Submarine topography as a predictor of mobile predator hotspots: relevance and applications to conservation planning in the pelagic ocean

Philippe Jean-Francois Bouchet

    Research output: ThesisDoctoral Thesis

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    Abstract

    Many fundamental questions in marine conservation demand adequate knowledge of the spatial dynamics of faunal taxa, individually and collectively. Without robust maps of biota distributions, be they measured or predicted, informed choices about ocean use remain a significant challenge that can reduce the effectiveness of conservation interventions and leave human-wildlife conflicts unresolved. The field of conservation biogeography seeks to forge quantitative theories about global patterns of life and the underlying environmental mechanisms that cause as well as maintain them. This is a useful pursuit on both theoretical and practical grounds; by unravelling drivers of habitat preferences at a range of resolutions, species-specific needs can be better understood, conservation priorities correctly identified and aligned, reserve designs rigorously planned, and management practices optimised. Accordingly, the discipline has recently emerged as a pivotal tool in addressing the Anthropocene-induced biodiversity crisis, with particular relevance in the pelagic biome where our overall grasp of the ecological requirements of many organisms remains several degrees of magnitude coarser than on land.

    In this thesis, I take a hierarchical approach to conservation biogeography in order to assess the role of seabed topography and geomorphology as determinants of pelagic predator hotspots in the eastern Indian Ocean. The prediction of animal occurrence based on landscape and other abiotic variables (termed physical surrogacy) has been pursued as a way to achieve conservation outcomes when detailed biological information is either unavailable or incomplete. It may thus be a pragmatic, though largely unvalidated, framework for identifying critical areas for oceanic fishes and sharks, which are currently amongst of the most data-deficient of extant vertebrates.

    I first explore the concept of terrain complexity and find that the majority of modern geomorphometrics are mathematically redundant, meaning they can be simplified to a small set of independent characteristics that successfully capture different facets of topographic variability. Using these constructs as inputs to statistical models, I then demonstrate that they can prove influential proxies of mobile predator distributions, albeit their performance is not ubiquitously strong. Specifically, in a continental-scale analysis of historical fisheries catches, I reveal that tunas, marlins and mackerels associate closely with submarine canyons throughout parts of a dynamic and heterogeneous ocean basin. Based on regional models of a tropical seascape, I further show that fish and shark assemblages are linked to a lattice of submerged carbonate banks, with species richness rising in proximity to the features' summits. Such examples of (potentially persistent) habitat associations have direct implications for the management of marine megafauna and the design of offshore protected areas, which currently seldom coincide with predator aggregation sites.

    Insofar as documenting and disentangling these associations relies on appropriate data collection tools, I also test a novel visual monitoring technique suitable for use in topographically complex environments typically considered inaccessible for sampling. Trial of the method off the Perth coast (Western Australia) provides initial insights into the likely patterns of animal occupancy around a newly-proclaimed marine reserve, and indicates that a revision of the reserve's boundaries may be warranted to minimise anthropogenic impacts.

    Despite their charisma, economic value and ecological importance, migratory fishes and sharks face increasing threats and could benefit hugely from representative protection both within national waters and on the high seas. I suggest that topography may be harnessed as a blueprint to assist the delineation of priority conservation areas for species previously deemed too mobile to respond to static landscapes.

    Original languageEnglish
    QualificationDoctor of Philosophy
    Publication statusUnpublished - Dec 2015

    Fingerprint

    conservation planning
    topography
    predator
    ocean
    shark
    biogeography
    protected area
    reserve design
    submarine canyon
    animal
    marine park
    ocean basin
    fish
    biome
    habitat selection
    geomorphology
    biota
    hot spot
    management practice
    vertebrate

