Mississippi due to their depredation of cultured catfish throughout the states aquaculture industry. The three most common of these species include the double-crested cormorant (Phalacrocorax auritus), great blue heron (Ardea herodias), and great egret (Ardea alba). Information on these species aquaculture use can aid in effective and ethical management while also providing insight into their foraging ecology and habitat use, which is particularly important given these species augment their nutritional requirements using man-made food sources. The objectives of this research were to explore numerous aspects of avian foraging ecology in relation to aquaculture at multiple spatial and temporal scales using historic and contemporary aerial survey data. First, we examined the distribution and abundance of species on aquaculture at both the farm and pond scale. Pond contents and characteristics influenced each species, including culture practices and surroundings. In all cases, the amount of aquaculture was positively related to species abundances. Pond and farm selection relationships were species-specific, illustrating inherent differences in their foraging ecology. Consequently, specific management actions will depend on the targeted species. We also found cormorant densities on aquaculture has not changed in the past 15 years, even though aquaculture has significantly declined. Second, we measured cormorant distribution between aquaculture and natural water bodies. The highest use of aquaculture occurred when producers were not allowed to use lethal control, whereas the lowest use occurred when producers could. This trend highlights the potential influence of mortality risk on cormorants' foraging distribution. Lastly, we examined cormorant dynamics at the regional scale using roosting data. We found the Midwest breeding population of cormorants has been increasing, but the abundance of cormorants wintering in Mississippi has been decreasing, suggesting aquaculture is the primary cause of inhabitation of the state. We also found the phenology of cormorant spring migration is occurring earlier each year. Aquaculture area had a positive influence on cormorant distribution at roosts particularly prior to migration. These findings suggest changes in agriculture, and potentially climate change, can influence phenology, distribution, and abundance of avian species at multiple scales.

Thesis (Ph.D. (Zoology)) -- University of the North, 1996 / Refer to document

Made available in DSpace on 2015-04-20T12:33:49Z (GMT). No. of bitstreams: 1 Tese Kedma yamamoto final agosto 2011.pdf: 1602993 bytes, checksum: 84439325cb6d0fa680dee7acd14a9088 (MD5) Previous issue date: 2011-06-14 / FAPEAM - Fundação de Amparo à Pesquisa do Estado do Amazonas / Studies on the role of artificial reefs and related structures are quite widespread in the marine literature, however knowledge about its effects on the biota of inland waters is still incipient. A study was conducted in lakes National Park Anavilhanas, Manaus / Am, to analyze the effects of increasing heterogeneity through the use of artificial attractors on the fish assemblages and populations of piscivorous in open water habitat. We also tested the influence of the attractors in two fixed levels of environmental complexity and its relationship to biotic and abiotic factors. Samples were taken four lakes using batteries of different sizes of gillnets, in the morning and evening for twenty-four months. The results showed that the artificial attractors exert a strong influence on fish assemblages in dry seasons, the abundance and diversity respond related to this environmental change. The heterogeneity near the attractors not in the abundance and diversity of the assemblages. Analysis of variance with repeated measures indicated significant differences between attractor and control for the number of species and the Berger-Parker dominance, using as response variable numerical abundance and weight. The environmental variables indicated by significant regression on the diversity of piscivores pH, oxygen and temperature. The number of species of piscivores was higher than in control attractors. Cichlid populations occurred only in areas of the attractor and the period of drought. / Estudos sobre o papel de recifes artificiais e estruturas correlatas são bastante difundidas na literatura marinha, entretanto o conhecimento sobre seus efeitos na biota de águas interiores ainda é incipiente. A pesquisa foi desenvolvido em lagos do Parque Nacional de Anavilhanas, Manaus/Am, para analisar os efeitos do aumento da heterogeneidade ambiental através do uso de atratores artificiais, sobre a estrutura das assembléias de peixes e de populações de piscívoros em habitat de água aberta. Testamos também, a influência dos atratores fixados em dois níveis de complexidade ambiental e suas relações com fatores bióticos e abióticos. Foram realizadas coletas durante dois ciclos hidrológicos, em quatro lagos usando baterias de malhadeiras de diferentes tamanhos, com despescas pela manhã e à noite durante vinte e quatro meses. Os resultados revelaram que os atratores artificiais exercem forte influência sobre as assembléias de peixes nas estações secas, a abundância e a diversidade respondem de forma relacionada a esta mudança ambiental. A heterogeneidade ambiental próxima aos atratores não apresentou influência na diversidade e abundância das assembléias. A Análise de variância com medidas repetidas no tempo indicou haver diferenças significativas entre atrator e controle para o número de espécies e na dominância de Berger-Parker, usando como variável resposta a abundância numérica e peso. As variáveis ambientais significativas indicadas pela Regressão sobre a diversidade de piscívoros foram o pH, oxigênio e a temperatura. O número de espécies de piscívoros foi maior nos atratores do que no controle. Populações de ciclídeos ocorreram somente nas áreas de atrator e durante o período de seca.

