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Analysis of sinking death using video images of the swimming performance of Pacific Bluefin tuna (Thunnus orientalis) larvae
Aquacultural Engineering ( IF 4 ) Pub Date : 2020-08-01 , DOI: 10.1016/j.aquaeng.2020.102099
Y. Ina , T. Takagi , S. Miyashita , M. Kurata , T. Honryo , Y. Sawada , H. Fukuda , S. Torisawa

Abstract In this study, we aimed to clarify the mechanism of sinking death during the larval stage of Pacific Bluefin tuna Thunnus orientalis by investigating the effects of swimming performance on sinking death, using a behavioral approach. Swimming performance was examined 3–9 days after hatching (DAH) under day and night light conditions in cuboid experimental tanks. Swimming behavior variables such as swimming speed and swimming angle were measured under both light conditions. Larvae in the daytime experiment and larvae with inflated swim bladders at night were distributed on the surface layer of the water column. In contrast, larvae with uninflated swim bladders at night were frequently observed swimming vertically or sinking to the bottom of the tank. Larvae with inflated swim bladders at night were always distributed beneath the surface until the next morning (survival rates were 100 %). However, larvae with uninflated swim bladders at night swam upward repeatedly and later sank to the bottom of the tank (survival rates were 60 % and 38 % at 5 and 9 DAH, respectively). Larvae with uninflated swim bladders were not always able to maintain their swimming depth by swimming until the next morning. Additionally, their swimming speed and vertical swimming frequency (ratio) depended on the illumination and swim bladder conditions. Our findings show that larvae with uninflated swim bladders at night were associated with a higher risk of sinking death. The swimming energy capacity of Pacific Bluefin tuna larvae, which indicates the total amount of the energy that enables individuals to swim throughout the night without feeding, was found to be linked to sinking death.

中文翻译:

利用太平洋蓝鳍金枪鱼(Thunnus orientalis)幼虫游泳表现的视频图像分析沉没死亡

摘要 在本研究中,我们旨在通过使用行为方法研究游泳表现对沉没死亡的影响,阐明太平洋蓝鳍金枪鱼 Thunnus orientalis 幼体阶段沉没死亡的机制。孵化后 3-9 天(DAH)在长方体实验池的昼夜光照条件下检查游泳性能。在两种光照条件下测量游泳行为变量,如游泳速度和游泳角度。白天实验的幼虫和夜间膨胀的鱼鳔幼虫分布在水体的表层。相比之下,经常观察到夜间未充气的鱼鳔幼虫垂直游动或沉入水箱底部。夜间膨胀的鱼鳔幼虫总是分布在水面下,直到第二天早上(成活率为 100%)。然而,带有未充气鳔的幼虫在夜间反复向上游动,然后沉入水箱底部(在 5 天和 9 天时的存活率分别为 60% 和 38%)。带有未充气的鱼鳔的幼虫并不总是能够通过游泳直到第二天早上来保持它们的游泳深度。此外,它们的游泳速度和垂直游泳频率(比率)取决于光照和鱼鳔条件。我们的研究结果表明,夜间未充气的鱼鳔幼虫与较高的沉没死亡风险相关。太平洋蓝鳍金枪鱼幼体的游泳能量,
更新日期:2020-08-01
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