    Cite this

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    title = "Submarine topography as a predictor of mobile predator hotspots: relevance and applications to conservation planning in the pelagic ocean",
    abstract = "Many fundamental questions in marine conservation demand adequate knowledge of the spatial dynamics of faunal taxa, individually and collectively. Without robust maps of biota distributions, be they measured or predicted, informed choices about ocean use remain a significant challenge that can reduce the effectiveness of conservation interventions and leave human-wildlife conflicts unresolved. The field of conservation biogeography seeks to forge quantitative theories about global patterns of life and the underlying environmental mechanisms that cause as well as maintain them. This is a useful pursuit on both theoretical and practical grounds; by unravelling drivers of habitat preferences at a range of resolutions, species-specific needs can be better understood, conservation priorities correctly identified and aligned, reserve designs rigorously planned, and management practices optimised. Accordingly, the discipline has recently emerged as a pivotal tool in addressing the Anthropocene-induced biodiversity crisis, with particular relevance in the pelagic biome where our overall grasp of the ecological requirements of many organisms remains several degrees of magnitude coarser than on land. In this thesis, I take a hierarchical approach to conservation biogeography in order to assess the role of seabed topography and geomorphology as determinants of pelagic predator hotspots in the eastern Indian Ocean. The prediction of animal occurrence based on landscape and other abiotic variables (termed physical surrogacy) has been pursued as a way to achieve conservation outcomes when detailed biological information is either unavailable or incomplete. It may thus be a pragmatic, though largely unvalidated, framework for identifying critical areas for oceanic fishes and sharks, which are currently amongst of the most data-deficient of extant vertebrates. I first explore the concept of terrain complexity and find that the majority of modern geomorphometrics are mathematically redundant, meaning they can be simplified to a small set of independent characteristics that successfully capture different facets of topographic variability. Using these constructs as inputs to statistical models, I then demonstrate that they can prove influential proxies of mobile predator distributions, albeit their performance is not ubiquitously strong. Specifically, in a continental-scale analysis of historical fisheries catches, I reveal that tunas, marlins and mackerels associate closely with submarine canyons throughout parts of a dynamic and heterogeneous ocean basin. Based on regional models of a tropical seascape, I further show that fish and shark assemblages are linked to a lattice of submerged carbonate banks, with species richness rising in proximity to the features' summits. Such examples of (potentially persistent) habitat associations have direct implications for the management of marine megafauna and the design of offshore protected areas, which currently seldom coincide with predator aggregation sites. Insofar as documenting and disentangling these associations relies on appropriate data collection tools, I also test a novel visual monitoring technique suitable for use in topographically complex environments typically considered inaccessible for sampling. Trial of the method off the Perth coast (Western Australia) provides initial insights into the likely patterns of animal occupancy around a newly-proclaimed marine reserve, and indicates that a revision of the reserve's boundaries may be warranted to minimise anthropogenic impacts. Despite their charisma, economic value and ecological importance, migratory fishes and sharks face increasing threats and could benefit hugely from representative protection both within national waters and on the high seas. I suggest that topography may be harnessed as a blueprint to assist the delineation of priority conservation areas for species previously deemed too mobile to respond to static landscapes.",
    keywords = "Pelagic fishes and sharks, Submarine topography, Biodiversity hotspots, Predictive modelling, Conservation biogeography, Baited stereo-videography, Marine spatial planning, Western Australia",
    author = "Bouchet, {Philippe Jean-Francois}",
    year = "2015",
    month = "12",
    language = "English",

    }

    TY - THES

    T1 - Submarine topography as a predictor of mobile predator hotspots: relevance and applications to conservation planning in the pelagic ocean

    AU - Bouchet, Philippe Jean-Francois

    PY - 2015/12

    Y1 - 2015/12

    N2 - Many fundamental questions in marine conservation demand adequate knowledge of the spatial dynamics of faunal taxa, individually and collectively. Without robust maps of biota distributions, be they measured or predicted, informed choices about ocean use remain a significant challenge that can reduce the effectiveness of conservation interventions and leave human-wildlife conflicts unresolved. The field of conservation biogeography seeks to forge quantitative theories about global patterns of life and the underlying environmental mechanisms that cause as well as maintain them. This is a useful pursuit on both theoretical and practical grounds; by unravelling drivers of habitat preferences at a range of resolutions, species-specific needs can be better understood, conservation priorities correctly identified and aligned, reserve designs rigorously planned, and management practices optimised. Accordingly, the discipline has recently emerged as a pivotal tool in addressing the Anthropocene-induced biodiversity crisis, with particular relevance in the pelagic biome where our overall grasp of the ecological requirements of many organisms remains several degrees of magnitude coarser than on land. In this thesis, I take a hierarchical approach to conservation biogeography in order to assess the role of seabed topography and geomorphology as determinants of pelagic predator hotspots in the eastern Indian Ocean. The prediction of animal occurrence based on landscape and other abiotic variables (termed physical surrogacy) has been pursued as a way to achieve conservation outcomes when detailed biological information is either unavailable or incomplete. It may thus be a pragmatic, though largely unvalidated, framework for identifying critical areas for oceanic fishes and sharks, which are currently amongst of the most data-deficient of extant vertebrates. I first explore the concept of terrain complexity and find that the majority of modern geomorphometrics are mathematically redundant, meaning they can be simplified to a small set of independent characteristics that successfully capture different facets of topographic variability. Using these constructs as inputs to statistical models, I then demonstrate that they can prove influential proxies of mobile predator distributions, albeit their performance is not ubiquitously strong. Specifically, in a continental-scale analysis of historical fisheries catches, I reveal that tunas, marlins and mackerels associate closely with submarine canyons throughout parts of a dynamic and heterogeneous ocean basin. Based on regional models of a tropical seascape, I further show that fish and shark assemblages are linked to a lattice of submerged carbonate banks, with species richness rising in proximity to the features' summits. Such examples of (potentially persistent) habitat associations have direct implications for the management of marine megafauna and the design of offshore protected areas, which currently seldom coincide with predator aggregation sites. Insofar as documenting and disentangling these associations relies on appropriate data collection tools, I also test a novel visual monitoring technique suitable for use in topographically complex environments typically considered inaccessible for sampling. Trial of the method off the Perth coast (Western Australia) provides initial insights into the likely patterns of animal occupancy around a newly-proclaimed marine reserve, and indicates that a revision of the reserve's boundaries may be warranted to minimise anthropogenic impacts. Despite their charisma, economic value and ecological importance, migratory fishes and sharks face increasing threats and could benefit hugely from representative protection both within national waters and on the high seas. I suggest that topography may be harnessed as a blueprint to assist the delineation of priority conservation areas for species previously deemed too mobile to respond to static landscapes.