Submitted by Lara Oliveira (lara@ufersa.edu.br) on 2017-02-17T20:18:04Z No. of bitstreams: 1 CarlosWFM_DISSERT.pdf: 2074387 bytes, checksum: d15d040743afcab33bb24b0c294d916d (MD5) / Approved for entry into archive by Vanessa Christiane (referencia@ufersa.edu.br) on 2017-03-21T14:44:13Z (GMT) No. of bitstreams: 1 CarlosWFM_DISSERT.pdf: 2074387 bytes, checksum: d15d040743afcab33bb24b0c294d916d (MD5) / Approved for entry into archive by Vanessa Christiane (referencia@ufersa.edu.br) on 2017-03-21T14:49:32Z (GMT) No. of bitstreams: 1 CarlosWFM_DISSERT.pdf: 2074387 bytes, checksum: d15d040743afcab33bb24b0c294d916d (MD5) / Made available in DSpace on 2017-03-21T15:05:59Z (GMT). No. of bitstreams: 1 CarlosWFM_DISSERT.pdf: 2074387 bytes, checksum: d15d040743afcab33bb24b0c294d916d (MD5) Previous issue date: 2016-03-31 / Alien species are causing various environmental impact on aquatic ecosystems throughout the world. As an example, alien fish introductions piscivorous habit have been associated with dramatic reductions in local diversity of native fish assemblages. To predict these impacts is necessary to understand environmental factors related to predation and selectivity of alien piscivorous fish, and some factors that may limit the invasive potential and the establishment of these non-native species due to reduction in the capture of prey, such as turbidity and complexity habitat as the presence of weeds for shelter. Thus, this study seeks to understand the Cichla kelberi species that has evaluated experimentally in a completely randomized design. The experiment was conducted in aquaculture center UFERSA, in plastic tanks containing approximately 500L of water, each with the presence of only predator, which was subjected to environments where the turbidity had 3 different levels (0, 60 and 120 NTU); 2 of macrophytes (presence or absence) and the selectivity of prey was evaluated by Chesson index, is offering 2- different prey sizes (the smallest with 2.87 ± 0.25 cm and the largest with 3.91 ± 0, 11 cm). The results of this study revealed that high levels of turbidity (120 NTU) consumption of prey has been reduced significantly; the presence of aquatic weeds did not affect the predator consumption and there was a preference for smaller prey of Oreochromis niloticus. In conclusion, this study showed behavioral information about the alien C. kelberi and factors that may limit their predation and providing empirical support for greater understanding of the species. Combined, these results support the hypothesis of the study and suggest that the impact of risk is reduced predation on aquatic ecosystems high turbidity and the presence of larger prey / Espécies alienígenas são causadoras de diversos impactos ecológicos em ecossistemas aquáticos em todo o mundo. A exemplo disso, introduções de peixes alienígenas de hábito piscívoro têm sido associadas a drásticas reduções na diversidade local de assembleias de peixes nativos. Para prever esses impactos é necessário compreender fatores ambientais relacionados à predação e seletividade de peixes piscívoros alienígenas, sendo que alguns fatores que podem limitar o potencial invasivo e o estabelecimento dessas espécies não nativas devido a redução da captura de presas, tais como turbidez e complexidade de hábitat como a presença de macrófitas como abrigo. Diante disso, este estudo busca compreender a espécie Cichla kelberi, que foi avaliada experimentalmente em um delineamento inteiramente casualisado. . O experimento foi realizado no centro de aquicultura da UFERSA, em tanques plásticos, contendo aproximadamente 500L de água, cada um com a presença de único predador, que foi submetido a ambientes onde a turbidez apresentava 3 níveis distintos (0, 60 e 120 NTU); 2 de macrófitas (presença e ausência) e a seletividade de presas foi avaliado pelo índice de Chesson, ofertando-se 2 tamanhos de presas diferentes (a menor com 2,87 ± 0,25 cm e a maior com 3,91 ± 0,11 cm). Os resultados desse estudo revelaram que em níveis elevados de turbidez (120 NTU) o consumo de presas foi reduzido significativamente; a presença de macrófitas aquáticas não interferiu no consumo do predador e observou-se preferência por presas de menor tamanho de Oreochromis niloticus. Concluindo, o presente estudo apresentou informações comportamentais sobre o alienígena C. kelberi e fatores que podem limitar sua predação e fornecendo suporte empírico para maior compreensão da espécie. Combinados, estes resultados suportam a hipótese do estudo e sugerem que o impacto do risco predação será reduzida em ecossistemas aquáticos de alta turbidez e na presença de presas maiores / 2017-02-17

