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Geology topics

Glenn R. VanBlaricom

Publications and source records attributed to Glenn R. VanBlaricom.

18 recordsLinked to original sources
USGS2015

The relationship between vessel traffic and noise levels received by killer whales ( Orcinus orca )

Whale watching has become increasingly popular as an ecotourism activity around the globe and is beneficial for environmental education and local economies. Southern Resident killer whales ( Orcinus orca ) comprise an endangered population that is frequently observed by a large whale watching fleet in the inland waters of Washington state and British Columbia. One of the factors identified as a risk to recovery for the population is the effect of vessels and associated noise. An examination of the effects of vessels and associated noise on whale behavior utilized novel equipment to address limitations of previous studies. Digital acoustic recording tags (DTAGs) measured the noise levels the tagged whales received while laser positioning systems allowed collection of geo-referenced data for tagged whales and all vessels within 1000 m of the tagged whale. The objective of the current study was to compare vessel data and DTAG recordings to relate vessel traffic to the ambient noise received by tagged whales. Two analyses were conducted, one including all recording intervals, and one that excluded intervals when only the research vessel was present. For all data, significant predictors of noise levels were length (inverse relationship), number of propellers, and vessel speed, but only 15% of the variation in noise was explained by this model. When research-vessel-only intervals were excluded, vessel speed was the only significant predictor of noise levels, and explained 42% of the variation. Simple linear regressions (ignoring covariates) found that average vessel speed and number of propellers were the only significant correlates with noise levels. We conclude that vessel speed is the most important predictor of noise levels received by whales in this study. Thus, measures that reduce vessel speed in the vicinity of killer whales would reduce noise exposure in this population.

Vancouver, Washington↗
USGS2015

Predictive modelling of habitat use by marine predators with respect to the abundance and depth distribution of pelagic prey

Understanding the ecological processes that underpin species distribution patterns is a fundamental goal in spatial ecology. However, developing predictive models of habitat use is challenging for species that forage in marine environments, as both predators and prey are often highly mobile and difficult to monitor. Consequently, few studies have developed resource selection functions for marine predators based directly on the abundance and distribution of their prey. We analysed contemporaneous data on the diving locations of two seabird species, the shallow-diving Peruvian Booby ( Sula variegata ) and deeper diving Guanay Cormorant ( Phalacrocorax bougainvilliorum ), and the abundance and depth distribution of their main prey, Peruvian anchoveta ( Engraulis ringens ). Based on this unique data set, we developed resource selection functions to test the hypothesis that the probability of seabird diving behaviour at a given location is a function of the relative abundance of prey in the upper water column. For both species, we show that the probability of diving behaviour is mostly explained by the distribution of prey at shallow depths. While the probability of diving behaviour increases sharply with prey abundance at relatively low levels of abundance, support for including abundance in addition to the depth distribution of prey is weak, suggesting that prey abundance was not a major factor determining the location of diving behaviour during the study period. The study thus highlights the importance of the depth distribution of prey for two species of seabird with different diving capabilities. The results complement previous research that points towards the importance of oceanographic processes that enhance the accessibility of prey to seabirds. The implications are that locations where prey is predictably found at accessible depths may be more important for surface foragers, such as seabirds, than locations where prey is predictably abundant. Analysis of the relative importance of abundance and accessibility is essential for the design and evaluation of effective management responses to reduced prey availability for seabirds and other top predators in marine systems.

Gulf of Guinea↗
USGS2015

Sea otters in captivity: applications and implications of husbandry development, public display, scientific research and management, and rescue and rehabilitation for sea otter conservation

Studies of sea otters in captivity began in 1932, producing important insights for conservation. Soviet (initiated in 1932) and United States (1951) studies provided information on captive otter husbandry, setting the stage for eventual large-scale translocations as tools for population restoration. Early studies also informed effective housing of animals in zoos and aquaria, with sea otters first publicly displayed in 1954. Surveys credited displayed otters in convincing the public of conservation values. After early studies, initial scientific data for captive sea otters in aquaria came from work initiated in 1956, and from dedicated research facilities beginning in 1968. Significant achievements have been made in studies of behavior, physiology, reproduction, and high-priority management issues. Larger-scale projects involving translocation and oil spill response provided extensive insights into stress reactions, water quality issues in captivity, and effects of oil spills.

