"The text of this report was submitted as a doctoral dissertation to the ... University of Michigan." / Includes bibliographical references (p. 155-175).

Thesis--Wisconsin. / Vita. Includes bibliographical references (leaves 256-269).

Thesis (Ph. D.)--University of Wisconsin, Madison, 1988. / eContent provider-neutral record in process. Description based on print version record. Includes bibliographical references (leaves 198-207).

Thesis (Ph. D.)--University of Wisconsin--Madison, 1970. / Typescript. Vita. Includes bibliographical references (leaves [183]-193).

No description available.

Orientador: Francisco Manoel de Souza Braga / Banca: Norma Segatti Hahn / Banca: Francisco Langeani Neto / Resumo: Estudos sobre alimentação natural de peixes contribuem para o conhecimento básico da biologia das espécies, compreensão da organização trófica do ecossistema e conhecimento das interações entre as espécies. O presente estudo visou estudar a biologia alimentar da ictiofauna na área de influência do reservatório da usina Mogi Guaçu e nas lagoas marginais naturais da Estação Ecológica (fazenda Campininha), município de Mogi Guaçu-SP, com o intuito de responder as seguintes questões: (1) quais recursos alimentares as espécies estão utilizando? (2) existe alguma preferência alimentar para as espécies? (3) ocorrem alterações sazonais na dieta das espécies? Para a captura dos peixes, foram utilizadas redes de espera, puçá e armadilhas do tipo covo. Foram capturados 2341 exemplares de 41 espécies pertencentes a cinco ordens e 15 famílias. A ictiofauna nos ambientes estudados foi composta por peixes típicos da bacia do alto Paraná indicando uma condição que, embora alterada, apresenta espécies essencialmente nativas desta região. Foram analisados 370 estômagos provenientes de 1900 exemplares de peixes pertencentes a 14 espécies nos dois ambientes. Entre os itens consumidos pelos peixes, detritos e insetos (fragmentos) foram os que mais contribuíram para a alimentação das espécies no reservatório e nas lagoas marginais, respectivamente. Verificou-se que a dieta das espécies no reservatório e nas lagoas marginais foi significativamente correlacionada entre os períodos seco e chuvoso não ocorrendo, portanto, alterações sazonais. Os itens de origem autóctone tiveram uma participação maior na dieta das espécies, incluindo algas, insetos aquáticos e detritos entre os mais freqüentes. Foram determinadas cinco guildas tróficas para as 17 espécies analisadas. No reservatório os curimatídeos compuseram a guilda... (Resumo completo, clicar acesso eletrônico abaixo) / Abstract: Studies involving fishes natural feeding habits increases the knowledge about species biology, understanding the trophic structure and species interaction. This work was conducted to study the feeding biology of fishes from Mogi Guaçu reservoir and some oxbow lakes from a protected area known by fazenda Campininha (Mogi Guaçu municipality), to answer the following questions: (1) which food resources fishes are using? (2) is there any food resource preferred for them? (3) seasonal alterations occur in fishes diets? Fishes were sampled using simple gillnets with different meshes sizes and traps. We captured 2341 fishes from 41 species belonging five orders and 15 families. The fish fauna composition revealed typical species from high Paraná river system indicating the presence of native species although the human alterations in the region. We analyzed 370 stomachs from 1900 individuals (14 species from both areas). They consumed mostly detritus and insects (fragments). Fishes diet on reservoir and oxbow lakes were significantly correlated between the seasons and no changes were observed. The majority items consumed were from autochthonous origin, including algae, aquatic insects and detritus that appeared frequently. Five trophic guilds were determined to the 17 species sampled. Curimatidae were the most abundant species corresponding to detritivorous fishes, followed by omnivorous, invertivorous, piscivorous and herbivorous fishes. Four trophic guilds were found in oxbow lakes where the invertivorous fishes were the most abundant (Hoplosternum littorale, Hyphessobrycon bifasciatus and Hyphessobrycon eques), followed by detritivorous, omnivorous and piscivorous fishes. The frequencies obtained from stomach repletion, fat accumulation and gonadal maturation degrees were related with fish's conditions. / Mestre