The commercial production of channel catfish (Ictalurus punctatus) is major industry in Mississippi. Infections of channel catfish with the digenetic trematode Bolbophorus damnificus have often been associated with heavy economic losses in the industry. To efficiently control transmission of this trematode, the avian hosts need to be identified. In the first study, two American white pelicans, two double-crested cormorants, two great blue herons, and two great egrets were fed channel catfish infected with B. damnificus metacercariae. The presence of Bolbophorus damnificus ova in pelican feces at three days post infection (dpi) indicated the pelicans had patent infections. Mature B. damnificus were recovered from the intestines of both pelicans at 21 dpi. No B. damnificus infections were observed in the other bird species. In a second study, 33 American white pelicans, 34 double-crested cormorants, 35 great blue herons, and 32 great egrets were collected in the Mississippi Delta. The prevalence of B. damnificus in the American white pelican was 93.9%, with an average of 158 B. damnificus found per bird (range 0-681). Bolbophorus damnificus was not found in any of the other bird species. The results of these two studies confirm that the AWPE is the only proven natural host for B. damnificus. In a third study, two previously undescribed cercariae were found infecting rams-horn snails in commercial catfish ponds. In challenge studies, channel catfish were exposed to both cercariae types. Only one type of cercariae (type I) was infective to channel catfish. The first evidence of type I metacercariae was seen histologically at 14 dpi and grossly at 21 dpi. Development continued until 120 dpi, when both gross examination and histology suggested that the metacercariae were mature. The type I metacercariae appeared to cause little host damage. Molecular analysis of the 18S rRNA gene region indicated that the type I cercariae and metacercariae may be a species of Clinostomum. The data generated in these three studies provides additional information that can be used in the development of efficacious management schemes to control digenetic trematodes infecting commercial catfish.

To understand the behavior of a species under the reproduction aspects, growth, birth rate, mortality and migration is indispensable the knowledge of his alimentary behavior, still more if treating of fishes with habit alimentary piscivorous that they occupy the top of the trophic chain exercising a fundamental paper in the communities' structuring. This study had for objectives to analyze the feeding of the fish-dog, Acestrorhynchus pantaneiro in three rivers of Rio Grande do Sul, verifying which prey of larger preference and analyzing the relationship of the size of the prey x predator, and for Rio Vacacaí and Rio dos Sinos the group is considered allochthonous for the system. It was analyzed 380 examplaries captured bimonthly among the years of 2010 and 2011 for Rio Jaguari, which presented the index of vacuity of 0,74. In the rivers Vacacaí end of the Sinos 225 examplaries were analyzed, being 107 to Rio Vacacaí, captured in five points in the four seasons, presenting an index of vacuity of 0,62 and 118 examplaries captured to Rio dos Sinos in the summer and autumn of 2011, presenting result of IV of 0,41. In Rio Jaguari, differences were not verified between atmosphere lentic and lotic, regarding the capture, the bimonth with higher temperatures presented larger number of captured examplaries, and the studied species presented larger alimentary activity at dusk and at night to Rio Jaguari and at night for in the rivers Vacacaí end oh the Sinos. Through the analysis of the size of the prey x predator it could be verified for the three rivers studied that prey larger they are ingested by predators also larger. The diet of the species came fish-eating essentially feeding preferentially of small characins feeds. Studies of the alimentary behavior of species fish-eating are necessary, overcoat of species allochthonous, seeking to understand the relationships of those species as predators of chain top in aquatic atmospheres, controlling the feeds populations. / Para compreender o comportamento de uma espécie sob os aspectos de reprodução, crescimento, natalidade, mortalidade e migração, é indispensável o conhecimento de seu comportamento alimentar, ainda mais se tratando de peixes com hábito alimentar piscívoro que ocupam o topo da cadeia trófica exercendo um papel fundamental na estruturação de comunidades. Este estudo teve por objetivos analisar a alimentação do peixe-cachorro, Acestrorhynchus pantaneiro em três rios do Rio Grande do Sul, verificando quais presas de maior preferência e analisando a relação do tamanho da presa x predador, sendo que para o Rio Vacacaí e Rio do Sinos a espécie é considerada alóctone para o sistema. Analisou-se 380 exemplares capturados bimestralmente entre os anos de 2010 e 2011 pra o Rio Jaguari, o qual apresentou o índice de vacuidade de 0,74. Nos rios Vacacaí e dos Sinos foram analisados 225 exemplares, sendo 107 para o Rio Vacacaí, capturados em cinco pontos nas quatro estações do ano, apresentando um índice de vacuidade de 0,62 e 118 exemplares capturados para o Rio dos Sinos no verão e outono de 2011, apresentando resultado de IV de 0,41. No Rio Jaguari, não foram constatadas diferenças entre ambiente lêntico e lótico, com relação à captura, os bimestres com temperaturas mais elevadas apresentaram maior número de exemplares capturados, sendo que a espécie estudada apresentou maior atividade alimentar ao entardecer e à noite para o Rio Jaguari e à noite para os rios Vacacaí e Sinos. Através da análise do tamanho da presa x predador pôde-se constatar para os três rios estudados que presas maiores são ingeridas por predadores também maiores. A dieta da espécie apresentou-se essencialmente piscívora alimentando-se preferencialmente de pequenos caracídeos forrageiros. Estudos do comportamento alimentar de espécies piscívoras são necessários, sobretudo de espécies alóctones, visando entender as relações dessas espécies como predadores de topo de cadeia em ambientes aquáticos, controlando as populações forrageiras.