Thesis (Ph.D.)--University of Wollongong, 2004. / Typescript. Includes bibliographical references.

Typescript. / Bibliography: leaves 159-174. / Microfiche. / xvi, 174 leaves ill., maps

Scaup (Aythya spp.) are suspected of consuming substantial quantities of fish from Arkansas commercial baitfish and sportfish farms. We investigated the foraging ecology and depredation impact of scaup on farms by surveying ponds and collecting scaup during two autumn-winters (2016-2018) in Arkansas. Scaup abundance and fish they consumed were highly variable between winters. More scaup were present and they ate more fish during the second winter (2017-2018) than the previous winter. In the second year, there were an estimated 874,941 scaup use-days and 18% of Lesser Scaup diet was fish. We found that scaup use of ponds was more likely in colder winters and on larger Golden Shiner, Fathead Minnow, and Lepomis spp. ponds stocked at high densities. These results will inform stakeholders on the extent of losses of fish to these birds, and methods to efficiently allocate resources for timely harassment of scaup from fish ponds.

Assignment (MPhil)--Stellenbosch University, 2003. / ENGLISH ABSTRACT: Many species of tilapia such as Oreochromis mossambicus are euryhaline, able to adapt to different salinity waters. Their ability to withstand high salinity levels has given rise to the possibility of using tilapia as baitfish for tuna line fishery. The purpose of the study was to determine the survival rate of tilapia O. mossambicus during direct transfer from freshwater to the salinity levels of 0, 15, 20, 22.5, 25, 27.5, 30, 32.5, and 35 ppt. The data was analysed through means of univariate ANOVAand regression analysis. O. mossambicus showed no mortality to all salinity regimes up to 25 ppt. Mortality was observed at 27.5 ppt, with 100% mortality at 35 ppt. LC 50 and LC 90 were found to be 30.5 and 34.2 ppt, respectively. The results indicate that tilapia (0. mossambicus) will survive a direct transfer to salinities up to 25 ppt. acclimation will be required in the event of transfer to salinity levels above 25 ppt, in order to prevent significant levels of mortalities. / AFRIKAANSE OPSOMMING: Meeste van die tilapia spesies soos Oreochremis mossambicus het die vermoë om by water van verskillende soutgehaltes aantepas. Dit is hierdie vermoë om hoë sout vlakke te weerstaan wat die moontlikheid vir gebruik as lewende aas in die tuna langlyn visvangbedryf moontlik maak. Die doel van hierdie studie was om die oorlewingsvlak van tilapia, O. mossambicus te bepaal by die oorplasing van varswater direk na soutwater by vlakke van 0, 15, 20, 22.5, 25, 27.5, 30, 32.5, en 35 dele per duisend. Die data is verwerk deur gebruik te maak van eenvariant ANOVAen regressie analises. O. mossambicus het geen mortaliteite tot gevolg gehad by al die oorplasings van vlakke tot en met 25 dele per duisend sout nie. Mortaliteite is wel gevind vanaf 27.5 dele per duisend, met 100 % mortaliteite by 35 dele per duisend. LC 50 en LC90 was gewees 30.5 en 34.2 dele per duisend onderskeidelik. Die resultate toon aan dat tilapia (0. mossambicus) sal oorleef by direkte oorplasing na soutwater by vlakke van tot en met 25 dele per duisend. Tilapia wat na hoër vlakke as 25 dele per duisend oorgeplaas wil word, sal eers geleidelik moet akklimatiseer om mortaliteite te beperk.

Mémoire (M.P.Aquat.) -- Université du Québec à Chicoutimi, 1992. / Document électronique également accessible en format PDF. CaQCU