Diving behavior of immature, feeding Pacific bluefin tuna (Thunnus thynnus orientalis) in relation to season and area:: the East China Sea and the Kuroshio-Oyashio transition region
Diving behavior of immature, feeding Pacific bluefin tuna (Thunnus thynnus orientalis) in relation to season and area:: the East China Sea and the Kuroshio-Oyashio transition region
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DOI：
10.1111/j.1365-2419.2004.00282.x
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发表时间：
2004-05-01
影响因子：
2.6
通讯作者：
Yamada, H
中科院分区：
文献类型：
--
作者：
Kitagawa, T;Kimura, S;Yamada, H
此前在东中国海对马岛附近释放的太平洋蓝鳍金枪鱼身上发现了24个档案标签。通过分析来自24个标签的压力、环境温度和内部温度的时间序列数据，我们研究了金枪鱼的潜水模式与温跃层深度的关系。在东海，无论是冬季还是夏季，潜水和进食事件几乎全天都在发生，这表明潜水的目的是为了进食。夏季取食频率大于冬季，对应于夏季生长比冬季快。夏季黑潮-漂潮过渡区觅食事件频次远高于东海，但潜水频率较低。平均水平移动距离也明显更高，似乎在这个区域它们可能水平移动以捕食积聚在水面上的猎物。结果表明，除了环境温度结构外，猎物种类的垂直和水平分布对太平洋蓝鳍金枪鱼的摄食行为也起着重要作用。一条蓝鳍金枪鱼迁移到水平和垂直热梯度都更陡峭的溯潮锋面区。这些鱼大部分时间都在温暖的一面度过，白天经常水平游到寒冷的一面，也许是为了觅食。这意味着有一个热障效应，在这种情况下来自于洋潮锋面，对它们的行为有影响。尽管所有受监测的鱼不论季节或地点，每天清晨和黄昏都会潜水，但进食事件的频率很低。这些每天两次的潜水模式可能是对日出和日落时环境光线变化的反应。
Twenty-four archival tags were recovered from Pacific bluefin tuna previously released off Tsushima Island in the East China Sea. By analysis of the time-series data of the pressure and the ambient and internal temperature from the 24 tags, we examined the relationship between the tuna's pattern of diving and the thermocline depth. In the East China Sea, diving and feeding events occurred throughout almost the entire day in both winter and summer, suggesting that the purpose of diving is for feeding. In summer, the feeding frequency was greater than that in winter, which corresponds to the fact that growth is more rapid in summer than in winter. During summer in the Kuroshio-Oyashio transition region, on the other hand, feeding events were much more frequent than those in the East China Sea, in spite of a lower diving frequency. The mean horizontal distance traveled was also significantly higher and it seems that in this area they may move horizontally to feed on prey accumulated at the surface. We conclude that, in addition to the ambient temperature structure, the vertical and horizontal distribution of prey species plays an important role in the feeding behavior of Pacific bluefin tuna. One bluefin tuna migrated to the Oyashio frontal area, where both the horizontal and the vertical thermal gradients are much steeper. The fish spent most of the time on the warmer side of the front and often traveled horizontally to the colder side during the day, perhaps to feed. This implies that there is a thermal barrier effect, in this case from the Oyashio front, on their behavior. The frequency of feeding events was low, although all the monitored fish dived every dawn and dusk, irrespective of the seasons or location. It is possible that these twice-daily diving patterns occurred in response to the change in ambient light at sunrise and sunset.