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Arill Engås - One of the best experts on this subject based on the ideXlab platform.
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A comparison between Vessel and trawl tracks as observed by the ITI trawl instrumentation
Fisheries Research, 2000Co-Authors: Arill Engås, Olav Rune Godø, Terje JørgensenAbstract:Instrumentation measuring the tracks of a bottom trawl and a towed underwater vehicle relative to the track of the towing Vessel was tested under varying towing conditions during a research survey in the Barents Sea in 1998. The measured mean distance between Vessel and trawl track (centre of headline) varied from 27 to 213 m during the 15 hauls for which measurements were obtained. The recorded maximum distance between the tracks was 336 m. The deviance appeared to depend on Vessel heading relative to wind and current and on warp length. The magnitude of the measured distance between Vessel and trawl tracks may strongly affect abundance estimates based on data from trawl catches. Depending on the avoidance reactions of different species and length groups to the Approaching Vessel, the track of the trawl relative to that of the Vessel might influence both species and size composition of the catch. Experiments quantifying the relationship between bottom trawl catches and acoustic recordings under the Vessel will be particularly exposed to errors when trawl and Vessel paths diverge. The magnitude of escape responses behind a Vessel during trawling has been reported to vary within limited periods and over-restricted geographical areas. These escape responses have been documented using a towed underwater vehicle without knowing the exact position of the vehicle with regards to Vessel and trawl. Measurements of the positions of the vehicle with regard to the position of the Vessel and trawl during this experiment showed substantial variation both between and within hauls, indicating that at least part of this variability in fish behaviour could be due to the variation in position of the vehicle.
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Reactions of cod (Gadus morhua L.) in the pre-Vessel zone to an Approaching trawler under different light conditions
Hydrobiologia, 1998Co-Authors: Arill Engås, Eli Kyrkjebø Haugland, Jan Tore ØvredalAbstract:The behaviour of cod ( Gadus morhua L.) towards an Approaching Vessel during trawling was studied by means of a stationary positioning system. Three cod were tagged by allowing them to voluntarily swallow transmitters wrapped in bait. The behaviour was recorded before, during and after trawling, which was carried out during high and low light level. Nine hauls were carried out, but only six hauls are included in the analysis, because of technical problems during three hauls. Only in two out of six hauls all three cod were observed. Behaviour towards the Approaching trawler differed from tow to tow. Only three out of thirteen cases were classified as reaction; all three occurred during daylight. In two of the three cases a change in the swimming direction away from the Approaching Vessel was observed, whereas a reduction in swimming speed was recorded in the third case. The reaction distance from the Vessel, between 470 and 1470 m, corresponds to a sound level between 82 and 92 dB re 1 µPa per Hz. There were indications of a lower level of sensory awareness during reduced light level.
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Reactions of cod (Gadus morhua L.) in the pre-Vessel zone to an Approaching trawler under different light conditions
Advances in Invertebrates and Fish Telemetry, 1998Co-Authors: Arill Engås, Eli Kyrkjebø Haugland, Jan Tore ØvredalAbstract:The behaviour of cod (Gadus morhua L.) towards an Approaching Vessel during trawling was studied by means of a stationary positioning system. Three cod were tagged by allowing them to voluntarily swallow transmitters wrapped in bait. The behaviour was recorded before, during and after trawling, which was carried out during high and low light level.
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Reactions of cod (Gadus morhua L.) in the pre-Vessel zone to an Approaching trawler under different light conditions : Preliminary results
Hydrobiologia, 1998Co-Authors: Arill Engås, Eli Kyrkjebø Haugland, Jan Tore ØvredalAbstract:The behaviour of cod (Gadus morhua L.) towards an Approaching Vessel during trawling was studied by means of a stationary positioning system. Three cod were tagged by allowing them to voluntarily swallow transmitters wrapped in bait. The behaviour was recorded before, during and after trawling, which was carried out during high and low light level. Nine hauls were carried out, but only six hauls are included in the analysis, because of technical problems during three hauls. Only in two out of six hauls all three cod were observed. Behaviour towards the Approaching trawler differed from tow to tow. Only three out of thirteen cases were classified as reaction; all three occurred during daylight. In two of the three cases a change in the swimming direction away from the Approaching Vessel was observed, whereas a reduction in swimming speed was recorded in the third case. The reaction distance from the Vessel, between 470 and 1470 m, corresponds to a sound level between 82 and 92 dB re 1 μPa per Hz. There were indications of a lower level of sensory awareness during reduced light level.
Jan Tore Øvredal - One of the best experts on this subject based on the ideXlab platform.
