Thesis (Ph. D.)--University of California, Davis, 2002. / Includes bibliographical references. Also available via the World Wide Web. (Restricted to UC campuses).

Conventional methods for health assessment of wild-caught and stranded seals were used to describe the disease status of harbor seals in California. Clinical chemistry, infectious disease prevalence, immune function, and contaminant data were collected to evaluate harbor seal health with data collected from three groups of seals. Wild-caught seals of all ages were sampled at two locations: San Francisco Bay (a heavily urbanized estuary) and Tomales Bay (a less developed control site). Stranded seals entered rehabilitation from a more extensive portion of the California coast which included the locations where seals were caught. Hematology reference intervals were generated to provide a baseline for health assessment among the seals. Individual variability in blood variables among seals was affected by age, sex, location, and girth. Disease surveillance focused on pathogens known to cause lesions in harbor seals, zoonoses, and those with terrestrial sources. Specific pathogens of interest were E coli, Clostridium perfringens, Vibrio spp, Campylobacter spp, Salmonella, Giardia, Cryptosporidium, avian influenza virus, Brucella, Leptospira spp., Toxoplasma gondii, Sarcocystis neurona, and Neospora caninum, Leptospira spp, and phocine and canine distemper virus. There was evidence of exposure to all pathogens except for phocine distemper virus. Simple measures of immune response were used to evaluate the immune function of harbor seal pups in rehabilitation that had evidence of previous bacterial infection. The swelling response to a subcutaneous injection of phytohemagglutinin (PHA) was positively associated with growth rate, possibly illustrating the energetic trade-offs between growth and immunity. Blubber contaminant concentrations (PCBs, DDTs, PBDEs, CHLDs, and HCHs) in harbor seal pups were grouped by extent of suckling and strand location. The ratio of PCB:DDT was increased in San Francisco Bay and decreased in Monterey Bay compared with other locations along the coast. Pups that weaned in the wild, lost weight and then stranded had the highest contaminant levels, equivalent to the concentrations detected in stranded adult harbor seals. Dispersal and survival were monitored by satellite telemetry in harbor seal pups released from rehabilitation and recently weaned wild-caught pups to assess the effect of condition, health, and contaminant levels on survival probability. Increased contaminant levels and decreased thyroxine (T4) were associated with decreased survival probability. Increased mass, particularly among the rehabilitated pups, was associated with increased survival probability. This study demonstrates that health and survival of harbor seals pups along the central California coast are impacted by human activities such as contaminant disposal, pathogen pollution and boat traffic, although the variability in individual health measures requires carefully designed studies to detect these effects.

Thesis (M. Sc.), Memorial University of Newfoundland, 1999. / Bibliography: p. 169-179.

No description available.

It has been assumed that the considerable dispersal ability of many marine species would prevent genetic divergence in the absence of geographic isolation. However, recent work has shown that many marine species often develop differentiation among areas within their known dispersal range. This 'paradox' of marine divergence is particularly important among marine mammal species where behavior can restrict gene flow. To investigate genetic substructure within such a species, I used tissue samples collected from 63 stranded Pacific harbor seals (Phoca vitulina richardsi) in Washington and Oregon between 2006 and 2010 for population stock analysis. DNA was extracted from frozen tissues, and a 551 bp fragment of mtDNA control region sequence and eight microsatellite loci were amplified to investigate localized genetic structure. Minimum spanning network and haplotype frequency analyses of mtDNA sequences indicated that while haplotype lineages are not isolated within a sampling region, there is some evidence of regional differentiation. On the other hand, microsatellite data suggest a lack of substructure among the animals sampled, with only a weak signal of limited gene flow between Puget Sound and coastal areas. Biased dispersal among age classes was also suggested, with juveniles showing less differentiation among areas than adults. Regardless of the historical scenario which has led to this complex pattern of genetic structure in Pacific harbor seals across the Pacific Northwest, my results suggest higher levels of exchange among areas than previously suspected, and will have important consequences for future management considerations for these stocks.

