Thesis (M.S.)---University of North Carolina Wilmington, 2008. / Title from PDF title page (viewed September 22, 2008) Includes bibliographical references (p. 45-50)

No description available.

Thesis (Ph.D.) - University of St Andrews, May 2007.

Thesis (M.Sc.)--Memorial University of Newfoundland, 1997. / Restricted until June 1998. Bibliography: leaves [82]-93.

Underwater gliders can provide an alternative cost-effective platform for passive acoustic monitoring surveys, compared to boat surveys, for abundance estimation and to collect high resolution environmental data for habitat studies. Gliders are usually equipped with one acoustic sensor, which limits the methods available for abundance estimation from acoustic data. Estimation of parameters used in distance sampling methodology, such as the detection function and cue rates, must be estimated separately from the glider deployment. A methodology for deriving the acoustic detection function of vocal animals is demonstrated in chapter 2 with a combined biologging and passive acoustic experiment. The methodology consists of distance estimation of the clicks produced by the tagged animal and detected at acoustic receivers placed at different depths, using surface bounce detections to estimate range. In addition, different detection algorithms were tested for the detectability of Blainville's beaked whales. Detectability was found to vary with depth for Blainville's beaked whales in the area of El Hierro (Canary Islands). The depth dependent detectability for this species was tested further in chapter 3 with a wider dataset from two different geographic populations of Blainville's beaked whales, those of El Hierro and the Bahamas. Differences in detectability were found using depth and animal movement data as recorded on the DTAG in a simulated network of receivers placed at different depths. In addition, sequences of clicks, called click scans, were tested as an additional “cue” for cue counting methodology. The high directionality of beaked whale regular clicks leads to reduced detection ranges for receivers close to the surface or for receivers placed much deeper than the foraging depths of the wales and this reduction translates into varying lengths and numbers of detected click clusters as a function of distance and receiver depth. Chapter 4 presents a method for estimating density of animals from underwater gliders and tests the method in a simulated glider survey using different distribution and density scenarios using clicks and click scans as cue for density estimation.

Please read the abstract in the section 00front of this document / Dissertation (MSc (Zoology))--University of Pretoria, 2006. / Zoology and Entomology / unrestricted

Thesis (M.S. in Meteorology and Physical Oceanography)--Naval Postgraduate School, June 2004. / Thesis advisor(s): Ching-Sang Chiu, Curtis A. Collins. Includes bibliographical references (p. 43-44). Also available online.

While the impact of top-down and bottom-up drivers of ecosystem functions has been given considerable argument, here the mid-trophic level is given focus. In marine systems the influence of mid-trophic level species operates in a ‘wasp-waisted’ structure, where they exert regulatory control by acting as a valve to energy flow between large seasonal pulses of primary production and upper level species. In this study I examine the impact of foraging eastern Pacific gray whales (Eschrichtius robustus) on mysid species at the ‘wasp-waist’ (Order Mysidacea), and vice versa, at feeding sites in Clayoquot Sound off the west coast of Vancouver Island. I appraise previously unknown aspects of the ‘prey-scape’, and further explore life-history traits that allow prey populations to persist in a given species array. The set of problems that I examine are all based on the whales’ top-down forcing in a localized area, and the prey response. I use several scales of observation as dictated by the nature of each question. I examine top down forcing and subsequent prey switching over a 25-year period, the variation in foraging intensity over a 15 year period, the differential prey species’ response to persistent predatory pulses that creates dominance and diversity among the mysid species flock, and whales’ within-season response to possible satiation. Each of these studies is linked by the common goal of illuminating the intimate relationship between predator and prey. Gray whale foraging has decimated amphipod prey resources in the study area past the point of recovery over the last 25 years, and the prey resource is no longer a viable energy source. This has led to the abandonment of benthic-feeding by gray whales in the area, and a switch to mysids as a primary prey source. It is in investigating these mysid species’ ability to rebound following severe foraging pressure that I uncovered two principal life history strategies, one held by the single dominant mysid species, and another used by 9 or 10 others consistently sampled. The capacity for renewal of mysid swarms is imperative if Clayoquot Sound is to persist as a productive foraging area for gray whales. The pattern of this relationship that I present, based on a 15 year span, was previously unknown. Intense foraging of mysids by gray whales during a summer affects the reserves for the following season, leading to a biennial fluctuation in the number of whales the area can sustain, although some of the heaviest foraging seasons require several years to show mysid recovery. I state 9 or 10 other species, as through the intense examination of mysids here, there may be a new species designated. The data gathered by myself and colleagues over the past 25 years that whales have been studied in Clayoquot Sound, clearly shows that predation by baleen whales can affect the future quality of their foraging areas, as well as influencing the population, life-stage and diversity of prey species. My work furthers knowledge in life history characteristics of the mysid species present in the study area, particularly growth and reproduction, and ability to capitalize on a release of predation pressure over winter to recover. That, in turn creates a series of following questions about how different life history strategies make use of a variety of possible energy pathways to stabilize ecosystems at least at discrete spatial scales. / Graduate