Book chapter↗
USGS2015

Synopsis of the history of sea otter conservation in the United States

In the late 1860s, declining US sea otter populations elicited concern because of prior excessive harvests. Congress mandated protection of Alaskan sea otters in 1868, but hunting continued unrestrained. The Fur Seal Treaty of 1911 (abrogated in 1941) protected sea otters in international waters, but was not applicable to most sea otter habitats and failed to terminate all legal sea otter harvests. Between 1941 and 1972 only the State of California was consistently engaged in sea otter conservation, based on a 1913 state law. Trends in cultural values toward protection of species based on imperiled status rather than economics led to the Marine Mammal Protection Act (1972), giving sea otters unambiguous protection in all US territorial waters. Sea otter habitat protection by the US government began in the 1890s. State marine protected areas potentially support sea otter conservation, particularly when paired with adjacent federal protected entities in or near sea otter habitat.

Book chapter↗
USGS2015

Distribution, abundance, and habitat associations of a large bivalve (Panopea generosa) in a eutrophic, fjord estuary

Marine bivalves are important ecosystem constituents and frequently support valuable fisheries. In many nearshore areas, human disturbance—including declining habitat and water quality—can affect the distribution and abundance of bivalve populations, and complicate ecosystem and fishery management assessments. Infaunal bivalves, in particular, are frequently cryptic and difficult to detect; thus, assessing potential impacts on their populations requires suitable, scalable methods for estimating abundance and distribution. In this study, population size of a common benthic bivalve (the geoduck Panopea generosa ) is estimated with a Bayesian habitat-based model fit to scuba and tethered camera data in Hood Canal, a fjord basin in Washington state. Densities declined more than two orders of magnitude along a north—south gradient, concomitant with patterns of deepwater dissolved oxygen, and intensity and duration of seasonal hypoxia. Across the basin, geoducks were most abundant in loose, unconsolidated, sand substrate. The current study demonstrates the utility of using scuba, tethered video, and habitat models to estimate the abundance and distribution of a large infaunal bivalve at a regional (385-km 2 ) scale.

Washington↗
USGS2015

Ecological effects of the harvest phase of geoduck clam (Panopea generosa Gould, 1850) aquaculture on infaunal communities in southern Puget Sound, Washington USA.

Intertidal aquaculture for geoducks ( Panopea generosa Gould, 1850) is expanding in southern Puget Sound, Washington, where gently sloping sandy beaches are used for field culture. Geoduck aquaculture contributes significantly to the regional economy, but has become controversial because of a range of unresolved questions involving potential biological impacts on marine ecosystems. From 2008 through 2012, the authors used a “before-after-control-impact” experimental design, emphasizing spatial scales comparable with those used by geoduck culturists to evaluate the effects of harvesting market-ready geoducks on associated benthic infaunal communities. Infauna were sampled at three different study locations in southern Puget Sound at monthly intervals before, during, and after harvests of clams, and along extralimital transects extending away from the edges of cultured plots to assess the effects of harvest activities in adjacent uncultured habitat. Using multivariate statistical approaches, strong seasonal and spatial signals in patterns of abundance were found, but there was scant evidence of effects on the community structure associated with geoduck harvest disturbances within cultured plots. Likewise, no indications of significant “spillover” effects of harvest on uncultured habitat adjacent to cultured plots were noted. Complementary univariate approaches revealed little evidence of harvest effects on infaunal biodiversity and indications of modest effects on populations of individual infaunal taxa. Of 10 common taxa analyzed, only three showed evidence of reduced densities, although minor, after harvests whereas the remaining seven taxa indicated either neutral responses to harvest disturbances or increased abundance either during or in the months after harvest events. It is suggested that a relatively active natural disturbance regime, including both small-scale and large-scale events that occur with comparable intensity but more frequently than geoduck harvest events in cultured plots, has facilitated assemblage-level infaunal resistance and resilience to harvest disturbances.