Understanding the movement behavior and foraging strategies of individuals across multiple spatial and temporal scales is essential not only for understanding the biological requirements of individuals but also for linking individual strategies to population level effects. Glacial fjords scattered throughout south-central and southeastern Alaska host some of the largest seasonal aggregations of harbor seals (Phoca vitulina richardii) in the world, and an estimated 15% of the harbor seal population in Alaska is found seasonally at these glacial ice sites. Over the last two decades, the number of harbor seals has declined at two of the primary glacial fjords, in Aialik Bay in south-central Alaska and in Glacier Bay in southeastern Alaska, thus raising concerns regarding the viability of seal populations in glacial fjord environments. From 2004-2009, the foraging ecology, diving behavior, and migration patterns of harbor seals from Glacier Bay National Park, Alaska were examined in relation to prey availability and oceanographic features in Glacier Bay and the surrounding regions of southeastern Alaska. Time-depth recorders, very high frequency transmitters, and satellite-linked transmitters were used to quantify the vertical and horizontal movement patterns of harbor seals in the marine environment. Specifically, (1) I characterized the diving behavior, foraging areas, and foraging strategies of female harbor seals from terrestrial and glacial ice sites relative to prey availability during the breeding season (May-June) in Glacier Bay, (2) I quantified the intra-population variation in at-sea post-breeding season (September-April) distribution and movement patterns of female harbor seals in relation to oceanographic features, (3) I quantified the post-breeding season migration patterns of female harbor seals relative to the boundaries of the marine protected area of Glacier Bay National Park, and (4) I characterized the use of the continental shelf region of the eastern Gulf of Alaska by female harbor seals from Glacier Bay, both as a foraging area and as a migratory corridor in relation to oceanographic features. During the breeding season, there was a substantial degree of intra-population variation in the diving behavior and foraging areas of juvenile and adult female seals from glacial ice and terrestrial sites in Glacier Bay. The presence of multiple diving strategies suggests that differences in the relative density and depth of prey fields in glacial ice and terrestrial habitats in addition to seal age and reproductive status may influence diving and foraging behavior of harbor seals. During the post-breeding season, juvenile and adult female harbor seals ranged extensively beyond the boundaries of the marine protected area of Glacier Bay National Park, throughout the northern inshore waters of southeastern Alaska and the continental shelf region of the eastern Gulf of Alaska between Cross Sound and Prince William Sound, Alaska (up to 900 kilometers away). Seals exhibited a relatively high degree of intra-population variation in their at-sea post-breeding season distribution patterns that may be a function of extrinsic factors such as oceanographic characteristics, which can influence prey availability as well as intrinsic factors including previous experience with foraging areas and seal condition and age. Use of the continental shelf region of the eastern Gulf of Alaska by harbor seals as a foraging area may be due to enhanced biological productivity which may be associated with ephemeral hydrographic and/or static bathymetric features. Despite extensive migrations of seals from Glacier Bay during the post-breeding season, there was a high degree of inter-annual site fidelity of seals to Glacier Bay the following breeding season after seals were captured. / Graduation date: 2012

