Browsing by Author "Kato, Akiko"
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- Data packageData from: At-sea distribution and prey selection of Antarctic petrels and commercial krill fisheries(2016-10-10) Descamps, Sébastien; Tarroux, Arnaud; Cherel, Yves; Delord, Karine; Godø, Olaf R.; Kato, Akiko; Krafft, Bjørn A.; Lorentsen, Svein-Håkon; Ropert-Coudert, Yan; Skaret, Georg; Varpe, ØysteinCommercial fisheries may impact marine ecosystems and affect populations of predators like seabirds. In the Southern Ocean, there is an extensive fishery for Antarctic krill Euphausia superba that is projected to increase further. Comparing distribution and prey selection of fishing operations versus predators is needed to predict fishery-related impacts on krill-dependent predators. In this context, it is important to consider not only predators breeding near the fishing grounds but also the ones breeding far away and that disperse during the non-breeding season where they may interact with fisheries. In this study, we first quantified the overlap between the distribution of the Antarctic krill fisheries and the distribution of a krill dependent seabird, the Antarctic petrel Thalassoica antarctica, during both the breeding and non-breeding season. We tracked birds from the world biggest Antarctic petrel colony (Svarthamaren, Dronning Maud Land), located >1000 km from the main fishing areas, during three consecutive seasons. The overall spatial overlap between krill fisheries and Antarctic petrels was limited but varied greatly among and within years, and was high in some periods during the non-breeding season. In a second step, we described the length frequency distribution of Antarctic krill consumed by Antarctic petrels, and compared this with results from fisheries, as well as from diet studies in other krill predators. Krill taken by Antarctic petrels did not differ in size from that taken by trawls or from krill taken by most Antarctic krill predators. Selectivity for specific Antarctic krill stages seems generally low in Antarctic predators. Overall, our results show that competition between Antarctic petrels and krill fisheries is currently likely negligible. However, if krill fisheries are to increase in the future, competition with the Antarctic petrel may occur, even with birds breeding thousands of kilometers away.
- Data packageData from: Flexible flight response to challenging wind conditions in a commuting Antarctic seabird: do you catch the drift?(2016-01-14) Tarroux, Arnaud; Weimerskirch, Henri; Wang, Sheng-Hung; Bromwich, David H.; Cherel, Yves; Kato, Akiko; Ropert-Coudert, Yan; Varpe, Øystein; Yoccoz, Nigel G.; Descamps, SébastienFlight is intrinsically an energetically costly way of moving and birds have developed morphological, physiological and behavioural adaptations to minimize these costs. Central-place foraging seabirds commute regularly between nesting and foraging areas, providing us with opportunities to investigate their behavioural response to environmental conditions that may affect flight, such as wind. Here we tested hypotheses on how wind conditions influence flight behaviour in situations devoid of the confounding effect that, for instance, active foraging behaviour can have on movement patterns. We studied the Antarctic petrel, Thalassoica antarctica, a seabird breeding far inland in Antarctica and commuting through vast ice-covered areas characterized by steady and strong winds as well as a strict absence of foraging opportunities. We combined the three-dimensional location data from 79 GPS tracks with atmospheric wind data over three consecutive breeding seasons (2011-2013) in order to assess individual flight responses to wind conditions. Antarctic petrels encountered generally unfavourable winds, particularly during return flights. Despite their capacity to adjust their speed and heading in order to maintain constant track direction (compensation) in the strongest winds, they generally drifted as wind strengthened. Strong winds induced low-altitude flight. Birds tended to otherwise fly relatively high, but at altitudes with more favourable winds than what they would have encountered if flying higher. Our results show that commuting Antarctic petrels: (1) can tolerate a certain amount of drift according to wind conditions and (2) might be more limited by their ability to assess drift, rather than compensate for it, at least during returning flights.