Washington↗
USGS2015

Effects of geoduck (Panopea generosa) aquaculture on resident and transient macrofauna communities of Puget Sound, Washington, USA

In Washington state, commercial culture of geoducks ( Panopea generosa ) involves large-scale out-planting of juveniles to intertidal habitats, and installation of PVC tubes and netting to exclude predators and increase early survival. Structures associated with this nascent aquaculture method are examined to determine whether they affect patterns of use by resident and transient macrofauna. Results are summarized from regular surveys of aquaculture operations and reference beaches in 2009 to 2011 at three sites during three phases of culture: (1) pregear (-geoducks, -structure), (2) gear present (+geoducks, +structures), and (3) postgear (+geoducks, -structures). Resident macroinvertebrates (infauna and epifauna) were sampled monthly (in most cases) using coring methods at low tide during all three phases. Differences in community composition between culture plots and reference areas were examined with permutational analysis of variance and homogeneity of multivariate dispersion tests. Scuba and shoreline transect surveys were used to examine habitat use by transient fish and macroinvertebrates. Analysis of similarity and complementary nonmetric multidimensional scaling were used to compare differences between species functional groups and habitat type during different aquaculture phases. Results suggest that resident and transient macrofauna respond differently to structures associated with geoduck aquaculture. No consistent differences in the community of resident macrofauna were observed at culture plots or reference areas at the three sites during any year. Conversely, total abundance of transient fish and macroinvertebrates were more than two times greater at culture plots than reference areas when aquaculture structures were in place. Community composition differed (analysis of similarity) between culture and reference plots during the gear-present phase, but did not persist to the next farming stage (postgear). Habitat complexity associated with shellfish aquaculture may attract some structure-associated transient species observed infrequently on reference beaches, and may displace other species that typically occur in areas lacking epibenthic structure. This study provides a first look at the effects of multiple phases of geoduck farming on macrofauna, and has important implications for the management of a rapidly expanding sector of the aquaculture industry.

Washington↗
USGS2014

Reduced disease in black abalone following mass mortality: Phage therapy and natural selection

Black abalone, Haliotis cracherodii , populations along the NE Pacific ocean have declined due to the rickettsial disease withering syndrome (WS). Natural recovery on San Nicolas Island (SNI) of Southern California suggested the development of resistance in island populations. Experimental challenges in one treatment demonstrated that progeny of disease-selected black abalone from SNI survived better than did those from naïve black abalone from Carmel Point in mainland coastal central California. Unexpectedly, the presence of a newly observed bacteriophage infecting the WS rickettsia (WS-RLO) had strong effects on the survival of infected abalone. Specifically, presence of phage-infected RLO (RLOv) reduced the host response to infection, RLO infection loads, and associated mortality. These data suggest that the black abalone: WS-RLO relationship is evolving through dual host mechanisms of resistance to RLO infection in the digestive gland via tolerance to infection in the primary target tissue (the post-esophagus) coupled with reduced pathogenicity of the WS-RLO by phage infection, which effectively reduces the infection load in the primary target tissue by half. Sea surface temperature patterns off southern California, associated with a recent hiatus in global-scale ocean warming, do not appear to be a sufficient explanation for survival patterns in SNI black abalone. These data highlight the potential for natural recovery of abalone populations over time and that further understanding of mechanisms governing host–parasite relationships will better enable us to manage declining populations.

California↗
USGS2013

Energy cost of vessel disturbance to Kittlitz's Murrelets Brachyramphus brevirostris

We evaluated the energy cost of vessel disturbance for individual Kittlitz’s Murrelets Brachyramphus brevirostris in Glacier Bay National Park and Preserve in Alaska, USA. We used Monte Carlo simulations to model the daily energy expense associated with flight from vessels by both breeding and non-breeding birds and evaluated risk based on both the magnitude of costs incurred and the degree to which the costs may be chronic. We used two scenarios of vessel disturbance for average- and peak-vessel traffic. Because they are more likely to fly away from vessels, non-breeding birds had a greater increase in energy expenditure when disturbed (up to 30% increase under the average scenario and >50% increase under the peak scenario) than breeders (up to 10% and 30% increases under the average and peak scenarios, respectively). Likewise, non-breeding birds were more likely to experience chronic increases in energy expense (i.e. a greater percentage of days with an increase in energy expenditure) than breeding birds. Our modeling results indicated that breeding and non-breeding birds were both susceptible to fitness consequences (e.g. reduced reproductive success and survival) resulting from the energy cost.

