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Open Access Publications from the University of California

Scholarly Works (5 results)

  • Article
Scripps Institution of Oceanography Technical Report (1999)

An unexploited population of the sheep crab Loxorhynchus grandis (Majidae, Brachyura) was studied for three years in the nearshore region adjacent to the Scripps Institution of Oceanography. Over 1000 crabs were collected in monthly surveys at three sites in water of between 10 and 20 meters depth. Size, sex, reproductive condition, carapace condition, and leg damage were recorded before crabs were individually tagged and released. Four crab aggregations were observed at one of the sites (Sand Plain). The function of these aggregations seems to be for reproduction, as a lower percentage of brooding females, and a higher percentage of males was observed than when crabs were not aggregated. A total of 564 crabs was tagged at the Pier site and the overall recapture rate was 39%. At the Pier adult females were more abundant than males, were recaptured more often (46% vs. 20%), and were also more sedentary than males. The Jolly-Seber mark-recapture technique was used to estimate the regional L. grandis population size, which ranged between zero and 300 crabs. Juvenile crabs were only found at the Dike Rock site and exhibited a peak in abundance between January and May. Adults were found occasionally at Dike Rock, but were most abundant at the Pier. Peak crab abundance at the Pier was in July for two years, and in January for one year. Adult males had significantly more damage to the claws and first pair of walking legs, and likely lose them in aggressive interactions. Females had a high frequency of damage to the first pair, perhaps sustained in mating behavior, while juveniles had radially symmetric patterns of leg damage, suggesting they were more passive and did not react to threats of leg damage. The speed that these crabs can move (0.40 km hr-1 ) was estimated by following tagged crabs for short periods of time. The results of this study also suggest that L. grandis has both alongshore and offshore separation of ontogenetic stages.

    Cover page: Population dynamics of the sheep crab Loxorhynchus grandis (Majidae) Stimpson 1857 at La Jolla California
    • Article
    • Peer Reviewed
    UC Santa Cruz Previously Published Works (2020)
    Understanding the factors which influence foraging behaviour and success in marine mammals is crucial to predicting how their populations may respond to environmental change. The Australian fur seal (Arctocephalus pusillus doriferus, AUFS) is a predominantly benthic forager on the shallow continental shelf of Bass Strait, and represents the greatest biomass of marine predators in south-eastern Australia. The south-east Australian region is experiencing rapid oceanic warming, predicted to lead to substantial alterations in prey diversity, distribution and abundance. In the present study, foraging effort and indices of foraging success and efficiency were investigated in 138 adult female AUFS (970 foraging trips) during the winters of 1998-2019. Large scale climate conditions had a strong influence on foraging effort, foraging success and efficiency. Foraging effort and foraging success were also strongly influenced by winter chlorophyll-a concentrations and sea-surface height anomalies in Bass Strait. The results suggest increasing foraging effort and decreasing foraging success and efficiency under anticipated environmental conditions, which may have population-level impacts.
      Cover page: Environmental influences on foraging effort, success and efficiency in female Australian fur seals.
      • Article
      • Peer Reviewed
      UC Irvine Previously Published Works (2017)
      Ocean warming, acidification, deoxygenation and reduced productivity are widely considered to be the major stressors to ocean ecosystems induced by emissions of CO2 . However, an overlooked stressor is the change in ocean circulation in response to climate change. Strong changes in the intensity and position of the western boundary currents have already been observed, and the consequences of such changes for ecosystems are beginning to emerge. In this study, we address climatically induced changes in ocean circulation on a global scale but relevant to propagule dispersal for species inhabiting global shelf ecosystems, using a high-resolution global ocean model run under the IPCC RCP 8.5 scenario. The ¼ degree model resolution allows improved regional realism of the ocean circulation beyond that of available CMIP5-class models. We use a Lagrangian approach forced by modelled ocean circulation to simulate the circulation pathways that disperse planktonic life stages. Based on trajectory backtracking, we identify present-day coastal retention, dominant flow and dispersal range for coastal regions at the global scale. Projecting into the future, we identify areas of the strongest projected circulation change and present regional examples with the most significant modifications in their dominant pathways. Climatically induced changes in ocean circulation should be considered as an additional stressor of marine ecosystems in a similar way to ocean warming or acidification.
        • Article
        • Peer Reviewed
        UC Irvine Previously Published Works (2018)
        Climate change is driving a pervasive global redistribution of the planet's species. Species redistribution poses new questions for the study of ecosystems, conservation science and human societies that require a coordinated and integrated approach. Here we review recent progress, key gaps and strategic directions in this nascent research area, emphasising emerging themes in species redistribution biology, the importance of understanding underlying drivers and the need to anticipate novel outcomes of changes in species ranges. We highlight that species redistribution has manifest implications across multiple temporal and spatial scales and from genes to ecosystems. Understanding range shifts from ecological, physiological, genetic and biogeographical perspectives is essential for informing changing paradigms in conservation science and for designing conservation strategies that incorporate changing population connectivity and advance adaptation to climate change. Species redistributions present challenges for human well-being, environmental management and sustainable development. By synthesising recent approaches, theories and tools, our review establishes an interdisciplinary foundation for the development of future research on species redistribution. Specifically, we demonstrate how ecological, conservation and social research on species redistribution can best be achieved by working across disciplinary boundaries to develop and implement solutions to climate change challenges. Future studies should therefore integrate existing and complementary scientific frameworks while incorporating social science and human-centred approaches. Finally, we emphasise that the best science will not be useful unless more scientists engage with managers, policy makers and the public to develop responsible and socially acceptable options for the global challenges arising from species redistributions.
          • Article
          • Peer Reviewed
          UC Irvine Previously Published Works (2017)
          Distributions of Earth's species are changing at accelerating rates, increasingly driven by human-mediated climate change. Such changes are already altering the composition of ecological communities, but beyond conservation of natural systems, how and why does this matter? We review evidence that climate-driven species redistribution at regional to global scales affects ecosystem functioning, human well-being, and the dynamics of climate change itself. Production of natural resources required for food security, patterns of disease transmission, and processes of carbon sequestration are all altered by changes in species distribution. Consideration of these effects of biodiversity redistribution is critical yet lacking in most mitigation and adaptation strategies, including the United Nation's Sustainable Development Goals.
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