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Reactions of cod (Gadus morhua L.) in the pre-Vessel zone to an Approaching trawler under different light conditions
Hydrobiologia, 1998Co-Authors: Arill Engås, Eli Kyrkjebø Haugland, Jan Tore ØvredalAbstract:The behaviour of cod ( Gadus morhua L.) towards an Approaching Vessel during trawling was studied by means of a stationary positioning system. Three cod were tagged by allowing them to voluntarily swallow transmitters wrapped in bait. The behaviour was recorded before, during and after trawling, which was carried out during high and low light level. Nine hauls were carried out, but only six hauls are included in the analysis, because of technical problems during three hauls. Only in two out of six hauls all three cod were observed. Behaviour towards the Approaching trawler differed from tow to tow. Only three out of thirteen cases were classified as reaction; all three occurred during daylight. In two of the three cases a change in the swimming direction away from the Approaching Vessel was observed, whereas a reduction in swimming speed was recorded in the third case. The reaction distance from the Vessel, between 470 and 1470 m, corresponds to a sound level between 82 and 92 dB re 1 µPa per Hz. There were indications of a lower level of sensory awareness during reduced light level.
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Reactions of cod (Gadus morhua L.) in the pre-Vessel zone to an Approaching trawler under different light conditions
Advances in Invertebrates and Fish Telemetry, 1998Co-Authors: Arill Engås, Eli Kyrkjebø Haugland, Jan Tore ØvredalAbstract:The behaviour of cod (Gadus morhua L.) towards an Approaching Vessel during trawling was studied by means of a stationary positioning system. Three cod were tagged by allowing them to voluntarily swallow transmitters wrapped in bait. The behaviour was recorded before, during and after trawling, which was carried out during high and low light level.
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Reactions of cod (Gadus morhua L.) in the pre-Vessel zone to an Approaching trawler under different light conditions : Preliminary results
Hydrobiologia, 1998Co-Authors: Arill Engås, Eli Kyrkjebø Haugland, Jan Tore ØvredalAbstract:The behaviour of cod (Gadus morhua L.) towards an Approaching Vessel during trawling was studied by means of a stationary positioning system. Three cod were tagged by allowing them to voluntarily swallow transmitters wrapped in bait. The behaviour was recorded before, during and after trawling, which was carried out during high and low light level. Nine hauls were carried out, but only six hauls are included in the analysis, because of technical problems during three hauls. Only in two out of six hauls all three cod were observed. Behaviour towards the Approaching trawler differed from tow to tow. Only three out of thirteen cases were classified as reaction; all three occurred during daylight. In two of the three cases a change in the swimming direction away from the Approaching Vessel was observed, whereas a reduction in swimming speed was recorded in the third case. The reaction distance from the Vessel, between 470 and 1470 m, corresponds to a sound level between 82 and 92 dB re 1 μPa per Hz. There were indications of a lower level of sensory awareness during reduced light level.
Patrick J O Miller - One of the best experts on this subject based on the ideXlab platform.
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sperm whales reduce foraging effort during exposure to 1 2 khz sonar and killer whale sounds
Ecological Applications, 2016Co-Authors: Saana Isojunno, Petter H. Kvadsheim, Charlotte Cure, Peter L Tyack, Paul J Wensveen, Patrick J O MillerAbstract:Abstract . The time and energetic costs of behavioral responses to incidental and experimental sonar exposures, as well as control stimuli, were quantifi ed using hidden state analysis of time series of acoustic and movement data recorded by tags ( DTAG ) attached to 12 sperm whales ( Physeter macrocephalus ) using suction cups. Behavioral state transition modeling showed that tagged whales switched to a non- foraging, non- resting state during both experimental transmissions of low- frequency active sonar from an Approaching Vessel ( LFAS ; 1–2 kH z, source level 214 dB re 1 μPa m, four tag records) and playbacks of potential predator (killer whale, Orcinus orca ) sounds broadcast at naturally occurring sound levels as a positive control from a drifting boat (fi ve tag records). Time spent in foraging states and the probability of prey capture attempts were reduced during these two types of exposures with little change in overall locomotion activity, suggesting an effect on energy intake with no immediate compensation. Whales switched to the active non- foraging state over received sound pressure levels of 131–165 dB re 1 μPa during LFAS exposure. In contrast, no changes in foraging behavior were detected in response to experimental negative controls (no- sonar ship approach or noise control playback) or to experimental medium- frequency active sonar exposures ( MFAS ; 6–7 kH z, source level 199 re 1 μPa m, received sound pressure level [ SPL ] = 73–158 dB re 1 μPa). Similarly, there was no reduction in foraging effort for three whales exposed to incidental, unidentified 4.7–5.1 kH z sonar signals received at lower levels ( SPL = 89–133 dB re 1 μPa). These results demonstrate that similar to predation risk, exposure to sonar can affect functional behaviors, and indicate that increased perception of risk with higher source level or lower frequency may modulate how sperm whales respond to anthropogenic sound.
Eli Kyrkjebø Haugland - One of the best experts on this subject based on the ideXlab platform.