Thesis (Ph. D.)--University of California, San Diego, 1997. / Vita. Includes bibliographical references.

The purpose of this study is to explore the implications of the historical perspective when it is linked to the ecological concept of adaptive management. The vehicle for this exploration is a genetically distinct population of killer whales (Orcinus orca), whose core coastal habitat includes the inland waters of Georgia Strait, Juan de Fuca Strait and Puget Sound; a geographic region referred to as the “Salish Sea.” This stock of killer whales, known as the Southern Resident Community, is unique in having a detailed scientific record that spans over two decades and recently this population was listed as “threatened” by the Committee on the Status of Endangered Wildlife in Canada (April 1999). The goal of this study is to take account of the specific ecological history of this killer whale population, and provide an assessment of the resiliency of this stock to withstand present levels of human impacts. In Chapter 1 the academic concepts of historical ecology and adaptive management are reviewed in preparation for their application as theory. Chapter 2 is an inventory of the ecological domain, in which the focal population is assessed by temporally measurable indicators o f its ecological status: population dynamics, feeding ecology, and habitat use. In Chapter 3 temporally measurable indicators of stress such as predation, disease, food resource depletion, toxic exposure, surface disturbance, and underwater noise are examined for their impact upon the carrying capacity of the environment of the whales. Chapter 4 plots both sets of indicators historically as trends in variation from the Sample Mean at different time scales (months, years, decades, centuries), and indexes them in terms of perturbations from the historical norm. In Chapter 5 four basic types of historical trends in environmental impacts are identified that are directly relevant to evaluating the resilience of the management unit. These are: (1) Relic impacts - potential impacts that are no longer present, but may account for present conditions. (2) Adapted impacts - potential impacts that have been around long enough for the management unit to have adapted to them. (3) Cumulative impacts- potential impacts that accumulate slowly in the environment or life history of the management unit before exerting environmental resistance. (4) New impacts - potential impacts with which the management unit has not had previous experience. These four historical criteria allow the manager to identify the most sensitive impacts for present conditions, and identify scales of management for restorative intervention. This resiliency index should have application for most types of ecological systems, or management units, because it describes very generalized types of temporal outcomes, independent of scale and life history pattern of the management unit. In terms of the focal population of killer whales in this study, the historical assessment suggests that: 1) these whales are presently a remnant population due to killing and capture by European settlers from the turn of the century to the 1970s; 2) they have bio-accumulated toxins during the highest historical periods of environmental pollution in the Salish Sea, and this toxic exposure will continue to increase for the whales over the next few decades; 3) this killer whale population has never previously experienced a lack of salmon, so diminishing salmon stocks are potentially a new stress on them; and 4) these killer whales have adapted to vessel traffic and noise for several decades in relation to vessel-based salmon fishing operations, and that this influence has recently been replaced by record levels of whale watching traffic, which potentially poses more severe impacts than fishing vessels because the boats follow the whales, rather than their prey. This historical assessment facilitates the application of “adaptive management” strategies for these whales by providing the basis for predicting the current “resiliency” of this population to adapt to environmental conditions. / Graduate