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Ian B Todd - One of the best experts on this subject based on the ideXlab platform.
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diel echolocation activity of harbour porpoises Phocoena Phocoena around north sea offshore gas installations
Ices Journal of Marine Science, 2009Co-Authors: Victoria L G Todd, William D Pearse, Nick C Tregenza, Paul A Lepper, Ian B ToddAbstract:Todd, V. L. G., Pearse, W. D., Tregenza, N. C., Lepper, P. A., and Todd, I. B. 2009. Diel echolocation activity of harbour porpoises (Phocoena Phocoena) around North Sea offshore gas installations. - ICES Journal of Marine Science, 66: 734-745.Echolocation clicks of harbour porpoises (Phocoena Phocoena) were detected with T-PODs, autonomous, passive, acoustic-monitoring devices, deployed from an offshore-exploration-drilling-rig and gas-production-platform complex in the Dogger Bank region of the North Sea from 2005 to 2006. Echolocation-click trains were categorized into four phases of the diel cycle: morning, day, evening, and night. Porpoises were present near (<200 m) the platform, and there was a pronounced diel pattern in echolocation activity; the number of porpoise encounters (visits) was greater by night than by day. The number of click trains with a minimum inter-click interval of <10 ms also increased at night. This was confirmed by a comparison of the ratios of feeding buzzes to search-phase clicks (feeding buzz ratios) and an analysis of the changes in pulse-repetition frequencies within each train. A reasonable interpretation of this pattern was that porpoises were feeding below or around the platform at night. The evidence for changes in activity during the morning and evening was less clear, so these may be transitional phases. The pattern of porpoise-echolocation behaviour around this platform is related most probably to the diel activity of their prey. If porpoises cluster regularly around such installations within 500-m shipping exclusion zones, they may be omitted from population surveys. We conclude that offshore installations may play an important role as nocturnal porpoise-feeding stations in an overfished environment, but that further replicated and controlled studies are required. These findings should be taken into consideration during offshore-installation-decommissioning decisions in the North Sea.
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Diel echolocation activity of harbour porpoises (Phocoena Phocoena) around North Sea offshore gas installations
ICES Journal of Marine Science, 2009Co-Authors: Victoria L G Todd, William D Pearse, Nick C Tregenza, Paul A Lepper, Ian B ToddAbstract:Todd, V. L. G., Pearse, W. D., Tregenza, N. C., Lepper, P. A., and Todd, I. B. 2009. Diel echolocation activity of harbour porpoises (Phocoena Phocoena) around North Sea offshore gas installations. - ICES Journal of Marine Science, 66: 734-745.Echolocation clicks of harbour porpoises (Phocoena Phocoena) were detected with T-PODs, autonomous, passive, acoustic-monitoring devices, deployed from an offshore-exploration-drilling-rig and gas-production-platform complex in the Dogger Bank region of the North Sea from 2005 to 2006. Echolocation-click trains were categorized into four phases of the diel cycle: morning, day, evening, and night. Porpoises were present near (
Victoria L G Todd - One of the best experts on this subject based on the ideXlab platform.
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diel echolocation activity of harbour porpoises Phocoena Phocoena around north sea offshore gas installations
Ices Journal of Marine Science, 2009Co-Authors: Victoria L G Todd, William D Pearse, Nick C Tregenza, Paul A Lepper, Ian B ToddAbstract:Todd, V. L. G., Pearse, W. D., Tregenza, N. C., Lepper, P. A., and Todd, I. B. 2009. Diel echolocation activity of harbour porpoises (Phocoena Phocoena) around North Sea offshore gas installations. - ICES Journal of Marine Science, 66: 734-745.Echolocation clicks of harbour porpoises (Phocoena Phocoena) were detected with T-PODs, autonomous, passive, acoustic-monitoring devices, deployed from an offshore-exploration-drilling-rig and gas-production-platform complex in the Dogger Bank region of the North Sea from 2005 to 2006. Echolocation-click trains were categorized into four phases of the diel cycle: morning, day, evening, and night. Porpoises were present near (<200 m) the platform, and there was a pronounced diel pattern in echolocation activity; the number of porpoise encounters (visits) was greater by night than by day. The number of click trains with a minimum inter-click interval of <10 ms also increased at night. This was confirmed by a comparison of the ratios of feeding buzzes to search-phase clicks (feeding buzz ratios) and an analysis of the changes in pulse-repetition frequencies within each train. A reasonable interpretation of this pattern was that porpoises were feeding below or around the platform at night. The evidence for changes in activity during the morning and evening was less clear, so these may be transitional phases. The pattern of porpoise-echolocation behaviour around this platform is related most probably to the diel activity of their prey. If porpoises cluster regularly around such installations within 500-m shipping exclusion zones, they may be omitted from population surveys. We conclude that offshore installations may play an important role as nocturnal porpoise-feeding stations in an overfished environment, but that further replicated and controlled studies are required. These findings should be taken into consideration during offshore-installation-decommissioning decisions in the North Sea.
