Across borders: external factors and prior behavior influence North Pacific albatross associations with fishing vessels

1. Understanding encounters between marine predators and fisheries across national borders and outside national jurisdictions offers new perspectives on unwanted interactions to inform ocean management and predator conservation. Although seabird-fisheries overlap has been documented at many scales, remote identification of vessel encounters has lagged because vessel movement data often is lacking. 2. Here, we reveal albatross-fisheries associations throughout the North Pacific Ocean. We identified commercial fishing operations using Global Fishing Watch data and algorithms to detect fishing vessels. We compiled GPS tracks of adult black-footed (Phoebastria nigripes) and Laysan (P. immutabilis) albatrosses, and juvenile short-tailed albatrosses (P. albatrus). We quantified albatross-vessel encounters based on the assumed distance that birds perceive a vessel (≤30km), and associations when birds approached vessels (≤3km). For each event we quantified bird behavior, environmental conditions, and vessel characteristics and then applied Boosted Regression Tree models to identify drivers and the duration of these associations. 3. In regions of greater fishing effort short-tailed and Laysan albatross associated with fishing vessels more frequently. However, fishing method (e.g. longline, trawl) and flag nation did not influence association prevalence nor the duration short-tailed albatross attended fishing vessels. Laysan albatross were more likely to approach longer vessels. Black-footed albatross were the most likely to approach vessels (61.9%), but limited vessel encounters (n=21) prevented evaluation of meaningful explanatory models for this species of high bycatch concern. 4. Temporal variables (time of day and month) and bird behavioral state helped explain when short-tailed albatross were in close proximity to a vessel, but environmental conditions were more important for explaining interaction duration. Laysan albatross were more likely to associate with vessels while searching and during the last 60% (by time) of their trips. 5. Our results provide specific species-fisheries insight regarding contributing factors of high-risk associations that could lead to bycatch of albatross within national waters and on the high-seas. 6. Policy implications. Given the global availability of Global Fishing Watch data, our methods can be applied to other marine predators to identify spatio-temporal patterns, vessel specific attributes, and predator behaviors associated with fishing vessel associations thus enabling predictive modeling and targeted mitigation measures.

1. 解析跨国境及国家管辖范围以外海域的海洋捕食者与渔业的交互关系，可为海洋管理与捕食者保育提供应对不良交互的新视角。尽管已有多尺度研究记录了海鸟与渔业活动的空间重叠，但受限于船舶移动数据的普遍缺失，远程识别船舶与捕食者的交互仍存在显著滞后。
2. 本研究揭示了北太平洋全域的信天翁与渔业的关联模式。我们依托Global Fishing Watch（全球渔业监测）数据集与船舶检测算法，识别了商业渔业作业活动；收集了成年黑脚信天翁（Phoebastria nigripes）、莱桑信天翁（P. immutabilis）以及短尾信天翁幼鸟（P. albatrus）的GPS轨迹数据。我们基于鸟类感知船舶的假设阈值距离（≤30千米）量化信天翁与船舶的交互事件，并以鸟类靠近船舶的阈值距离（≤3千米）定义二者的关联关系；针对每一次交互事件，我们量化了鸟类行为、环境条件与船舶特征，并采用提升回归树（Boosted Regression Tree）模型识别了此类关联的驱动因子与持续时长。
3. 在渔业作业强度更高的海域，短尾信天翁与莱桑信天翁与船舶的关联频率更高。然而，渔业作业方式（如延绳钓、拖网）与船舶挂旗国，并未对短尾信天翁的关联发生率或其伴随船舶的持续时长产生显著影响；莱桑信天翁更倾向于靠近长度更长的船舶。黑脚信天翁是最易靠近船舶的物种（占比61.9%），但由于可观测的船舶交互事件仅21次，无法针对这一具有较高副渔获物（bycatch）关注度的物种构建具有统计学意义的解释模型。
4. 时间变量（时段与月份）与鸟类行为状态，可解释短尾信天翁近距离靠近船舶的时间分布，但环境条件对解释交互持续时长更为关键。莱桑信天翁更易在觅食搜索阶段以及航程的最后60%时段内与船舶产生关联。
5. 本研究结果针对特定物种与渔业的高风险关联提供了精细化见解，此类关联可能导致信天翁在国家管辖海域及公海（high-seas）发生副渔获物捕获。
6. 政策启示：鉴于Global Fishing Watch数据集的全球可获取性，本研究方法可推广应用于其他海洋捕食者，以识别与船舶关联相关的时空模式、船舶专属特征及捕食者行为，从而支持预测建模与针对性减缓措施的制定。