137 research outputs found
Dive performance in a small-bodied, semi-aquatic mammal in the wild
No full textAquatic foraging is a fundamental component of the behavior of a number of small mammals, yet comprehensive observations of diving are often difficult to obtain under natural circumstances. Semiaquatic mammals, having evolved to exploit prey in both aquatic and terrestrial environments, are generally not as well adapted for diving (or for life in the water) as are fully aquatic species. Because dive ability also tends to increase with body size, small, semiaquatic mammals are presumed to have fairly limited dive ability. Nevertheless, diving plays an important role in food acquisition for many such species. We used time–depth recorders (TDRs) to measure and describe the dive performance of 9 female and 5 male free-living American mink (Neovison vison; body mass approximately 1 kg) on lowland rivers in the southern United Kingdom. We recorded dives up to 2.96 m deep (maximum depth X ¯ 5 1.82 m) and up to 57.9 s in duration (maximum duration X ¯ 5 37.2 s). Dive duration was approximately 40% of that predicted by allometry for all air-breathing diving vertebrates (as might be expected for a small, semiaquatic animal) but was twice as long as previously measured for mink in captivity. Mink performed up to 189 dives per day (X ¯ 5 35.7 dives/day), mostly during daylight, and spent a maximum of 38.4 minutes diving per day (X ¯ 5 7.6 min/day). Some individuals maintained particularly high diving rates over the coldest months, suggesting that the benefits of aquatic foraging in winter outweigh the costs of heat loss. We observed a number of very shallow dives (depth approximately 0.3 m) of particularly long duration (up to 30 s). The function of these dives is currently unknown, but possibilities include searching for prey, travelling, or avoidance of threats. There is only 1 other study of which we are aware that presents detailed measurements of dive performance in a small, shallow-diving, semiaquatic mammal.Fil: Harrington, Lauren. University of Oxford; Reino UnidoFil: Hays, Graeme C.. Swansea University; Reino UnidoFil: Fasola, Laura. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Austral de Investigaciones Científicas; ArgentinaFil: Harrington, Andrew L.. University of Oxford; Reino UnidoFil: Righton, David. No especifíca;Fil: Macdonald, David W.. University of Oxford; Reino Unid
Global Marine Science and Carlsberg: The Golden Connections of Johannes Schmidt (1877-1933)B. PoulsenBrill, Leiden, The Netherlands. ISBN 13: 9789004316362; E-ISBN: 9789004316393 EUR 45:00, USD 54.00, GBP 41.70. Numerous plates and figures. iv, 524 pp.
No full text
All men have need of the cods (sic) (Homer, the Odyssey) or An overview of the results of the EU-CODYSSEY project
No full textNo abstracts are to be cited without prior reference to the author.Cod stocks in European waters are in serious decline, prompting the adoption of Recovery Plans in some areas e.g. North Sea, and similarly serious management measures elsewhere e.g. Barents Sea, Baltic Sea. CODYSSEY (Cod spatial dynamics and vertical movements in European waters and implications for fishery management) is an EU-funded R&D project that involves nine European research institutions in eight different countries. The aim of the project is to improve understanding of the behaviour and distribution of cod in the NE Atlantic in support of stock assessments and Recovery Plans. Over the last four years, members of the CODYSSEY research team have tagged over 2500 cod with electronic tags in four different regions (North Sea, Barents Sea, Baltic Sea and Icelandic plateau). To date, over 450 tags have been returned, yielding tens of thousands of days of data. The results challenge previously held assumptions regarding migratory behaviour, feeding behaviour and the tolerance of cod for extreme environmental conditions. We have been able to derive rates of migration, stock mixing and availability to fisheries from the tag data. The results of the CODYSSEY project are of value to fish biologists and fisheries managers at national and international level
Life in the big blue box: studying the marine life of European eels
No full textNo abstracts are to be cited without prior reference to the author.The European eel (Anguilla Anguilla) is commercially and ecologically important. It has a remarkable catadromous lifecycle: mature adult eels spawn in the sea from which the resulting larvae migrate to the rivers of Europe, grow to partial maturity in freshwater for a period of 5 to 15 years (although sometimes much longer), then return once again to the marine environment to make their second longdistance migration to spawning grounds, where they die after reproduction. So, whilst most of the eel population's growth and production occurs in freshwater, the key life history events of reproduction and recruitment take place in the marine environment. However, despite more than a century of research, much of the ecology, life history and biology of European eels remains a mystery because traditional methods of research have not proved reliable or cost-effective. To solve some of this mystery, the EU has co-funded a large project called that brings together several cutting-edge technologies and research laboratories across Europe
Multi-torsking: simultaneous measurements of cod behaviour show differences between North Sea and Irish Sea stocks
No full textScaling laws of marine predator search behaviour
No full textMany 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. Lévy 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 Lévy-walk-like behaviour close to a theoretical optimum. Prey density distributions also display Lévy-like fractal patterns, suggesting response movements by predators to prey distributions. Simulations show that predators have higher encounter rates when adopting Lévy-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 Lévy-like behaviour seems to be widespread among diverse organisms, from microbes to humans, as a 'rule' that evolved in response to patchy resource distributions.David W. Sims, Emily J. Southall, Nicolas E. Humphries, Graeme C. Hays, Corey J. A. Bradshaw, Jonathan W. Pitchford, Alex James, Mohammed Z. Ahmed, Andrew S. Brierley, Mark A. Hindell, David Morritt, Michael K. Musyl, David Righton, Emily L. C. Shepard, Victoria J. Wearmouth, Rory P. Wilson, Matthew J. Witt & Julian D. Metcalf
Migration of tagged silver eels in the Atlantic 2006-2014
No full textInternational audienceKnown and estimated locations of silver European eels in the Atlantic from 2006 to 2014 derived from popup satellite tags and archival tags. Other data associated with the tagging experiments such as the length, weight, fat percentage, Pankhurst index and Fin index are also included. Locations were either known (from transmitted positions) or were estimated based on the temperature at depth data recorded by electronic tags (latitude) and the timing of steep dives at dawn or dusk (longitude). These data (including detailed methodology) are described within the following publication: Righton et al. (2016). Empirical observations of the spawning migration of European eels: The long and dangerous road to the Sargasso Sea. Science Advances, 2(10), [e1501694]
- …
