Feeding habits of fur seals (Callhorinus ursinus), sea lions (Eumetopias jubata) and harbour seals (Phoca vitulina) have been examined along the British Columbia coast. Collections were made out to 35 miles from shore. All pertinent published and unpublished data have been combined with the object of assessing the effect of pinniped predation upon commercially valuable fish stocks. A total of 126 harbour seal stomachs, 2,113 fur seal stomachs and 393 sea lion stomachs were available. Comparative anatomy of the digestive tract was examined and notable differences were found in the relatively longer digestive tract and late eruption of permanent teeth in the sea lion. Published data indicate that fur seals, sea lions, and harbour seals eat an amount of food equal to 6%of their body weight per day with a range of 2% to 11%. All samples were grouped as to season and area of collection and comparative seasonal feeding habits were discussed. The effect of the reproductive period upon feeding habits was examined: there is little evidence regarding fur seal feeding habits on the rookeries except for conflicting observations made on harem bulls; the majority of the sea lion rookery population fasts for a few days only, during pupping; harbour seals on the Skeena River appear to fast for at least part of June. There is no evidence of interspecific competition between the three species studied on the British Columbia coast. Sea lions and harbour seals each year eat an estimated amount equivalent to 1.6% of the annual commercial salmon catch and 2.7% of the annual commercial herring catch. Predation at this level is believed to be of negligible importance in the reduction of existing salmon and herring stocks. Insufficient data from waters greater than 35 miles from shore precludes an assessment of fur seal predation upon ocean salmon. Further offshore collections should be made. / Science, Faculty of / Zoology, Department of / Graduate

The mechanisms of osmotic and ionic regulation in marine mammals are of interest because of the apparent lack of "fresh" water in their environment. Previous investigation on the harbor seal, (Phoca vitulina, L.), generally indicated that the seal can obtain all the water it requires from its food. However, some dispute still exists as to whether the seal may ingest sea water along with its food and conserve water by concentrating ions and excreting them with a net water gain. The effects of a 16-hour period with no fluids and also of intubation with varying amounts of distilled water and varying amounts and concentrations of sea water were determined. The concentrations of sodium, chloride and potassium ions as well as the osmotic pressures of plasma and urine were measured for the periods before and after intubation. The results of this study are discussed with respect to published data and proposed mechanisms of osmotic and ionic regulation by the kidney. The findings indicate, as suggested by others, that the seal does not gain any substantial amount of water from sea water ingestion. / Science, Faculty of / Zoology, Department of / Graduate

Gross and histological analyses of reproductive tracts from multiparous, nulliparous, and non-pregnant females of Pribilof Islands (eastern Pacific) origin have been used to determine the histology and physiology of the estrus cycle, the age of sexual maturity, and certain causes of prenatal mortality. The ovaries alternate in function, one ovary ovulating in one breeding season, the opposite ovary ovulating in the next. An undetermined factor suppresses follicular development in the ovary containing a corpus luteum of pregnancy; suppression maintains for 6 months after parturition. Graafian follicular development is greatest in July, with an average 15 follicles in the ovary destined to ovulate. About 4 of these will enlarge abruptly prior to ovulation; one will reach ovulation size (10 mm or greater in diameter) and rupture; the rest will become atretic. Mating occurs 3-5 days after parturition in mid-July. If fertilization is accomplished, the resulting blastocyst remains free in the uterus until early or mid-November, when it implants in the mucosa. The newly formed corpus luteum is actively secretory for a month after ovulation. During this time, follicular development is suppressed in both1 ovaries, and the uterine mucosa is progesteronic. From the end of August, the corpus luteum is regressive; the luteal cells are vacuolated, and secretion is minimal. This is reflected in a recrudescence of follicular activity in the ovary containing the corpus luteum, and regression of the associated uterine mucosa. Immediately prior to implantation the corpus luteum resumes secretion, and the mucosa is prepared for implantation. Placentation is established during December. Luteal degeneration begins in January and is progressive until parturition, when the corpus luteum appears to be non-secretory. Luteal degeneration has no affect on the pregnant uterine horn; it is assumed that the placenta secretes sufficient hormone to replace the luteal hormones. Prenatal mortalities take 3 forms: "missed” pregnancies, abortions, and resorptions. On the basis of histological examinations, "missed" pregnancies are ultimately due to failure of implantation. Three conditions are responsible: failure of fertilization, failure of implantation, or malfunction of the reproductive tract which precludes pregnancy. Abortion results in the expulsion of a conceptus from the uterus before term; resorption is a gradual process of dissolution of the conceptus within the uterus. On the basis of histological evidence, three causative agents of abortion and resorption are evident: degeneration of the corpus luteum after implantation, malfunction of the uterine mucosa, and intra-uterine mortality of the conceptus. Annovulatory cycles, dominated by Follicle Stimulating Hormone, occur among females 1 to 3 years of age. A cycle increasingly dominated by Luteinizing Hormone and culminating in ovulation occurs among the majority of 4-year-old females. The follicular cycle resulting in the first ovulation is later than subsequent cycles; the peak of first ovulations occurs around August 25th. On the basis of gross examinations, 60% of females ovulate for the first time at 4 years of age. Since the pregnancy rates of 5-year-old females are consistently about 50%, probably a number of 4-year-olds do not mate, either because ovulation occurs after the breeding season, or because breeding males are not available. Gross and histological analyses of reproductive tracts from nulliparous females of Robben and Commander Islands (western Pacific) origin have been used to compare the reproductive potential of two breeding populations of fur seals,; Pregnancy rates among females 4 years of age of Robben and Commander Islands origin are approximately 50%; those of 4-year old-females of Pribilof Islands origin are approximately 5%. The disparity in the age of reproductive maturity between females of the two populations is based on a physiological delay of one year in the maturation of the endocrine system controlling reproduction among females of Pribilof Islands origin. / Science, Faculty of / Zoology, Department of / Graduate

