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  • 1
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    Scaling laws of marine predator search behaviour (2008)
    Nature Publishing Group (NPG)
    Details
    Publication Date: 2008-02-29
    Description: Many free-ranging predators have to make foraging decisions with little, if any, knowledge of present resource distribution and availability. The optimal search strategy they should use to maximize encounter rates with prey in heterogeneous natural environments remains a largely unresolved issue in ecology. Levy walks are specialized random walks giving rise to fractal movement trajectories that may represent an optimal solution for searching complex landscapes. However, the adaptive significance of this putative strategy in response to natural prey distributions remains untested. Here we analyse over a million movement displacements recorded from animal-attached electronic tags to show that diverse marine predators-sharks, bony fishes, sea turtles and penguins-exhibit Levy-walk-like behaviour close to a theoretical optimum. Prey density distributions also display Levy-like fractal patterns, suggesting response movements by predators to prey distributions. Simulations show that predators have higher encounter rates when adopting Levy-type foraging in natural-like prey fields compared with purely random landscapes. This is consistent with the hypothesis that observed search patterns are adapted to observed statistical patterns of the landscape. This may explain why Levy-like behaviour seems to be widespread among diverse organisms, from microbes to humans, as a 'rule' that evolved in response to patchy resource distributions.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Sims, David W -- Southall, Emily J -- Humphries, Nicolas E -- Hays, Graeme C -- Bradshaw, Corey J A -- Pitchford, Jonathan W -- James, Alex -- Ahmed, Mohammed Z -- Brierley, Andrew S -- Hindell, Mark A -- Morritt, David -- Musyl, Michael K -- Righton, David -- Shepard, Emily L C -- Wearmouth, Victoria J -- Wilson, Rory P -- Witt, Matthew J -- Metcalfe, Julian D -- England -- Nature. 2008 Feb 28;451(7182):1098-102. doi: 10.1038/nature06518.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉Marine Biological Association of the United Kingdom, The Laboratory, Citadel Hill, Plymouth PL1 2PB, UK. dws@mba.ac.uk〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/18305542" target="_blank"〉PubMed〈/a〉
    Keywords: Animals ; *Ecosystem ; Euphausiacea ; *Feeding Behavior ; Fractals ; Gadiformes ; *Marine Biology ; *Models, Biological ; *Motor Activity ; Oceans and Seas ; Population Density ; *Predatory Behavior ; Probability ; Seals, Earless ; Sharks ; Spheniscidae ; Tuna ; Turtles
    Print ISSN: 0028-0836
    Electronic ISSN: 1476-4687
    Topics: Biology , Chemistry and Pharmacology , Medicine , Natural Sciences in General , Physics
    Published by Nature Publishing Group (NPG)
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  • 2
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    Submersible observations on the daytime vertical distribution of Aequorea ?forskalea off the west coast of southern Africa (2005)
    Cambridge University Press
    In:  Journal of the Marine Biological Association of the United Kingdom, 85 (3). pp. 519-522.
    Details
    Publication Date: 2020-07-16
    Description: The vertical distribution of the hydromedusa Aequorea forskalea was investigated using observations from the research submersible 'Jago' collected during 36 dives off the west coast of southern Africa during November 1997 and April 1999. The mean population depth of Aequorea? forskalea deepened with increasing sea surface temperature. We suggest that this behaviour enables individuals to avoid offshore advection, to minimize spatial overlap with other large medusae and to maintain their position over the middle of the shelf.
    Type: Article , PeerReviewed
    Format: text
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  • 3
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    Spatial demography of Calanus finmarchicus in the Irminger Sea (2008)
    Elsevier
    In:  Progress in Oceanography, 76 (1). pp. 39-88.
    Details
    Publication Date: 2015-09-22
    Description: Continuous Plankton Recorder data suggest that the Irminger Sea supports a major proportion of the surface-living population of the copepod Calanus finmarchicus in the northern North Atlantic, but there have been few studies of its population dynamics in the region. In this paper, we document the seasonal changes in the demographic structure of C. finmarchicus in the Irminger Sea from a field programme during 2001/2002, and the associations between its developmental stages and various apparent bio-physical zones. Overwintering stages were found widely at depth (〉500 m) across the Irminger Sea, and surviving females were widely distributed in the surface waters the following spring. However, recruitment of the subsequent generation was concentrated around the fringes of the Irminger Sea basin, along the edges of the Irminger and East Greenland Currents, and not in the central basin. In late summer animals were found descending back to overwintering depths in the Central Irminger Sea. The key factors dictating this pattern of recruitment appear to be (a) the general circulation regime, (b) predation on eggs in the spring, possibly by the surviving G0 stock, and (c) mortality of first feeding naupliar stages in the central basin where food concentrations appear to be low throughout the year. We compared the demographic patterns in 2001/2002 with observations from the only previous major survey in 1963 and with data from the Continuous Plankton Recorder (CPR) surveys. In both previous data sets, the basic structure of G0 ascent from the central basin and G1 recruitment around the fringes was a robust feature, suggesting that it is a recurrent phenomenon. The Irminger Sea is a complex mixing zone between polar and Atlantic water masses, and it has also been identified as a site of sporadic deep convection. The physical oceanographic characteristics of the region are therefore potentially sensitive to climate fluctuations. Despite this, the abundance of C. finmarchicus in the region, as measured by the CPR surveys, appears not to have responded to climate factors linked to the North Atlantic Oscillation Index, in contrast with the stocks in eastern Atlantic areas. We speculate that this may because biological factors (production and mortality), rather than transport processes are the key factors affecting the population dynamics in the Irminger Sea.
    Type: Article , PeerReviewed
    Format: text
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