Glenn R. VanBlaricom

The community ecology of sea otters

This book discusses effects of predation by sea otters in nearshore benthic communities of the North Pacific. It includes chapters written by researchers in kelp forest, rocky intertidal, and soft sediment habitats. They review current knowledge and areas of controversy, present new data, and identify needs for additional study. In the concluding chapters areas of consensus as well as barriers to overgeneralization and accurate prediction are noted. This is the first technical book focusing on empirical studies of effects of a marine mammal on marine ecosystems. Researchers, fisheries and environmental conservation organizations will find this book a valuable study.

Geographic variation of persistent organic pollutant levels in humpback whale (Megaptera novaeangliae) feeding areas of the North Pacific and North Atlantic

Seasonal feeding behavior and high fidelity to feeding areas allow humpback whales (Megaptera novaeangliae) to be used as biological indicators of regional contamination. Biopsy blubber samples from male individuals (n = 67) were collected through SPLASH, a multinational research project, in eight North Pacific feeding grounds. Additional male samples (n = 20) were collected from one North Atlantic feeding ground. Persistent organic pollutants were measured in the samples and used to assess contaminant distribution in the study areas. North Atlantic (Gulf of Maine) whales were more contaminated than North Pacific whales, showing the highest levels of polychlorinated biphenyls (PCBs), polybrominated diphenyl ethers (PBDEs), and chlordanes. The highest dichlorodiphenyltrichloroethane (DDT) levels were detected in whales feeding off southern California, USA. High-latitude regions were characterized by elevated levels of hexachlorocyclohexanes (HCHs) but generally nondetectable concentrations of PBDEs. Age was shown to have a positive relationship with SigmaPCBs, SigmaDDTs, Sigmachlordanes, and total percent lipid. Contaminant levels in humpback whales were comparable to other mysticetes and lower than those found in odontocete cetaceans and pinnipeds. Although these concentrations likely do not represent a significant conservation threat, levels in the Gulf of Maine and southern California may warrant further study.

Implications of three viability models for the conservation status of the western population of Steller sea lions (Eumetopias jubatus)

Two distinct viability models are developed for Steller sea lions (Eumetopias jubatus) to evaluate the sensitivity of extinction risk to various levels of stochasticity, spatial scale and density dependence. These models include a metapopulation model, Analysis of the Likelihood of Extinction (ALEX; Possingham et al., 1992; Possingham, H., Davies, I.A., Noble, I. 1992. ALEX 2.2 Operation Manual. Department of Applied Mathematics, University of Adelaide, Adelaide, SA 5005; Australia.), and a model that incorporates both sampling and process error in estimating population parameters from timeseries data (Gerber and DeMaster, 1999; Gerber, L.R., DeMaster, D.P. 1999. An approach to endangered species act classification of long-lived vertebrates: a case study of north Pacific humpback whales. Conservation Biology 13 (5);1203–1214.). Results are compared with a third model that encompasses three different geographic scales (York et al., 1996; York, A.E., Merrick, R.L., Loughlin, T.R. 1996. An analysis of the Steller Sea lion metapopulation in Alaska. In: McCullough, D.R. (Ed.), Metapopulations and Wildlife Conservation. Island Press, Covelo, CA pp. 259–292). The combination of modeling approaches provides a basis for considering how model parameterization and the selection of classification criteria affect both model results and potential status determinations. Results from the models generally agree with regard to central tendency, 25th and 75th percentile times to extinction. For Steller sea lions, the distributions of time to extinction for each model were narrower than the range of extinction distributions between models. If this finding applies generally to listed species, it would suggest that more than one viability model should be considered when listing decisions are made. On a more applied basis, the results of our analysis provide a quantitative assessment of extinction risk of Steller sea lions in the context of its status pursuant to the US Endangered Species Act. # 2001 Elsevier Science Ltd. All rights reserved.

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.