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Diel echolocation activity of harbour porpoises (Phocoena Phocoena) around North Sea offshore gas installations
ICES Journal of Marine Science, 2009Co-Authors: Victoria L G Todd, William D Pearse, Nick C Tregenza, Paul A Lepper, Ian B ToddAbstract:Todd, V. L. G., Pearse, W. D., Tregenza, N. C., Lepper, P. A., and Todd, I. B. 2009. Diel echolocation activity of harbour porpoises (Phocoena Phocoena) around North Sea offshore gas installations. - ICES Journal of Marine Science, 66: 734-745.Echolocation clicks of harbour porpoises (Phocoena Phocoena) were detected with T-PODs, autonomous, passive, acoustic-monitoring devices, deployed from an offshore-exploration-drilling-rig and gas-production-platform complex in the Dogger Bank region of the North Sea from 2005 to 2006. Echolocation-click trains were categorized into four phases of the diel cycle: morning, day, evening, and night. Porpoises were present near (
Anders Galatius - One of the best experts on this subject based on the ideXlab platform.
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Geographic variation of skeletal ontogeny and skull shape in the harbour porpoise (Phocoena Phocoena)
Canadian Journal of Zoology, 2011Co-Authors: Anders Galatius, Pavel Gol'dinAbstract:All extant porpoise species show paedomorphic skeletal traits. These traits are hypothesized to be connected with rapid growth to reproductive size and could thus show geographic variation according to ecological circumstances. To inves- tigate this, skeletal ontogeny was compared among harbour porpoises from California, West Greenland, the inner Danish waters, and the Sea of Azov. Porpoises from California grew to larger sizes than Danish porpoises, which were again larger than Greenlandic porpoises, whereas Azov porpoises were smallest. Size differences were largely attributable to differences in timing of offset of growth. Expression of paedomorphosis followed the same pattern among populations and sexes as adult sizes; Californian porpoises were less paedomorphic than the other populations across all assessed traits, whereas por- poises from Azov were the most paedomorphic. We propose that the larger size and less profound paedomorphism seen in Californian porpoises are attributable to fluctuation of prey availability, owing to variation in upwelling on which productiv- ity in Californian waters depends. Skull shapes after correction for allometry were significantly different among all popula- tions, Sea of Azov porpoises being most divergent. There was no overlap of skull shapes between the Atlantic, the Pacific, and Azov, supporting the current division of harbor porpoises (Phocoena Phocoena (L., 1758)) into three subspecies (Pho- coena Phocoena Phocoena (L., 1758), Phocoena Phocoena relicta Abel, 1905, and Phocoena Phocoena vomerina Gill, 1865).
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Interspecific variation of ontogeny and skull shape among porpoises (Phocoenidae).