Persistent organic pollutants (POPs) have been contaminating the marine environment since the mid 2Oth Century and continue to do so today. The polychlorinated biphenyls (PCBs) are of particular concern, since they are found at high concentrations in marine mammals throughout the Northern Hemisphere, and have been associated with endocrine disruption, reproductive impairment, immunotoxicity, and outbreaks of disease. In this study, samples were obtained from free-ranging harbour seal (Phoca vituilna) pups, which were live-captured in British Columbia, Canada, and Washington State, USA, in order to assess adverse health effects associated with POPs on the immune system of these mammals. PCBs were the most abundant of the 31 POPs measured in seals, and represented the greatest toxicological concern on the basis of established reference values for laboratory rodents and aquatic wildlife consumers. Seal immune function was assessed using traditional measures of immunotoxicity, including hematology, innate immune function, and adaptive immune function, and related to PCB concentrations while carefully controlling for confounding factors such as age, sex and condition. PCB concentrations negatively correlated to phagocytosis, T lymphocyte proliferative responses, (thymosin-a1-induced) lymphocyte signalling, and lymphocyte counts, and positively associated with the respiratory burst of phagocytes and aryl hydrocarbon receptor (AhR) expression of white blood cells, suggesting chemical-associated immunotoxicity. Parallel experiments, in which harbour seal white blood cells were exposed in vitro to 2,3,7,8-tetrachlorodibenzo-p-dioxin, a potent immunotoxicant, further supported the hypothesis that the observed reduction in immunocompetence in free-ranging seals may be due to an AhR-mediated mechanism of immunotoxicity. Principal component analysis (PCA) of immunological endpoints combined evidence of PCB-associated effects on the immune system as a whole. However, PCA also identified a difference between the immunological profiles of urban seals and those from remote sites, consistent with elevated pathogen abundance due to biological pollution at urban sites. In a second approach, PCB concentrations were related to concentrations of vitamin A and expression levels of its receptor, the retinoic acid receptor alpha (RARa), which are known to be sensitive to PCB exposure. More contaminated seals were characterised by lower vitamin A concentrations in circulation and in the blubber, as well as higher RARa expression in the blubber. AhR expression and concentrations of thymosin-a1 (a thymic hormone important in lymphocyte development and immune function) did not relate to contaminants when their levels were investigated in seal tissues (blubber, skin), contrasting their sensitivity in white blood cells. These results implied that PCB-associated toxicity may be reflected if a biomarker represents a primary lesion, but might not be extrapolated among tissues in all cases. Secondly, although blubber represents the primary site of PCB storage, it is not necessarily the site of the highest toxicity. In summary, significant evidence of immunotoxicity and disruption of immune function-related biomarkers has been provided in a healthy group of free-ranging marine mammals which contributes to the weight of evidence that environmental contaminants may render marine mammal populations more vulnerable to disease through immunotoxicity. Immune function measures in free-ranging harbour seal pups exposed to contaminants in vivo, in combination with harbour seal white blood cells in vitro, furthermore suggested that immunotoxicity may take place through an AhR-mediated mechanism of action. An unexpected finding was the evidence of a second, independent, impact on the immune system of seals, consisting of biological pollution. The combination of both chemical and biological pollution, that would imply both diminished immune responses and increased pathogen loads, may represent the largest threat to the health of marine mammals in many parts of the world.

No description available.

No description available.

Thesis (Ph. D.)--Joint Program in Applied Ocean Science and Engineering (Massachusetts Institute of Technology, Department of Mechanical Engineering; and the Woods Hole Oceanographic Institution), 2015 / This electronic version was submitted by the student author. The certified thesis is available in the Institute Archives and Special Collections. / Cataloged from student-submitted PDF version of thesis. / Includes bibliographical references (pages 183-193). / This thesis is motivated by a series of biological experiments that display the harbor seal's extraordinary ability to track the wake of an object several seconds after it has swum by. They do so despite having auditory and visual cues blocked, pointing to use of their whiskers as sensors of minute water movements. In this work, I elucidate the basic uid mechanisms that seals may employ to accomplish this detection. Key are the unique ow-induced vibration properties resulting from the geometry of the harbor seal whisker, which is undulatory and elliptical in cross-section. First, the vortex-induced vibration (VIV) characteristics of the whisker geometry are tested. Direct force measurements and ow visualizations on a rigid whisker model undergoing a range of 1-D imposed oscillations show that the geometry passively reduces VIV (factor of > 10), despite contributions from eective added mass and damping. Next, a biomimetic whisker sensor is designed and fabricated. The rigid whisker model is mounted on a four-armed flexure, allowing it to freely vibrate in both in-line and crossflow directions. Strain gauges on the flexure measure deflections at the base. Finally, this device is tested in a simplified version of the sh wake { seal whisker interaction scenario. The whisker is towed behind an upstream cylinder with larger diameter. Whereas in open water the whisker exhibits very low vibration when its long axis is aligned with the incoming ow, once it enters the wake it oscillates with large amplitude and its frequency coincides with the Strouhal frequency of the upstream cylinder. This makes the detection of an upstream wake as well as an estimation of the size of the wake-generating body possible. A slaloming motion among the wake vortices causes the whisker to oscillate in this manner. The same mechanism has been previously observed in energy-extracting foils and trout actively swimming behind bluff cylinders in a stream. / by Heather Rachel Beem. / Ph.D.