Alaska↗
USGS2002

Food limitation and the recovery of sea otters following the 'Exxon Valdez' oil spill

We examined the potential role of food limitation in constraining the recovery of sea otters Enhydra lutris in Prince William Sound, Alaska, following the 'Exxon Valdez' oil spill. The spill resulted in the removal of a large number of sea otters in 1989, and as of 1998, the portion of the population in the heavily oiled northern Knight Island region had not fully recovered. Between 1996 and 1998, prey consumption rate was higher and the condition of sea otters was better at northern Knight Island than in an unoiled area of the sound (Montague Island). Estimates of prey energy available per unit mass of sea otter were about 4 times higher at Knight than Montague Island, albeit not significantly different between the 2 areas. Over this same period, the number of sea otters remained constant at northern Knight Island but increased at Montague Island. These data suggest that food was at least as abundant at Knight than at Montague Island, and that recovery of sea otters via intrinsic population growth was limited by factors other than food. However, the availability of food, the prey consumption rate, and the condition of sea otters were all much lower at both Knight and Montague Islands than in areas newly occupied by sea otters where the population growth rate was near the theoretical maximum. It is possible that the relatively short supply of food (compared to areas where sea otter population growth rate was high) may have inhibited immigration or interacted with other factors (e.g. oil-induced mortality or predation) to restrict sea otter population growth. Nonetheless, these data suggest that impacts of anthropogenic disturbances on large, often food-limited vertebrate predators can persist in spite of the availability of food resources that are sufficient for intrinsic population growth.

Alaska↗
USGS2002

Sea otter ( Enhydra lutris ) perspective: Part B. Food limitation and the recovery of sea otters following the Exxon Valdez oil spill

We examined the potential role of food limitation in constraining recovery of sea otters in Prince William Sound, Alaska, following the <i>Exxon Valdez</i> oil spill. The spill resulted in the removal of a large number of sea otters in 1989, and as of 1998, the portion of the population in the heavily oiled northern Knight Island region had not fully recovered. Between 1996 and 1998, prey consumption rate was higher and the condition of sea otters was better at northern Knight Island than in an unoiled area of the sound (Montague Island). Estimates of prey energy available per unit mass of sea otter were about 4 times higher at Knight than Montague Island, albeit not significantly different between the two areas. Over this same period, the number of sea otters remained constant at northern Knight Island but increased at Montague Island. These data suggest that food was at least as abundant at Knight than at Montague Island, and that recovery of sea otters via intrinsic population growth was limited by factors other than food. However, the availability of food, the prey consumption rate, and the condition of sea otters were all much lower at both Knight and Montague Islands than in areas newly occupied by sea otters where the population growth rate was near the theoretical maximum. It is possible that the relative short supply of food (compared to areas where sea otter population growth rate was high) may have inhibited immigration or interacted with other factors (e.g., oil-induced mortality or predation) to restrict sea otter population growth. Nonetheless, these data suggest that impacts of anthropogenic disturbances on large, often food-limited vertebrate predators can persist in spite of the availability of food resources that are sufficient for intrinsic population growth.

Alaska↗
USGS2002

Sea otter ( Enhydra lutris ) perspective: Part C. Trophic linkages among sea otters and bivalve prey in Prince William Sound, Alaska, in the aftermath of the Exxon Valdez oil spill: Implications for community models in sedimentary habitats

We exploited the Exxon Valdez oil spill in Prince William Sound (PWS), Alaska, to evaluate effects of reduced sea otter densities on prey populations in sedimentary habitats. We considered the need for and characteristics of new models for trophic effects of sea otters on coastal marine benthic communities. We viewed evidence for nonlinear or uncertain patterns of prey response to varying sea otter density as particularly significant for new model structure. We specifically examined responses of densities and size distributions of populations of mussels and clams (several taxonomic and habitat categories), all important sea otter prey in PWS, to reduction in sea otter density caused by the oil spill. We utilized two primary criteria for determining the consistency of prey demographic responses to reduced sea otter densities as predicted by null hypotheses consistent with existing published models. First, prey populations subject to reduced influence by sea otters should be denser and contain proportionately more large individuals than prey populations strongly influenced by sea otter predation. Second, response times of prey demography to reduced otter densities should be similar to response times of prey to increased otter densities, the latter as indicated in existing published models. Results were disparate with regard to expectation for the six categories of prey evaluated. With few exceptions, density data indicated nonconformance with demographic expectations. In contrast, size data for prey indicated conformance with expectation in about half the categories evaluated. We suggest that lingering effects of the oil spill, nonlinear relationships of sea otters and prey that involve thresholds in otter density, uncertainties in prey recruitment patterns, spatial differences in natural disturbance rate, and differences between areas in effects of competing predators are the main factors possibly accounting for patterns in our data. Recruitment and disturbance effects in particular may include significant stochastic components, especially in a temporal context. We suggest that recovered sea otter populations and their prey do not necessarily exist in long-term stable equilibria, and that development of new models incorporating both trophic thresholds and trophic stochasticity will be important in understanding community-level responses to variable sea otter numbers.