Journal of Morphology, 2010Co-Authors: Anders Galatius, Marie Schou Frandsen, Annalisa Berta, R. Natalie P. GoodallAbstract:All extant members of Phocoenidae (por- poises) have been characterized as pedomorphic based on skeletal characters. To investigate the ontogenetic background for pedomorphosis and assess interspecific differences in ontogeny among phocoenids, samples of the six extant species were compared in terms of devel- opment of both epiphyseal and cranial suture fusion. Across all species, full maturity of the vertebral column was rare. Vertebral epiphyseal development did not pro- gress so far in most Phocoena Phocoena as in Phocoe- noides dalli and Phocoena dioptrica. P. Phocoena, Phocoena spinipinnis, Ph. dalli, and P. dioptrica, for which large series were available, were further compared in terms of ontogeny of cranial shape by three-dimen- sional geometric morphometrics. Ph. dalli and P. diop- trica generally showed further development of cranial sutures than the other species. Postnatal skull shape de- velopment was similar for all species studied; the major- ity of interspecific shape differences are present at partu- rition. Smaller species had a higher rate of shape develop- ment relative to growth in size than Ph. dalli and P. dioptrica, but they still showed less allometric develop- ment due to less postnatal growth. Interspecific shape dif- ferences indicate phylogenetic relationships similar to that proposed based on morphology or convergent evolu- tion of the two pelagic species, Ph. dalli and P. dioptrica, under the scenarios suggested by recent molecular stud- ies. A shape trend coinciding with habitat preference was detected; in species with pelagic preference the position and orientation of the foramen magnum aligned the skull with the vertebral column; the rostrum showed less ven- tral inclination, and the facial region was larger and more concave in lateral aspect. J. Morphol. 272:136-148, 2011. 2010 Wiley-Liss, Inc.
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Sexually dimorphic proportions of the harbour porpoise (Phocoena Phocoena) skeleton.
Journal of anatomy, 2005Co-Authors: Anders GalatiusAbstract:Sexual differences in growth, allometric growth patterns and skeletal proportions were investigated by linear measurements of skeletal parts on 225 harbour porpoises (Phocoena Phocoena) from the inner Danish and adjacent waters. Females show larger asymptotic sizes and extended period of growth compared with males. Measurements of the skull and flipper bones show negative allometry, whereas those of the bones of the body generally show positive allometry. There are no statistically significant intersexual differences in allometry except for the pelvic bones, where the males show stronger positive allometry. Throughout the range of individual sizes, females have significantly larger skulls and shorter vertebral columns than males for similarly sized individuals. In fully grown specimens, the condylobasal length of females makes up a smaller proportion of total length, and the vertebrae make up a larger proportion as compared with males. As these characters show negative and positive allometry, respectively, it is suggested that males finish their development at an earlier stage than females, retaining more paedomorphic proportions of the skeleton. Paedomorphosis in fully grown males relative to females is also found in the vertebral epiphyses that mature later in males than females, although the males finish growth at a younger age.
William D Pearse - One of the best experts on this subject based on the ideXlab platform.
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diel echolocation activity of harbour porpoises Phocoena Phocoena around north sea offshore gas installations
Ices Journal of Marine Science, 2009Co-Authors: Victoria L G Todd, William D Pearse, Nick C Tregenza, Paul A Lepper, Ian B ToddAbstract:Todd, V. L. G., Pearse, W. D., Tregenza, N. C., Lepper, P. A., and Todd, I. B. 2009. Diel echolocation activity of harbour porpoises (Phocoena Phocoena) around North Sea offshore gas installations. - ICES Journal of Marine Science, 66: 734-745.Echolocation clicks of harbour porpoises (Phocoena Phocoena) were detected with T-PODs, autonomous, passive, acoustic-monitoring devices, deployed from an offshore-exploration-drilling-rig and gas-production-platform complex in the Dogger Bank region of the North Sea from 2005 to 2006. Echolocation-click trains were categorized into four phases of the diel cycle: morning, day, evening, and night. Porpoises were present near (<200 m) the platform, and there was a pronounced diel pattern in echolocation activity; the number of porpoise encounters (visits) was greater by night than by day. The number of click trains with a minimum inter-click interval of <10 ms also increased at night. This was confirmed by a comparison of the ratios of feeding buzzes to search-phase clicks (feeding buzz ratios) and an analysis of the changes in pulse-repetition frequencies within each train. A reasonable interpretation of this pattern was that porpoises were feeding below or around the platform at night. The evidence for changes in activity during the morning and evening was less clear, so these may be transitional phases. The pattern of porpoise-echolocation behaviour around this platform is related most probably to the diel activity of their prey. If porpoises cluster regularly around such installations within 500-m shipping exclusion zones, they may be omitted from population surveys. We conclude that offshore installations may play an important role as nocturnal porpoise-feeding stations in an overfished environment, but that further replicated and controlled studies are required. These findings should be taken into consideration during offshore-installation-decommissioning decisions in the North Sea.