Abstract In this thesis, I used the Chironomid Pupal Exuvial Technique (CPET) to detect anthropogenic impacts and to determine chironomid species composition in boreal rivers and lakes. The main objectives of the thesis research were i) to evaluate the importance of timing of sampling in the use of the CPET method (I, II), ii) to identify chironomid indicators of different environmental conditions (II, III, IV), and iii) to compare performance of the CPET method and more traditional sampling techniques in detecting anthropogenic impacts and chironomid species composition (III, V). I also determined emergence patterns of lotic chironomids in southern Finland (II, IV). Timing of sampling was found to be a critical design factor in the application of the CPET, especially if the trophic gradient between study sites was short. Sampling occasions need to match with the emergence periods of indicator chironomid taxa to ensure the maximum likelyhood of detecting human impacts, if any exist. However, the optimal timing of sampling varies spatially and is dependend on several environmental factors, such as latitude, altitude and trophic gradient. The shift in taxonomic composition of emerging chironomids was found to be especially rapid in spring, and tended to decrease towards autumn. This was probably due to the short emergence periods of some spring-emerging univoltine species, with their annual emergence taking only a few weeks. In contrast to whole genera, the detection of a certain species may require accurate timing of sampling. Thus, among-site differences observed at species level may reflect spatially varying emergence patterns rather than true differences in community composition. On the other hand, because of the among-species variation in species' tolerances towards, for example eutrophication, genus level identification may mask subtle differences between study sites. Nevertheless, for most monitoring purposes genus level identification seems practical and adequate, although species level resolution is desirable. Comparisons of the CPET method and more traditional grab sampling showed that pupal exuvial samples provided a more complete picture of the chironomid fauna, and that this information was obtained cost-effectively. Further, the integrative nature of the CPET was found to be critically important in the assessment of both lotic and lentic habitats. Sampling only a single macrohabitat type may result in biased estimates of the ecological condition of the whole water body. Further, in comparison to profundal grab samples, integrating species from various habitats using the CPET method appeared to have only a minor negative influence on the signal strength. Determination of emergence patterns of lotic chironomids showed that nearly 200 chironomid species occurred frequently in rivers of southern Finland. A major proportion of species richness was accounted for the sub-families Chironominae (emerging mainly during the summer months) and Orthocladiinae (spring and autumn). Overall, these studies demonstrated that the CPET is a cost-effective and sensitive method for the assessment and monitoring of freshwaters, and should be considered as an alternative and/or supplementary tool to more traditional sampling methods.

Hydrological and meteorological observations related to ice conditions on rivers in the Nelson drainage system are compared statistically to determine the measure of agreement between them. The results show a high degree of positive correlation. The areal variability of ice formation, ice disintegration, mean length of the ice-free season, and the standard deviation of first-ice and last-ice are plotted on maps. The data has been based upon ten-year mean dates and also the entire 1921 to 1950 period. The progress of ice formation and disintegration is examined statistically both latitudinally and also along the major tributaries of the Nelson River. Results indicate that first appearance of ice affecting discharge generally follows the expected north to south pattern; no systematic progression along tributaries in either an upstream or a downstream direction is apparent. On each major tributary tested, ice disintegration progresses downstream. Latitudinal progress follows a south to north pattern with the exception of the southeasterly-flowing portion of the Assiniboine River. Trends and fluctuations in ice formation and disintegration are studied by five-point filtered series. Break-up (last-ice) occurred earliest in the mid-1940’s whereas freeze-up showed no definite trend. Filtered series of ice formation dates appear to exhibit greater co-variability than those of ice disintegration dates. The variability of break-up on headwater streams could be a factor in limiting the covariability between last-ice records due to the dependency of break-up at downstream sites on upstream conditions. Trends in the length of ice-free (open) season for 1921 to 1950 are examined using cumulative percentual deviations from the mean. At most locations in the Nelson basin, the length of the ice-free season was shorter than average from 1921 to the early l930’s and longer than average in the last half of the record. Cumulative percentual deviations from the mean ice-free season are compared to those from the mean annual air temperature. Mean annual air temperatures and lengths of ice-free season do not appear to be significantly correlated in the Nelson basin. The study of factors affecting the formation and disintegration of river ice in the Nelson basin is limited primarily to a discussion of the relationships among air temperatures, ice conditions, and river discharge. The extent and variability of freezing and melting degree days before ice formation and disintegration are examined for the period 1921 to 1950. Local air temperatures are extremely variable before first-ice and last-ice dates. Ice may be reported when temperatures are above the freezing point; break-up may occur when temperatures are below the freezing point. Two possible explanations for first-ice being observed under thawing conditions are: (a) ice formed under freezing conditions upstream moving downstream: and (b) the pooling of cold air in entrenched valleys resulting in ice formation. The occurrence of last-ice under freezing conditions may be caused by freeze-thaw cycles weakening the structure of the ice cover combined with increases in discharge raising and cracking it. Mean discharge rates (1921 to 1950) prior to ice disintegration are computed and graphed for seven locations in the Nelson basin. Mean rates increase three to five times in the ten-day period preceding break-up. Increases in discharge appear to be one of the prime factors contributing to ice disintegration. / Arts, Faculty of / Geography, Department of / Graduate