Alaska↗
USGS1993

Dynamics and distribution of black abalone populations at San Nicolas Island

Dense populations of black abalones (Haliotis cracherodii Leach) were monitored in permanent intertidal plots at nine sites on San Nicolas Island from 1981 through 1990. Densities were essentially constant at all four sites along the north shore of the island throughout the study period. Densities at five sites along the south shore were more variable, possibly reflecting asynchronous variation in recruitment, mortality resulting from wave disturbance, and removal by people. Temporal variation of abalone densities apparently was not influenced by sea otters or abalone withering syndrome during this study. Abalones were strongly aggregated in space. Highest densities occurred in areas of irregular substrata, apparently as a result of preference for crevices and vertical faces. The locations of dense patches were persistent in time.

California↗
USGS1987

Mortalities of kelp-forest fishes associated with large oceanic waves off central California, 1982-1983

Observations of three incidents of the mass mortality of nearshore fishes are reported; each corresponded to periods of high-amplitude, long-period swells during the 1982-1983 El Niño event along the coast of central California. Members of the nearshore kelp forest fish assemblage, primarily of the genus Sebastes , accounted for 96% of the observed mortalities and S. mystinus (blue rockfish) alone accounted for 72%.

California↗
USGS1986

Status of a translocated sea otter population and its habitat in Washington

During the summers of 1969 and 1970, the Alaska Department of Fish and Game and the Washington Department of Game translocated 59 sea otters from Amchitka Island, Alaska, to release sites in Washington (Jameson et al. 1982, Wildl. Soc. Bull. 10:100-107). Of the 29 released near Pt. Grenvil (Fig. 1) in 1969, 16 are known to have died. In 1970, 30 otters were held in a floating enclosure anchored near James Island, off La Push. They were released nearby in excellent condition on July 1970. Results of surveys from 1977 to 1981 were reported by Jameson et al. (1982). The purpose of this note is to report subsequent additional observations for 1983 and 1985 on the abundance, distribution, and habitat of the sea otter population in Washington

Washington↗
USGS1986

A sublittoral population of Pleurophycus gardneri Setchell and Saunders 1900 (Phaeophyceae: Laminariaceae) in central California

Published distributional records for the stipitate kelp Pleurophycus gardneri Setchell and Saunders 1900 (Phaeophyceae: Laminariaceae) indicae a geographic range from Montague Island (59°58’N, 147°22W), Alaska to Fort Bragg (39°27’N, 123°47’W), California (Druehl 1969, 1970; Kjeldsen 1972). P. gardneri is found primarily in rocky intertidal and shallow subtidal locations (Scagel 1967; Nicholson 1976). In California, populations of P. gardneri have been reported only from the lower rocky intertidal near Fort Bragg (Kjeldsen 1972). On 7 and 8 July 1982 and 23 March 1984 we censused stipitate kelps during SCUBS dives at a site 2.3 km south southeast of Pt. Sierra Nevada (35°41’ N, 121°18’W). we counted kelps in 1 x 5-m plots along a 50-m tape laid across the bottom in an arbitrarily predetermined direction from the skiff anchor. We also measured water depth at 1-m intervals along the tape, using a SCUBA depth gauge. On 20 August 1982, we used the same tehniques to sample kelp densities at a site 2.4 km east southeast of Pt. Piedras Blancas (35°39’N, 121°15’W). The most abundant kelps at the Pt. Sierra Nevada ste were Pterygophora californica Ruprect 1852 (Phaeophyceae: Alariaceae) and a species we tentatively identified as P. gardneri (Table 1). Based on specimens we collected on 8 July 1982, our field identification was subsequently confirmed by I. A. Abbot. Voucher specimens were placed in the Gilbert M. Smith Herbarium at Hopkins Marine Station, Stanford University, Pacific Grove, California.

California↗