Albacore tuna (Thunnus alalunga) exhibit patchy concentrations associated with biological process at a wide range of spatial scales, resulting in variations in their catchability by fishing gears. Here, we investigated the association of catch variation for pelagic longlines in the South Pacific Ocean with oceanographic mesoscale structures (in horizontal dimension) and ambient conditions (in vertical dimension). The distribution of albacore tuna as indicated by catch per unit effort (CPUE) of longlines was significantly related to the presence of mesoscale structures, with higher CPUE found at locations closer to thermal fronts and with greater gradient magnitudes, as well as areas marked by peripheral contour line of the anticyclone indicated by Sea Surface Height Anomalies ~0.05 m. Surface mesoscale current velocity had the negative effect on the catch, probably as a result of decreased catchability by shoaling the hook depth. Vertical distribution of albacore in the survey region of South Pacific Ocean was hardly restricted by ambient temperature and oxygen concentration, though effect of ambient temperature was relevant and showed a negatively linear correlation with CPUE at the range of 20–24°C. On the contrary, albacore distribution was evidently dominated by the water depth and showed strong preference on water depth of 200 m, which was likely a representative feeding layer. The presence of prey resources and their accessibility by albacore revealed by mesoscale structures in the biological and physical processes, and catchability determined by the location of the baited hooks comprehensively contribute to the variability of catch.

中文翻译：

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中尺度海洋结构和环境条件对南太平洋延绳钓渔业中长鳍金枪鱼产量的影响

长鳍金枪鱼（Thunnus alalunga）在广泛的空间尺度上表现出与生物过程相关的斑片状浓度，导致渔具的捕捞能力发生变化。在这里，我们研究了南太平洋中上层延绳钓渔获量变化与海洋中尺度结构（水平方向）和环境条件（垂直方向）的关系。延绳钓每单位工作量捕获的长鳍金枪鱼的分布与中尺度结构的存在显着相关，在靠近热锋且梯度幅度较大的区域发现了中尺度结构，而外围区域则标有海平面高度异常〜0.05 m表示反气旋的轮廓线。表面中尺度电流对捕获量有负面影响，可能是由于浅浅的钩子深度而降低了可捕获性。尽管环境温度的影响是相关的，并且在20–24°C范围内与CPUE呈负线性相关关系，但长鳍科克在南太平洋调查区域的垂直分布几乎不受环境温度和氧气浓度的限制。相反，长鳍金枪鱼的分布明显受水深的支配，并且对200 m的水深表现出强烈的偏好，这可能是一个典型的进食层。猎物资源的存在及其在长足动物的生物和物理过程中的中尺度结构所揭示的长鳍金枪鱼的可及性，以及由饵钩的位置决定的可捕性，全面地影响了捕捞的可变性。尽管环境温度的影响是相关的，并且在20–24°C范围内与CPUE呈负线性相关关系，但长鳍科克在南太平洋调查区域的垂直分布几乎不受环境温度和氧气浓度的限制。相反，长鳍金枪鱼的分布明显受水深的支配，并且对200 m的水深表现出强烈的偏好，这很可能是典型的觅食层。猎物资源的存在及其在长足动物的生物和物理过程中的中尺度结构所揭示的长鳍金枪鱼的可及性，以及由饵钩的位置决定的可捕性，全面地影响了捕捞的可变性。尽管环境温度的影响是相关的，并且在20–24°C范围内与CPUE呈负线性相关关系，但长鳍科克在南太平洋调查区域的垂直分布几乎不受环境温度和氧气浓度的限制。相反，长鳍金枪鱼的分布明显受水深的支配，并且对200 m的水深表现出强烈的偏好，这很可能是典型的觅食层。猎物资源的存在及其在长足动物的生物和物理过程中的中尺度结构所揭示的长鳍金枪鱼的可及性，以及由饵钩的位置决定的可捕性，全面地影响了捕捞的可变性。