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Scenedesmus obliquus was grown in batch cultures at varying concentrations of digested dairy medium ranging from 200 to 2,000 ug-at N ⁻¹. Higher growth rates were observed at low N-concentrations while higher cell yields were observed at high N-concentrations. Aeration enhanced both algal growth rates and biomass yields. Results show an advantage in adjusting the nitrogen to phosphorus atomic ratio of the medium. More biomass was produced in cultures with higher N:P ratios. The algal biomass produced was used as food for the freshwater cladoceran, Daphnia pulex F. Three feeding levels were used: 50,000, 100,000 and 150,000 cells-ml⁻¹ . However, no significant differences were observed in both Daphnia biomass yields and biomass conversion efficiencies. The tendency of Scenedesmus cells to settle down in the bottom and cling to the sides of the tank presented a major problem in the study. Intensive feeding did not increase the biomass production of Daphnia, although larger-sized adults with larger brood sizes were produced. Animals in culture reached a density of 1.24 animals-ml⁻¹Aand obtained conversion efficiencies as high as 40-50%. / Land and Food Systems, Faculty of / Graduate

Following the abatement of domestic sewage pollution xii in the lower Logan River , the fish population was investigated in terms of abundance, growth, fecundity, production, mortality, age class structure, species diversity, distribution and movements during 1970 and 1971. Three general groupings of fish were identified in the study area on the basis of species composition, abundance and distribution using a cluster analysis technique. These were located in 1) the tributary stream (7-Mile Creek) which previously transported sewage to the river and 2) above and 3) below 7-Mile Creek in the main stream of the Logan River. A "transition" population was present in the river near the confluence of 7-Mile Creek. Species diversity was predictable on the basis of four physical variables including percent riffle, a measure of bank cover, stream sinuosity and gradient. Percent riffle appeared to be the most important variable in predicting the "Trophic Condition Index" of the fish population. An information theory function was used to determine the extent of fish movement within the study area. Of the four dominant species in the river (carp, mountain whitefish, Utah suckers and brown trout) only the brown trout demonstrated an apparent response to the pollution abatement by reducing the extent of its movements at this time. Seasonal growth patterns were strikingly similar among the species examined with maximum growth occurring during the spring months. Extensive weight losses, attributed to high population densities and a decline in the invertebrate forage base, occurred during the summer of both 1970 and 1971, particularly in the older age classes of mountain whitefish and brown trout. Production of carp, mountain whitefish and brown trout and Utah suckers was assumed to approximate total fish production in the river. Whitefish production above and below 7-Mile Creek was estimated to be 3. 87 and 1.65 gm/m 2/yr respe ctive ly for the period June 1970 to May 1971. Carp production in these two areas was estimated to be 22.86 and 10.45 gm/m 2/yr for the same period. Brown trout production was estimated to be 5.94 gm/m 2/yr above 7-Mile Creek while production of Utah suckers in the study area was estimated to be 2-3 gm/m 2/yr. Weighted production for the entire study area was estimated to be 23.5 gm/m 2/yr. Evidence is presented which suggests that fish production has increased following the pollution abatement.

The green sunfish Lepomis cyanellus Rafinesque is a member of the sunfish family Centrarchidae. Curtis states that all members of the sunfish family are native only to North America, and are primarily warm-water fish. According to Jordan and Evermann the green sunfish is generally abundant in all suitable waters from central Ohio and Indiana to the Rio Grande. Forbes and Richardson five the general distribution of the green sunfish to be from the Great Lakes to Mexico, the Mississippi Valley, and everywhere in small sluggish streams except east of the Alleghanies and in Canada. The green sunfish is not native to Utah, but has been introduced in a number of ponds in the state. It is not considered important as a pan-fish because of its limited range and small size.

Introduced brook trout (Salvelinus fontinalis) are implicated as a primary factor leading to the decline in distribution and abundance of native cutthroat trout (Oncorhynchus clarkii). However, not all introductions are successful, suggesting local conditions influence the success of invasions. Therefore, I sought to determine the multi-scale factor(s) that influence brook trouts’ invasion success of native Bonneville cutthroat trout (Oncorhynchus clarkii utah) habitats in Mill Creek, Utah. I conducted patch occupancy surveys to determine watershed-scale brook trout and cutthroat trout distribution. I also determined the relative abundance of brook trout and cutthroat trout at the reach-scale by conducting three-pass depletion electrofishing surveys at ten index sites throughout the drainage. Upon completion of those surveys, I collected key watershed and reach-scale biotic and abiotic data twice during base-flow conditions. In addition, to determine watershed-scale population connectivity and the potential for upstream invasion by brook trout, I assessed fish movement using two-way weir traps. At the watershed-scale, stream slope appeared to limit brook trout invasion into some portions of the drainage. Intermittent stream-flows and extreme levels of stream slope (> 10%) appeared to limit cutthroat trout distribution. At the reach-scale, regression analyses indicated aquatic invertebrate abundance and low winter water temperatures may have influenced the abundance of brook trout, but my models explained little variation in cutthroat trout abundance overall. I observed high rates (74%) of site fidelity amongst brook trout, and mobile brook trout moved short distances (range=62-589 meters) overall. Cutthroat trout also exhibited high site fidelity (92%), but their movement was more variable, as few individuals moved long distances (up to 12.15 km). These findings will help prioritize cutthroat trout management actions in this watershed, and will be useful in determining why brook trout are successful invaders in some systems, yet remain in low and patchy abundance in others.

Nine hemoglobins from adult rainbow trout have been isolated by starch gel electrophoresis using a Trisborate buffer system, pH 8.7. Six fast and two slow anodally migrating hemoglobins, and one slow cathodally migrating hemoglobin were observed in all specimens. The nine hemoglobins have been purified by DEAE cellulose ion exchange chromatography followed by starch gel electrophoresis. The subunit structure of each purified hemoglobin has been partially examined by gel electrofocusing (GEF) in .5 percent polyacrylamide gels containing 8M urea and lmM dithiothereitol (DTT). Tetrameric combinations of one, two, three, and four polypeptide chains are present. Twelve hemoglobins have been isolated from cutthroat trout. Six fast and two slow anodally migrating hemoglobins, and four cathodally migrating hemoglobins were observed in most of the specimens. Hemoglobin polymorphism has been detected in a population of Yellowstone Lake cutthroat trout, Yellowstone Park, Wyoming. Six phenotypic patterns were evident.