Thesis--Wisconsin. / Vita. Includes bibliographical references (leaves 97-107).

Thesis (Ph.D.)--Memorial University of Newfoundland, 2004. / Includes bibliographical references.

Thesis (Ph. D.)--University of Wisconsin--Madison, 1969. / Typescript. Vita. Description based on print version record. Includes bibliographical references (p. 209-212).

Partial migration, whereby populations consist of residents and migrants, is common among migrating organisms. Partial migration of aquatic organisms, however, remains largely under-studied even though many aquatic animals exhibit horizontal and vertical migrations during their lifetime. Macroinvertebrates of the genus Mysis exhibit diel vertical migrations (DVM). Some species have recently been observed to exhibit partial diel migrations where some individuals reside on the bottom throughout the night while others migrate into the water column. To test the hypothesis that individuals are fixed as residents or migrants, we compared demographic information and C and N isotope compositions of M. diluviana caught at night in pelagic and benthic regions of Lake Champlain. Our results suggest there are two distinct ecotypes of M. diluviana separated by migration behavior. The migrating ecotype was smaller than the resident ecotype and enriched in δ15N while the resident ecotype had a higher C:N ratio. Because we did not allow for gut evacuation prior to our analyses, we conducted a follow-up experiment to test the effect of gut content on isotope composition of M. diluviana. The experiments confirmed that differences between benthic- and pelagic-caught M. diluviana were not a result of gut contents at the time of capture. Fixed partial migration behavior in M. diluviana in Lake Champlain indicates that DVM of M. diluviana may be more complex than previously thought. Additionally, partially migrating Mysis spp. may represent a model study organism to test hypotheses about the causes and consequences of partial DVM behavior in aquatic invertebrates.

Thesis (Ph.D.) -- University of Montana, 2008. / Title from author supplied metadata. Description based on contents viewed on July 6, 2009. Includes bibliographical references.

Gegenstand der Arbeit war die Untersuchung der Rolle der Schwebegarnele Mysis relicta im pelagischen Nahrungsnetz des Breiten Luzins unter besonderer Berücksichtigung der trophischen Interaktionen zur Kleinen Maräne Coregonus albula. Schwerpunkte waren die Abundanz und räumlich-zeitliche Verteilung von M. relicta, C. albula und dem Zooplankton sowie die trophischen Beziehungen im Pelagial. Im Vergleich zu früheren Studien war M. relicta weiträumiger und mit höherer Dichte im Untersuchungsgebiet verbreitet. Dies war auf die Verbesserung der Wasserqualität zurückzuführen. Ähnliche Verteilungsmuster führten zu starken räumlichen Überlappungen von M. relicta und C. albula. M. relicta konsumierte vorwiegend abundantes Plankton. Es zeigte sich aber auch eine Präferenz für Cladocera. Aus den in vitro ermittelten Ingestionsraten wurde für die Situation im Freiland ein starker Fraßdruck von M. relicta auf das Zooplankton abgeleitet. In Kombination mit einer Überschneidung der Beutespektren führte das zur Nahrungskonkurrenz zwischen M. relicta und C. albula. Andererseits war M. relicta eine wichtige Beute für C. albula und wurde stark positiv selektiert. Die Fettsäuremuster der untersuchten Organismen waren überwiegend durch ihre Nahrung beeinflusst. Die Aufnahme von M. relicta wurde nicht durch das Auftreten spezifischer Fettsäuren bei C. albula nachgewiesen. Grundsätzlich entsprach der Energietransfer im Nahrungsnetz des Breiten Luzins allgemeinen Modellen mit 10 % Transfereffizienz zwischen benachbarten trophischen Ebenen. Im Einzelnen zeigten sich aber auch Abweichungen, die größtenteils auf M. relicta zurückzuführen waren. Durch ihre omnivore Ernährung und als Beute für C. albula schafft M. relicta zusätzliche Verbindungen zwischen den trophischen Ebenen. Insgesamt hat M. relicta einen weitreichenden Einfluss auf die Struktur und den Energietransfer des Nahrungsnetzes im Breiten Luzin, wodurch ihr Vorkommen für das Gewässer von besonderer Bedeutung ist. / The aim of the study was to investigate the role of the opossum shrimp Mysis relicta in the pelagic food web of Lake Breiter Luzin (Germany) with special focus on trophic interactions with European cisco Coregonus albula. Main aspects were the abundance and temporal and spatial distribution of M. relicta, C. albula and zooplankton as well as trophic relationships in the food web. As a result of improved water quality M. relicta showed a wider distribution and enhanced abundances in the study area than earlier investigations suggested. Due to similar diurnal vertical distributions a great spatial overlap was evident for M. relicta and C. albula. M. relicta fed mainly on highly abundant plankton. Besides, an overall preference for cladocerans was detected. By applying estimated in vitro feeding rates to field situations it could be shown that zooplankton was strongly exploited by M. relicta. This high demand combined with similar prey preferences of C. albula led to a strong food competition between M. relicta and C. albula. On the other hand M. relicta formed high amounts in the diet of C. albula and was always positively selected. Fatty acid composition of examined organisms resembled the composition found in their dietary resources. The intake of M. relicta could not be detected by a specific fatty acid composition in C. albula. Considering highest and lowest trophic levels, transfer efficiency in Lake Breiter Luzin fit into general models assuming a transfer of 10 % between neighbouring trophic levels. Transfer between intermediate trophic levels partly differed from this general pattern. This was connected to the existence of M. relicta. Being omnivorous and by providing an important food source for C. albula the mysid established additional links between trophic levels in the food web. In summary, M. relicta is a significant factor in structuring the food web of Lake Breiter Luzin and has profound impact on the entire lake ecosystem.