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Diel echolocation activity of harbour porpoises (Phocoena Phocoena) around North Sea offshore gas installations
ICES Journal of Marine Science, 2009Co-Authors: Victoria L G Todd, William D Pearse, Nick C Tregenza, Paul A Lepper, Ian B ToddAbstract:Todd, V. L. G., Pearse, W. D., Tregenza, N. C., Lepper, P. A., and Todd, I. B. 2009. Diel echolocation activity of harbour porpoises (Phocoena Phocoena) around North Sea offshore gas installations. - ICES Journal of Marine Science, 66: 734-745.Echolocation clicks of harbour porpoises (Phocoena Phocoena) were detected with T-PODs, autonomous, passive, acoustic-monitoring devices, deployed from an offshore-exploration-drilling-rig and gas-production-platform complex in the Dogger Bank region of the North Sea from 2005 to 2006. Echolocation-click trains were categorized into four phases of the diel cycle: morning, day, evening, and night. Porpoises were present near (
Nick C Tregenza - One of the best experts on this subject based on the ideXlab platform.
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diel echolocation activity of harbour porpoises Phocoena Phocoena around north sea offshore gas installations
Ices Journal of Marine Science, 2009Co-Authors: Victoria L G Todd, William D Pearse, Nick C Tregenza, Paul A Lepper, Ian B ToddAbstract:Todd, V. L. G., Pearse, W. D., Tregenza, N. C., Lepper, P. A., and Todd, I. B. 2009. Diel echolocation activity of harbour porpoises (Phocoena Phocoena) around North Sea offshore gas installations. - ICES Journal of Marine Science, 66: 734-745.Echolocation clicks of harbour porpoises (Phocoena Phocoena) were detected with T-PODs, autonomous, passive, acoustic-monitoring devices, deployed from an offshore-exploration-drilling-rig and gas-production-platform complex in the Dogger Bank region of the North Sea from 2005 to 2006. Echolocation-click trains were categorized into four phases of the diel cycle: morning, day, evening, and night. Porpoises were present near (<200 m) the platform, and there was a pronounced diel pattern in echolocation activity; the number of porpoise encounters (visits) was greater by night than by day. The number of click trains with a minimum inter-click interval of <10 ms also increased at night. This was confirmed by a comparison of the ratios of feeding buzzes to search-phase clicks (feeding buzz ratios) and an analysis of the changes in pulse-repetition frequencies within each train. A reasonable interpretation of this pattern was that porpoises were feeding below or around the platform at night. The evidence for changes in activity during the morning and evening was less clear, so these may be transitional phases. The pattern of porpoise-echolocation behaviour around this platform is related most probably to the diel activity of their prey. If porpoises cluster regularly around such installations within 500-m shipping exclusion zones, they may be omitted from population surveys. We conclude that offshore installations may play an important role as nocturnal porpoise-feeding stations in an overfished environment, but that further replicated and controlled studies are required. These findings should be taken into consideration during offshore-installation-decommissioning decisions in the North Sea.
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Diel echolocation activity of harbour porpoises (Phocoena Phocoena) around North Sea offshore gas installations
ICES Journal of Marine Science, 2009Co-Authors: Victoria L G Todd, William D Pearse, Nick C Tregenza, Paul A Lepper, Ian B ToddAbstract:Todd, V. L. G., Pearse, W. D., Tregenza, N. C., Lepper, P. A., and Todd, I. B. 2009. Diel echolocation activity of harbour porpoises (Phocoena Phocoena) around North Sea offshore gas installations. - ICES Journal of Marine Science, 66: 734-745.Echolocation clicks of harbour porpoises (Phocoena Phocoena) were detected with T-PODs, autonomous, passive, acoustic-monitoring devices, deployed from an offshore-exploration-drilling-rig and gas-production-platform complex in the Dogger Bank region of the North Sea from 2005 to 2006. Echolocation-click trains were categorized into four phases of the diel cycle: morning, day, evening, and night. Porpoises were present near (