The structural and functional organization of the pinniped eye, as represented by the harbour seal, Phoca vitulina, is much more complex than previously realized. The retina of the harbour seal is similar to that of the harp seal, in that it shows little zonation of the inner nuclear layer, possesses large horizontal cells, and has similar nuclear densities within the different retinal layers throughout the retina. The outer nuclear layer is the thickest of all the retinal layers. Photoreceptor cells of types B and C were observed with a ratio of roughly 1:23 respectively. This ratio and photoreceptor density along with a well-developed and extensive tapetum, indicates a highly light-sensitive retina. The existence of retinal folding in marine mammals is also questioned and discussed. Refractive observations obtained through retinoscopy show that the harbour seal eye is very myopic and astigmatic in air, and hypermetropic with no discernable astigmatism in water. The axis of least corneal curvature is horizontal; current theories predict that the stenopeic pupil would thus correct for astigmatism in air. The functional significance of the astigmatism, which is in the order of 7 to 13 diopters, has not been adequately determined to date, however. These observations are in agreement with those recently reported for the harp seal. Behavioural studies have also confirmed the high sensitivity of the harbour seal eye to light, as suggested by the histological observations. Two captive harbour seals were trained to select a two-bar pattern over a one-bar pattern in both air and water, discriminating for the presence of a gap. Their abilities to carry out this task were measured as the gap in the two-bar pattern was gradually reduced in size. The light intensity of the white parts of the stimulus cards was 284-369 candela/m² . Under these conditions, the harbor seal can detect a gap as small as 1 mm at a distance of 1.7 m in both air and water. These studies fail to provide values of the visual acuity of the harbour seal in the strict sense, however, owing to the physics of the pattern utilized. Rather, they indicate a measure of the absolute sensitivity of the eye to light. / Science, Faculty of / Zoology, Department of / Graduate

Thesis (Ph. D.)--Faculty of Veterinary Science, University of Sydney, 2007. / Title from title screen (viewed 13 January 2009). Submitted in fulfilment of the requirements for the degree of Doctor of Philosophy to the Faculty of Veterinary Science. Degree awarded 2007; thesis submitted 2006. Includes bibliographical references. Also available in print form.

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This thesis documents the results of high pressure testing of hole-pattern annular gas seals conducted at the Texas A&M University's Turbomachinery Laboratory. The testing conditions were aimed at determining the test seals sensitivity to pressure ratio, inlet fluid preswirl, rotor speed, and rotor to seal clearance. The rotordynamic coefficients showed only small changes resulting from the different pressure ratios tested. Only the damping terms at the lower frequencies showed some influence. One other notable result from the testing of different pressure ratios is that the seals were tested in a choked flow condition, and there was not a significant change in the seal behavior when the seals transitioned to the choked condition. The inlet fluid preswirl only had a notable effect on the cross-coupled stiffness in the larger clearance tests. These results lead to the conclusion that a swirl brake could have some rotordynamic value, but only if the seals have sufficiently large clearance. Conversely this also means that if hole-pattern seals are being implemented with a small clearance, then a swirl brake would not be an effective way to improve the rotordynamic stability of the system. The only significant effect that the rotor speeds had on the rotordynamic coefficients were that the cross-coupled coefficients increased as the rotor speed increased. This is the expected result because as the rotor speed increases there is a greater shear force on the gas as it passes through the seal resulting in more fluid circumferential velocity, which results in stronger cross-coupled coefficients. The changes in clearance resulted in drastic changes in the magnitude of the coefficients. The smaller clearance yielded much higher coefficients than the larger clearance. All of the rotordynamic coefficients were predicted well by ISOTSEAL. The code was found to do a good job predicting the seal leakage as well. This gives more credence to the coefficients and leakage that ISOTSEAL predicts.

Labyrinth seals are widely used in various turbo machines including turbines, compressors and pumps. Their purpose is to prevent the backflow of the working fluid. This backflow is due to the leakage of the seal. This loss affects the efficiency of the turbo machine, so it becomes critically important to assess the leakage of the seals under the given operating conditions. The accuracy of prediction of leakage is also important for performing rotodynamic analysis. The geometric shape of the seal plays an important role in influencing the fluid flowing through the seals and the leakage rate. Many empirical seal leakage prediction models, useful from a design/analysis point of view, have been developed. Saikishan Suryanarayanan and Gerald. L .Morrison studied the influence of various geometric and flow parameters on the leakage of labyrinth seals with rectangular cavities. They proposed a leakage equation based on their Computational Fluid Dynamics (CFD) simulations using software FLUENT. However, many real world labyrinth seals do not have simple rectangular cavities. In particular, this thesis focuses on seals with Isosceles triangle shaped teeth, right triangle shaped teeth, and a NASA seal. In the present work, CFD simulations of labyrinth seals with advanced cavity shapes are performed and the results are compared with the predictions of the rectangular seal model. The results show that the advanced cavities like, Isosceles shaped seal were more efficient as compared to rectangular seals. The pressure drop, which was taken as one of the key parameters to adjudge the efficiency of seals showed negative behavior in some of the advanced cavity shaped seal. The advanced cavity shaped seals are used in various turbo machinery equipments like steam and gas turbines. This study shows that Isosceles cavity shaped seals are the most efficient among all the advanced cavity shapes used in the present study.

published_or_final_version / abstract / toc / Fine Arts / Master / Master of Philosophy