Aquatic arthropods communities were examined with respect to factors determining species distributions and community structure in a series of eight lakes on the Chilcotin Plateau of British Columbia. Climate, altitude, physical location, water temperature and basin shape were similar for all lakes, and although size differed, no evidence was found for the influence of basin morphology on community structure. Salinity and vegetation characteristics differed widely among lakes, so three major processes were investigated: the association of (1) salinity with faunal communities, (2) salinity with floral communities, and (3) faunal with floral communities. These relationships were examined in light of diversity-stability hypotheses. The severity component of environmental stability was represented by salinity, and mean surface water conductivity ranged from 56 to 13115 μS cm-¹ at 25 °C. Salinity variations among lakes were determined primarily by the ions Na, HCO₃, CO₃, C1 and K. Two classification schemes (taxonomic and ecological) and several analytical techniques (community parameters and cluster analysis) indicated that the distribution and structure of faunal and floral communities were related to salinity. In total, 84 arthropod taxa and 26 macrophyte species were found and divided into three groups: those characteristic of high salinities (>5000 μS), of moderate or low salinities (<5000 μS), or tolerant of all salinities. Faunal assemblages in all lakes were dominated by filter feeders, and predators were more abundant in saline lakes. Shredders, collectors and predators were found in all the lakes, but saline lakes had fewer size groups. Floating leaved macrophytes occurred only in freshwater lakes, submerged forms were rare in highly saline lakes, and emergent forms were found in all lakes, although they were less abundant at high salinities. Generally, this study supports the hypothesis that saline habitats have less diverse communities than freshwater ones. In all floral and faunal sample sets, increased salinity was accompanied by a decrease in species richness. Virtually all measures of macrophyte community diversity and productivity were inversely correlated with salinity. Faunal subgroups must be examined separately when measures of community structure incorporate relative abundances. Patterns of association observed in the entire faunal community were dictated by the numerically dominant entomostracan subcommunity, and patterns in other subgroups were masked. Zooplankton trophic level diversity increased with decreasing salinity and changes in community composition were analogous to those of eutrophication. In both coleopteran and hemipteran communities, diversity decreased and density increased with increasing salinity. Possible causal mechanisms structuring each community are hypothesized. Faunal distributions corresponded to their known habitat preferences in terms of macrophyte communities. It was difficult to distinguish between the influence of salinity or macrophyte communities on animal communities as animal communities were often associated with both. / Science, Faculty of / Zoology, Department of / Graduate

In this study, incubations of sediments from three Swedish lakes, Parsen, Södra Teden, and Venasjön, were made to examine CH4 production during different temperatures. The incubations took place in two different climate rooms, one with a decreasing temperature and one with an increasing temperature with analyses made on the temperature levels around 10 and 20°C. Samples were taken and analyzed in a gas chromatograph. Results from the incubations ranged from -3,72 μmol m-2 d-1 up to 10,54 μmol m-2 d-1. A Mann Whitney test were made to test the statistical hypothesis if there were any differences in CH4 production between the temperatures. Only Venasjön were significantly different in CH4 production (P=0.01) while Södra Teden and Parsen were non-significant. Discussed points were that the lakes have potential for CH4 production, but there is several factors beside the temperature change that both favors and inhibit the production rates. Södra Teden displayed an individual measurement with a high production rate which suggest a major potential for CH4 production. The study concludes that the temperature effect is not clear in this study due to the lack of significant difference between the temperature levels. It also concludes that we need a bigger understanding of the lakes to be able to draw further conclusions of the results. A final conclusion was that it did not matter whether the sediments were exposed for a temperature increase or a decrease. The study suggested that further research is needed for similar lakes with more samples to enrich the statistical analyses and develop the knowledge about which factors that regulates CH4 production in Swedish freshwater lakes. / I denna studie genomfördes inkubationer av sediment från tre svenska sjöar, Parsen, Södra Teden, och Venasjön i syfte att undersöka CH4 produktion under olika temperaturnivåer. Inkubationerna genomfördes i två olika klimatrum, ett där temperaturen sänktes och ett där temperaturen höjdes. Temperaturperioderna som analyserades var omkring 20°C som den högre nivån och 10°C som den låga nivån. Provtagningar genomfördes och analyserades i en gaskromatograf för att kunna beräkna produktionen av CH4 under de olikatidsperioderna. Analysen gjordes utan att ta hänsyn till vilka prover som hade en sänkt temperatur eller en höjd temperatur. Resultaten från inkubationerna sträckte sig från -3,72 μmol/m-2 d-1 upp till 10,54 μmol/m-2 d-1.Från Södra Teden uppmättes ett enskilt värde som visar på att den sjön har en mycket stor potential för att producera metan. Andra diskuterade punkter är hur kvalitén och mängden organiskt material som och även hur mycket näringsämnen som finns tillgängligt i sjöarnas sediment. En av slutsatserna är att effekten av temperaturförändringen inte är tydlig på grund av bristen på signifikant skillnad mellan de båda temperaturnivåerna. Studien visar också på att vi behöver en större förståelse av sjöarna i sig för att kunna dra ytterligare slutsatser av resultaten. Sist men inte minst så hade det minimal eller ingen betydelse om sedimenten utsattes för en temperaturhöjning eller en temperatursänkning. Studien förslår att ytterligare studier behöver genomföras på liknande sjöar med fler prover för varje sjö för att berika den statistiska analysen och utveckla kunskapen om vilka faktorer som reglerar bildningen av CH4 i svenska sjöar.