農業部-水產試驗所全球資訊網農業部-水產試驗所全球資訊網

本年度探討臺灣東部大目鮪(Thunnus obesus)的移動行為特徵,將彈脫型式衛星標識器(PSAT)配置於大目鮪魚體上,其中兩尾(45及50公斤)的共記錄47天和72天的行為資料,該2枚PSAT都提早脫離魚體,但前者之標識器則順利在海上尋回,並提供了完整兩分鐘一筆的精細資料。總計兩尾大目鮪記錄最深棲息深度為1,036 m,溫度僅3°C。垂直移動模式表現出的典型晝夜移動模式,表現出白天比夜間移動較廣泛,並且在黎明與日落期間為行為差異的轉則點。大目鮪白天期間主要棲息於400公尺以深,且溫度介於10-24°C。夜間期間主要棲息於表層混合層〜150 公尺。白天期間呈W型的垂直移動模式和快速的垂直移動,由大目鮪垂直移動行為資料顯示,大目鮪白天游經溫躍層的垂直運動是基於生理限制或快速的方向變化以及可能會增加攝食餌料生物機會的搜索策略,且大目鮪的垂直移動似乎跟隨著深海散射層的餌料生物棲息深度有關,以有效地利用餌料生物資源。

To learn about the movement patterns of bigeye tuna (Thunnus obesus) in eastern Taiwan, pop-up satellite archival tags (PSATs) were attached on two tuna ~50 kg and both PSATs prematurely detached and popped-up after 47 and 72 days-at-liberty. The former was physically recovered and provided fine-scale data archiving the full 47 days-at-liberty. The deepest descent recorded was 1,036 m the coldest temperature visited 3°C. Typical of the diel diving patterns displayed by many pelagic apex predators, the tagged tuna dove deeper during daytime than at nighttime and exhibited pronounced crepuscular transitions. During the daytime, the tuna spent the majority of its time above 400 m at temperatures from 10 - 24°C and at nighttime the residency was largely confined to the surface mixed-layer to ~150 m. Daytime behavior was characterized by W-shaped vertical movement patterns and fast vertical swimming speeds compared to nighttime behaviour. Like previous research, our data also suggest vertical movements traversing through the thermocline during the daytime are based on physiological constraints and/or rapid directional changes and search strategies that presumably increases the chances of prey encounters. Bigeye tuna appear to follow the diel vertical movements of prey organisms comprising the deep sound scattering layer to exploit them effectively as a resource.