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

The western North Pacific population of gray whales (Eschrichtius robustus) is critically endangered of extinction. The population size is estimated to be 131 individuals with 31 reproductive females. Throughout their potential home range, the western gray whale population face several threats to their future survival. On their only known feeding grounds off the northeastern coast of Sakhalin Island, Russia, anthropogenic activity has increased in the past decade due to oil and gas exploration and platform/pipeline construction. This dissertation examines the influences of geophysical seismic surveys (pulse sounds) and platform/pipeline installation (continuous sounds). Each chapter progressively improves upon behavioral models that assess changes in gray whale movements and respirations relative to anthropogenic activity. Theodolite tracking and focal follow methodologies were employed to collect gray whales' movement and respiration information during and in the absence of anthropogenic activity. Spatial, temporal, environmental, and acoustic (pulse and/or continuous) sound levels and non-sound related anthropogenic variables were included as explanatory variables to examine their influence on movement and respiration response variables, such as speed, orientations, dive/surface time, breathing rates, etc. During the 3-D seismic activity, gray whales traveled faster, changed directions of movement less, were recorded farther from shore and stayed underwater longer between respirations as the received sound level exposure increased. During platform/pipeline installations, western gray whales increased their distance from shore with indicators of stress (rapid breathing) and observed to be sensitive to close distance of approach by vessels. No acoustic influence on western gray whale behavior was found during a 4-D seismic survey; however, sample sizes were small in this study to sufficiently detect more subtle to moderate changes in gray whale behavior. These studies illustrate short-term influences anthropogenic activity had on western gray whale behavior which could lead to longer-term responses that may be detrimental to the survival of certain individuals and/or the population. A comprehensive analyses are proposed to increase sample sizes to identify subtle to moderate behavioral changes as well as examine alternative hypotheses to the null hypothesis of no impact used in this dissertation. With the potential to displace individuals/population out of critical feeding habitats needed for their annual survival and the expected increase of anthropogenic activity in the future, this dissertation highlights the importance to monitor and identify problems and suggest alternatives to development/activities that may be impacting this endangered population of gray whales.

The western population of gray whales (Eschrichtius robustus) is endangered with approximately 130 individuals remaining. Many individuals return annually to the same feeding sites off northeastern Sakhalin Island, indicating a site-specific dependence to this geographic area. This apparently critically important habitat is especially vital for nursing females and their calves, as female energetic requirements are increased during lactation, and calves need to be ready to separate and begin to feed on their own. This study focuses on movements, respirations and behavioral patterns of mother/calf pairs on their feeding ground, with data collected during summer-autumn of 2002-2009. Shore-based observations included three methods: theodolite tracking, focal-animal behavior sampling, and photo-identification. Whales were categorized as three groups of individuals: mother/calf pairs, weaned calves, and other individuals. Analyses were performed to assess differences between groups of individuals, and in relation to their behavior. The null hypothesis of the study was that there were no differences in movement/respiration/behavioral patterns and habitat use between different groups of individuals. Results did not support this hypothesis. Significant differences in movements and respirations were found for certain groups of individuals. These differences also varied in relation to the whales' behavioral activity (feeding, feeding/traveling, and traveling). The shore-based photography was used to obtain additional information on individuals (especially mother/calf pairs) and their sightings, as well as to evaluate the success of this approach. A total of 144 individuals, including 10 females (sighted with calves) and 31 calves were identified during 2004-2009. The shore-based photo-identification approach was successful, and due to being a non-invasive technique, is recommended as a supplemental approach to vessel-based photo-ID efforts. Reproductive success and survival of western gray whales are concern especially due to the presence of industrial activity in the area, as well as recently increased mortalities of female gray whales off Japan. Therefore, the results of this study indicate the importance of considering differences in needs and habitat utilization of different groups of individuals for basic science information as well as for management purposes of protection of western gray whales.

Gray whales (Eschrichtius robustus Lilljeborg) forage predominantly on hyper-benthic mysids (Mysidae) along the southwest coast of Vancouver Island, British Columbia. The role of mysids in the abundance and distribution of foraging gray whales prompted interest in this study. I relate the inter- and intra-annual foraging behaviour of gray whales to the number of mysid patches and biomass through boat based surveys of foraging whales, and the application of acoustic techniques for estimating mysid prey. I examine the spatial pattern of foraging gray whales and the 10 m isobath. The abundance and distribution of mysid patches are more common at a water depth of 10 m, and the likely mechanism driving the spatial pattern between foraging gray whales and the 10 m isobath. I examine whale abundance and distribution patterns during three consecutive foraging seasons. More whales forage in years when mysid prey are more abundant, and mysid patches are of larger size and higher in biomass. Whales have a considerable top-down effect on mysid populations. Years of heavy whale predation depletes mysid stocks. Mysid populations tend to increase in years of low whale activity. I examine whale abundance and distribution patterns of habitat use during a foraging season along the southwest coast of Flores Island and Nootka Sound. The abundance of mysid patches and biomass in Nootka Sound does not influence the whales’ use of Flores Island; rather the whales exploited both areas concurrently. This study expands the understanding of gray whale habitat use along the southwest coast of Vancouver Island, British Columbia.

Gray whales (Eschrichtius robustus Lilljeborg) forage predominantly on hyper-benthic mysids (Mysidae) along the southwest coast of Vancouver Island, British Columbia. The role of mysids in the abundance and distribution of foraging gray whales prompted interest in this study. I relate the inter- and intra-annual foraging behaviour of gray whales to the number of mysid patches and biomass through boat based surveys of foraging whales, and the application of acoustic techniques for estimating mysid prey. I examine the spatial pattern of foraging gray whales and the 10 m isobath. The abundance and distribution of mysid patches are more common at a water depth of 10 m, and the likely mechanism driving the spatial pattern between foraging gray whales and the 10 m isobath. I examine whale abundance and distribution patterns during three consecutive foraging seasons. More whales forage in years when mysid prey are more abundant, and mysid patches are of larger size and higher in biomass. Whales have a considerable top-down effect on mysid populations. Years of heavy whale predation depletes mysid stocks. Mysid populations tend to increase in years of low whale activity. I examine whale abundance and distribution patterns of habitat use during a foraging season along the southwest coast of Flores Island and Nootka Sound. The abundance of mysid patches and biomass in Nootka Sound does not influence the whales’ use of Flores Island; rather the whales exploited both areas concurrently. This study expands the understanding of gray whale habitat use along the southwest coast of Vancouver Island, British Columbia.