    AB - Many fundamental questions in marine conservation demand adequate knowledge of the spatial dynamics of faunal taxa, individually and collectively. Without robust maps of biota distributions, be they measured or predicted, informed choices about ocean use remain a significant challenge that can reduce the effectiveness of conservation interventions and leave human-wildlife conflicts unresolved. The field of conservation biogeography seeks to forge quantitative theories about global patterns of life and the underlying environmental mechanisms that cause as well as maintain them. This is a useful pursuit on both theoretical and practical grounds; by unravelling drivers of habitat preferences at a range of resolutions, species-specific needs can be better understood, conservation priorities correctly identified and aligned, reserve designs rigorously planned, and management practices optimised. Accordingly, the discipline has recently emerged as a pivotal tool in addressing the Anthropocene-induced biodiversity crisis, with particular relevance in the pelagic biome where our overall grasp of the ecological requirements of many organisms remains several degrees of magnitude coarser than on land. In this thesis, I take a hierarchical approach to conservation biogeography in order to assess the role of seabed topography and geomorphology as determinants of pelagic predator hotspots in the eastern Indian Ocean. The prediction of animal occurrence based on landscape and other abiotic variables (termed physical surrogacy) has been pursued as a way to achieve conservation outcomes when detailed biological information is either unavailable or incomplete. It may thus be a pragmatic, though largely unvalidated, framework for identifying critical areas for oceanic fishes and sharks, which are currently amongst of the most data-deficient of extant vertebrates. I first explore the concept of terrain complexity and find that the majority of modern geomorphometrics are mathematically redundant, meaning they can be simplified to a small set of independent characteristics that successfully capture different facets of topographic variability. Using these constructs as inputs to statistical models, I then demonstrate that they can prove influential proxies of mobile predator distributions, albeit their performance is not ubiquitously strong. Specifically, in a continental-scale analysis of historical fisheries catches, I reveal that tunas, marlins and mackerels associate closely with submarine canyons throughout parts of a dynamic and heterogeneous ocean basin. Based on regional models of a tropical seascape, I further show that fish and shark assemblages are linked to a lattice of submerged carbonate banks, with species richness rising in proximity to the features' summits. Such examples of (potentially persistent) habitat associations have direct implications for the management of marine megafauna and the design of offshore protected areas, which currently seldom coincide with predator aggregation sites. Insofar as documenting and disentangling these associations relies on appropriate data collection tools, I also test a novel visual monitoring technique suitable for use in topographically complex environments typically considered inaccessible for sampling. Trial of the method off the Perth coast (Western Australia) provides initial insights into the likely patterns of animal occupancy around a newly-proclaimed marine reserve, and indicates that a revision of the reserve's boundaries may be warranted to minimise anthropogenic impacts. Despite their charisma, economic value and ecological importance, migratory fishes and sharks face increasing threats and could benefit hugely from representative protection both within national waters and on the high seas. I suggest that topography may be harnessed as a blueprint to assist the delineation of priority conservation areas for species previously deemed too mobile to respond to static landscapes.

    KW - Pelagic fishes and sharks

    KW - Submarine topography

    KW - Biodiversity hotspots

    KW - Predictive modelling

    KW - Conservation biogeography

    KW - Baited stereo-videography

    KW - Marine spatial planning

    KW - Western Australia

    M3 - Doctoral Thesis

    ER -