Leaner leviathans: body condition variation in a critically endangered whale population

Abstract The role of environmental limitation and density-dependent regulation in shaping populations is debated in ecology. Populations at low densities may offer an unobstructed view of basic environmental and physiological interactions that impact individual fitness and thus population productivity. The energy reserves of an organism are reflected in its body condition, a measure linking individual fitness and the environment. From 1997 to 2007, we monitored the critically endangered western gray whale (Eschrichtius robustus) population on its primary summer feeding ground off the northeastern coast of Sakhalin Island, Russia. This effort resulted in a large data set of photo-identification images from 5,007 sightings of 168 individual whales that we used to visually assess western gray whale body condition. We quantified temporal variation in the resulting 1,539 monthly body condition determinations with respect to observations of reproductive status and sex. Western gray whale body condition varied annually, and we identified years of significantly better (2004) and worse (1999, 2006, and 2007) body condition. This study is the 1st to track the within-season body condition of individual whales. Body condition improved significantly as the summer progressed, although results suggest that not all whales replenish their energy stores by the end of the season. The body condition of lactating females was significantly worse than that of other whales at all times and was most often determined to be compromised. The body condition of their weaning calves exhibited no temporal variation and was consistently good. It is possible lactating females provide an energetic buffer to their offspring at the expense of their own body condition and future reproductive success. Findings from the analysis establish a foundation for quantifying links between western gray whale body condition, demographic parameters, and environmental conditions; and provide a baseline for monitoring individual and population condition of an ecosystem sentinel species in a changing environment. Overall, this study highlights the presence of density-independent environmental and physiological mechanisms that affect the abundance and growth of populations.

OVERALL STATUS AND THREATS ASSESSMENT OF BLACK ABALONE (HALIOTIS CRACHERODII LEACH, 1814) POPULATIONS IN CALIFORNIA

ABSTRACT The black abalone (Haliotis cracherodii Leach, 1814) is a relatively large prosobranch gastropod mollusc ranging from approximately Point Arena in northern California to Bahia Tortugas and Isla Guadalupe, Mexico. In the United States, populations of black abalone on offshore islands, especially those of southern California, were particularly large prior to the mid 1980s. Analysis of long-term fishery-dependent and -independent data revealed that fishing pressure in combination with a lethal disease, withering syndrome, has resulted in mass mortalities of 95% or greater in black abalone populations south of Monterey County, CA. Reduction in local densities below the threshold necessary for successful fertilization (0.34/m2) has been a widespread and pervasive consequence of population reductions by withering syndrome and other factors. The most significant current and future threat that the black abalone faces is that imposed by the spread of withering syndrome, known to be enhanced by periods of ocean warming. Other factors, such as illegal take, ocean pollution, and natural predation, also pose risks to remaining populations and those that may be restored via active management in the future. Without identification, development, and implementation of effective measures to counter the population-level effects of withering syndrome, remaining black abalone populations may experience further declines.

Predictive modelling of habitat selection 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.

EFFECTS OF VESSEL ACTIVITY ON THE NEAR-SHORE ECOLOGY OF KITTLITZ'S MURRELETS (BRACHYRAMPHUS BREVIROSTRIS) IN GLACIER BAY, ALASKA

Abstract Summer breeding populations of Kittlitzs Murrelets (Brachyramphus brevirostris) have declined by 80–90% in southeastern Alaska during the past 25 years. Boating activities overlap considerably in space and time with Kittlitzs Murrelets in Glacier Bay, and disturbance could affect individuals by causing them to fly away from preferred foraging sites, thereby disrupting foraging bouts or resting periods. We observed the effects of vessel activity on Kittlitzs Murrelets at sea for each of three response variables (density, group size, and behaviors) in Glacier Bay. Response variables were characterized at three time-scales of inference: immediate (instantaneous response to vessel passage), short-term (response that persisted 30 min after vessel passage), and daily (response on days with different vessel traffic rates). Group size was not affected by vessel activity. By contrast, near-shore densities were suppressed temporarily by vessel passage but recovered within the day. Density effects did not persist at the daily time-scale and, therefore, did not result in persistent loss of foraging habitat for Kittlitzs Murrelets. Also, behavior was affected at both the immediate and daily time-scales, but not at the short-term time-scale, and may have affected Kittlitzs Murrelets by increasing the amount of time spent flying, which is energetically costly. Vessel passage caused a 30-fold increase in flight behavior (from 0% to 30%). Large and fast-moving vessels caused the greatest disturbance to Kittlitzs Murrelets, which has implications for management of vessel activity.