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Reactions of cod (Gadus morhua L.) in the pre-Vessel zone to an Approaching trawler under different light conditions
Hydrobiologia, 1998Co-Authors: Arill Engås, Eli Kyrkjebø Haugland, Jan Tore ØvredalAbstract:The behaviour of cod ( Gadus morhua L.) towards an Approaching Vessel during trawling was studied by means of a stationary positioning system. Three cod were tagged by allowing them to voluntarily swallow transmitters wrapped in bait. The behaviour was recorded before, during and after trawling, which was carried out during high and low light level. Nine hauls were carried out, but only six hauls are included in the analysis, because of technical problems during three hauls. Only in two out of six hauls all three cod were observed. Behaviour towards the Approaching trawler differed from tow to tow. Only three out of thirteen cases were classified as reaction; all three occurred during daylight. In two of the three cases a change in the swimming direction away from the Approaching Vessel was observed, whereas a reduction in swimming speed was recorded in the third case. The reaction distance from the Vessel, between 470 and 1470 m, corresponds to a sound level between 82 and 92 dB re 1 µPa per Hz. There were indications of a lower level of sensory awareness during reduced light level.
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Reactions of cod (Gadus morhua L.) in the pre-Vessel zone to an Approaching trawler under different light conditions
Advances in Invertebrates and Fish Telemetry, 1998Co-Authors: Arill Engås, Eli Kyrkjebø Haugland, Jan Tore ØvredalAbstract:The behaviour of cod (Gadus morhua L.) towards an Approaching Vessel during trawling was studied by means of a stationary positioning system. Three cod were tagged by allowing them to voluntarily swallow transmitters wrapped in bait. The behaviour was recorded before, during and after trawling, which was carried out during high and low light level.
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Reactions of cod (Gadus morhua L.) in the pre-Vessel zone to an Approaching trawler under different light conditions : Preliminary results
Hydrobiologia, 1998Co-Authors: Arill Engås, Eli Kyrkjebø Haugland, Jan Tore ØvredalAbstract:The behaviour of cod (Gadus morhua L.) towards an Approaching Vessel during trawling was studied by means of a stationary positioning system. Three cod were tagged by allowing them to voluntarily swallow transmitters wrapped in bait. The behaviour was recorded before, during and after trawling, which was carried out during high and low light level. Nine hauls were carried out, but only six hauls are included in the analysis, because of technical problems during three hauls. Only in two out of six hauls all three cod were observed. Behaviour towards the Approaching trawler differed from tow to tow. Only three out of thirteen cases were classified as reaction; all three occurred during daylight. In two of the three cases a change in the swimming direction away from the Approaching Vessel was observed, whereas a reduction in swimming speed was recorded in the third case. The reaction distance from the Vessel, between 470 and 1470 m, corresponds to a sound level between 82 and 92 dB re 1 μPa per Hz. There were indications of a lower level of sensory awareness during reduced light level.
Saana Isojunno - One of the best experts on this subject based on the ideXlab platform.
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sperm whales reduce foraging effort during exposure to 1 2 khz sonar and killer whale sounds
Ecological Applications, 2016Co-Authors: Saana Isojunno, Petter H. Kvadsheim, Charlotte Cure, Peter L Tyack, Paul J Wensveen, Patrick J O MillerAbstract:Abstract . The time and energetic costs of behavioral responses to incidental and experimental sonar exposures, as well as control stimuli, were quantifi ed using hidden state analysis of time series of acoustic and movement data recorded by tags ( DTAG ) attached to 12 sperm whales ( Physeter macrocephalus ) using suction cups. Behavioral state transition modeling showed that tagged whales switched to a non- foraging, non- resting state during both experimental transmissions of low- frequency active sonar from an Approaching Vessel ( LFAS ; 1–2 kH z, source level 214 dB re 1 μPa m, four tag records) and playbacks of potential predator (killer whale, Orcinus orca ) sounds broadcast at naturally occurring sound levels as a positive control from a drifting boat (fi ve tag records). Time spent in foraging states and the probability of prey capture attempts were reduced during these two types of exposures with little change in overall locomotion activity, suggesting an effect on energy intake with no immediate compensation. Whales switched to the active non- foraging state over received sound pressure levels of 131–165 dB re 1 μPa during LFAS exposure. In contrast, no changes in foraging behavior were detected in response to experimental negative controls (no- sonar ship approach or noise control playback) or to experimental medium- frequency active sonar exposures ( MFAS ; 6–7 kH z, source level 199 re 1 μPa m, received sound pressure level [ SPL ] = 73–158 dB re 1 μPa). Similarly, there was no reduction in foraging effort for three whales exposed to incidental, unidentified 4.7–5.1 kH z sonar signals received at lower levels ( SPL = 89–133 dB re 1 μPa). These results demonstrate that similar to predation risk, exposure to sonar can affect functional behaviors, and indicate that increased perception of risk with higher source level or lower frequency may modulate how sperm whales respond to anthropogenic sound.