56 research outputs found

    Where Snow is a Landmark: Route Direction Elements in Alpine Contexts

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    Route directions research has mostly focused on urban space so far, highlighting human concepts of street networks based on a range of recurring elements such as route segments, decision points, landmarks and actions. We explored the way route directions reflect the features of space and activity in the context of mountaineering. Alpine route directions are only rarely segmented through decision points related to reorientation; instead, segmentation is based on changing topography. Segments are described with various degrees of detail, depending on difficulty. For landmark description, direction givers refer to properties such as type of surface, dimension, colour of landscape features; terrain properties (such as snow) can also serve as landmarks. Action descriptions reflect the geometrical conceptualization of landscape features and dimensionality of space. Further, they are very rich in the semantics of manner of motion

    Trade blocs and trade wars during the interwar period

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    What precisely were the causes and consequences of the trade wars in the 1930s? Were there perhaps deeper forces at work in reorienting global trade prior to the outbreak of World War II? And what lessons may this particular historical episode provide for the present day? To answer these questions, we distinguish between long‐run secular trends in the period from 1920 to 1939 related to the formation of trade blocs and short‐run disruptions associated with the trade wars of the 1930s. We argue that the trade wars mainly served to intensify pre‐existing efforts toward the formation of trade blocs which dated from at least 1920. More speculatively, we argue that the trade wars of the present day may serve a similar purpose as those in the 1930s, that is, the intensification of China‐ and US‐centric trade blocs

    Investigating Behaviour and Population Dynamics of Striped Marlin (Kajikia audax) from the Southwest Pacific Ocean with Satellite Tags

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    Behaviour and distribution of striped marlin within the southwest Pacific Ocean were investigated using electronic tagging data collected from 2005–2008. A continuous-time correlated random-walk Kalman filter was used to integrate double-tagging data exhibiting variable error structures into movement trajectories composed of regular time-steps. This state-space trajectory integration approach improved longitude and latitude error distributions by 38.5 km and 22.2 km respectively. Using these trajectories as inputs, a behavioural classification model was developed to infer when, and where, ‘transiting’ and ‘area-restricted’ (ARB) pseudo-behavioural states occurred. ARB tended to occur at shallower depths (108±49 m) than did transiting behaviours (127±57 m). A 16 day post-release period of diminished ARB activity suggests that patterns of behaviour were affected by the capture and/or tagging events, implying that tagged animals may exhibit atypical behaviour upon release. The striped marlin in this study dove deeper and spent greater time at ≥200 m depth than those in the central and eastern Pacific Ocean. As marlin reached tropical latitudes (20–21°S) they consistently reversed directions, increased swimming speed and shifted to transiting behaviour. Reversals in the tropics also coincided with increases in swimming depth, including increased time ≥250 m. Our research provides enhanced understanding of the behavioural ecology of striped marlin. This has implications for the effectiveness of spatially explicit population models and we demonstrate the need to consider geographic variation when standardizing CPUE by depth, and provide data to inform natural and recreational fishing mortality parameters

    Habitat partitioning and vulnerability of sharks in the Great Barrier Reef Marine Park

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    Sharks present a critical conservation challenge, but little is known about their spatial distribution and vulnerability, particularly in complex seascapes such as Australia's Great Barrier Reef Marine Park (GBRMP). We review (1) the distribution of shark species among the primary habitats of the GBRMP (coral reefs, inshore/shelf, pelagic and deep-water habitats) (2) the relative exploitation of each species by fisheries, and (3) how current catch rates interact with their vulnerability and trophic index. Excluding rays and chimaeras, we identify a total of 82 shark species in the GBRMP. We find that shark research in the GBRMP has yielded little quantitative information on most species. Reef sharks are largely site-fidelic, but can move large distances and some regularly use non-reef habitats. Inshore and shelf sharks use coastal habitats either exclusively or during specific times in their life cycle (e.g. as nurseries). Virtually nothing is known about the distribution and habitat use of the GBRMP's pelagic and deep-water sharks. At least 46 species (53.5 %) are caught in one or more fisheries, but stock assessments are lacking for most. At least 17 of the sharks caught are considered highly vulnerable to exploitation. We argue that users of shark resources should be responsible for demonstrating that a fishery is sustainable before exploitation is allowed to commence or continue. This fundamental change in management principle will safeguard against stock collapses that have characterised many shark fisheries
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