Testing the generality of the trophic cascade paradigm for sea otters: a case study with kelp forests in northern Washington, USA

Trophic cascade hypotheses for biological communities, linking predation by upper trophic levels to major features of ecological structure and dynamics at lower trophic levels, are widely subscribed and may influence conservation policy. Few such hypotheses have been evaluated for temporal or spatial generality. Previous studies of sea otter (Enhydra lutris) predation along the outer coast of North America suggest a pattern, often elevated to the status of paradigm, in which sea otter presence leads to reduced sea urchin (Strongylocentrotus spp.) biomass and rapid increases in abundance and diversity of annual algal species, followed by a decline in diversity as one or a few perennial algal species become dominant. Both sea otter predation and commercial sea urchin harvest are ecologically and economically important sources of urchin mortality in nearshore benthic systems in northern Washington marine waters. We recorded changes in density of macroalgae in San Juan Channel, a marine reserve in the physically protected inland waters of northern Washington, resulting from three levels of experimental urchin harvest: (1) simulated sea otter predation (monthly complete harvest of sea urchins), (2) simulated commercial urchin harvest (annual size-selective harvest of sea urchins), and (3) no harvest (control). The two experimental urchin removal treatments did not significantly increase the density of perennial (Agarum and Laminaria) or annual (Desmarestia, Costaria, Alaria and Nereocystis) species of macroalgae after 2 years, despite significant and persistent decreases in urchin densities. Our results suggest that other factors such as grazing by other invertebrates, the presence of dense Agarum stands, and recruitment frequency of macroalgae and macroinvertebrates may play a large role in influencing community structure in San Juan Channel and other physically protected marine waters within the range of sea otters.

Regional differences in the spatial and temporal heterogeneity of oceanographic habitat used by Steller sea lions.

Over the past three decades, the decline and altered spatial distribution of the western stock of Steller sea lions (Eumetopias jubatus) in Alaska have been attributed to changes in the distribution or abundance of their prey due to the cumulative effects of fisheries and environmental perturbations. During this period, dietary prey occurrence and diet diversity were related to population decline within metapopulation regions of the western stock of Steller sea lions, suggesting that environmental conditions may be variable among regions. The objective of this study, therefore, was to examine regional differences in the spatial and temporal heterogeneity of oceanographic habitat used by Steller sea lions within the context of recent measures of diet diversity and population trajectories. Habitat use was assessed by deploying satellite-depth recorders and satellite relay data loggers on juvenile Steller sea lions (n = 45) over a five-year period (2000-2004) within four regions of the western stock, including the western, central, and eastern Aleutian Islands, and central Gulf of Alaska. Areas used by sea lions during summer months (June, July, and August) were demarcated using satellite telemetry data and characterized by environmental variables (sea surface temperature [SST] and chlorophyll a [chl a]), which possibly serve as proxies for environmental processes or prey. Spatial patterns of SST diversity and Steller sea lion population trends among regions were fairly consistent with trends reported for diet studies, possibly indicating a link between environmental diversity, prey diversity, and distribution or abundance of Steller sea lions. Overall, maximum spatial heterogeneity coupled with minimal temporal variability of SST appeared to be beneficial for Steller sea lions. In contrast, these patterns were not consistent for chl a, and there appeared to be an ecological threshold. Understanding how Steller sea lions respond to measures of environmental heterogeneity will ultimately be useful for implementing ecosystem management approaches and developing additional conservation strategies.