Detection of pelagic habitat hotspots for skipjack tuna in the Gulf of Bone-Flores Sea, southwestern Coral Triangle tuna, Indonesia

Using remote sensing of sea surface temperature (SST), sea surface height anomaly (SSHA) and chlorophyll-a (Chl-a) together with catch data, we investigated the detection and persistence of important pelagic habitat hotspots for skipjack tuna in the Gulf of Bone-Flores Sea, Indonesia. We analyzed the data for the period between the northwest and southeast monsoon 2007–2011. A pelagic hotspot index was constructed from a model of multi-spectrum satellite-based oceanographic data in relation to skipjack fishing performance. Results showed that skipjack catch per unit efforts (CPUEs) increased significantly in areas of highest pelagic hotspot indices. The distribution and dynamics of habitat hotspots were detected by the synoptic measurements of SST, SSHA and Chl-a ranging from 29.5° to 31.5°C, from 2.5 to 12.5 cm and from 0.15 to 0.35 mg m-3, respectively. Total area of hotspots consistently peaked in May. Validation of skipjack CPUE predicted by our model against observed data from 2012 was highly significant. The key pelagic habitat corresponded with the Chl-a front, which could be related to the areas of relatively high prey abundance (enhanced feeding opportunity) for skipjack. We found that the area and persistence of the potential skipjack habitat hotspots for the 5 years were clearly identified by the 0.2 mg m-3 Chl-a isopleth, suggesting that the Chl-a front provides a key oceanographic indicator for global understanding on skipjack tuna habitat hotspots in the western tropical Pacific Ocean, especially within Coral Triangle tuna.

本研究整合海面温度（Sea Surface Temperature, SST）、海面高度异常（Sea Surface Height Anomaly, SSHA）与叶绿素a（Chlorophyll-a, Chl-a）的遥感观测数据及渔获统计数据，针对印度尼西亚波尼湾-弗洛勒斯海海域内鲣鱼的关键中上层生境热点的识别与持续性展开系统调查。本研究分析了2007至2011年西北季风与东南季风时段的全部数据集，基于关联鲣鱼捕捞绩效的多光谱卫星海洋学数据模型构建了中上层生境热点指数。研究结果表明，在中上层生境热点指数最高的海域，鲣鱼单位捕捞努力量渔获量（Catch Per Unit Effort, CPUE）显著升高。通过同步观测SST、SSHA与Chl-a的分布特征——其中SST区间为29.5℃至31.5℃，SSHA区间为2.5至12.5 cm，Chl-a区间为0.15至0.35 mg·m⁻³——本研究成功识别了生境热点的空间分布与动态变化规律。热点海域的总面积在每年5月始终达到峰值。利用2012年的实测渔获数据对本模型预测的鲣鱼CPUE进行验证，结果具有高度统计学显著性。核心中上层生境与叶绿素锋面（Chl-a front）高度契合，这一现象或与鲣鱼的猎物丰度提升、觅食机会增加的海域密切相关。本研究发现，通过0.2 mg·m⁻³的Chl-a等值线，可清晰识别出2007至2011年这5年间潜在鲣鱼生境热点的面积与持续性特征，表明叶绿素锋面可为全球热带西太平洋（尤其是珊瑚三角区金枪鱼海域）的鲣鱼生境热点研究提供关键海洋学指示指标。