Data from: A quantitative framework for investigating risk of deadly collisions between marine wildlife and boats

Speed regulations of watercraft in protected areas are designed to reduce lethal collisions with wildlife but can have economic consequences. We present a quantitative framework for investigating the risk of deadly collisions between boats and wildlife. We apply encounter rate theory to demonstrate how marine mammal-boat encounter rate can be used to predict the expected number of deaths associated with management scenarios. We illustrate our approach with management scenarios for two endangered species: the Florida manatee Trichechus manatus latirostris and the North Atlantic right whale Eubalaena glacialis. We used a Monte Carlo simulation approach to demonstrate the uncertainty that is associated with our estimate of relative mortality. We show that encounter rate increased with vessel speed but that the expected number of encounters varies depending on the boating activities considered. For instance, in a scenario involving manatees and boating activities such as water skiing, the expected number of encounters in a given area (in a fixed time interval) increased with vessel speed. In another scenario in which a vessel made a transit of fixed length the expected number of encounters decreases slightly with boat speed. In both cases the expected number of encounters increased with distanced travelled by the boat. For whales, we found a slight reduction (~0.1%) in the number of encounters under a scenario where speed is unregulated; this reduction, however, is negligible, and overall expected relative mortality was ~30% lower under the scenario with speed regulation. The probability of avoidance by the animal or vessel was set to 0 because of lack of data, but we explored the importance of this parameter on the model predictions. In fact, expected relative mortality under speed regulations decreases even further when the probability of avoidance is a decreasing function of vessel speed. By applying encounter rate theory to the case of boat collisions with marine mammals, we gained new insights about encounter processes between wildlife and watercraft. Our work emphasizes the importance of considering uncertainty when estimating wildlife mortality. Finally, our findings are relevant to other systems and ecological processes involving the encounter between moving agents.

保护区内的船舶限速规定旨在降低与野生动物发生致命碰撞的风险，但此类管控措施可能带来经济影响。我们提出了定量框架（quantitative framework），用于探究船舶与野生动物发生致命碰撞的风险。我们运用相遇率理论（encounter rate theory），阐明了如何通过海洋哺乳动物与船舶的相遇率，预测不同管理情景下的预期死亡数量。我们以两种濒危物种为例展示了该方法的应用：佛罗里达海牛（Trichechus manatus latirostris）以及北大西洋露脊鲸（Eubalaena glacialis）。我们采用蒙特卡洛模拟（Monte Carlo simulation）方法，展示了相对死亡率估算中伴随的不确定性。研究表明，相遇率随船舶航速提升而升高，但预期相遇次数会因所考量的船舶活动类型而异。例如，在涉及海牛与滑水（water skiing）类船舶活动的情景中，给定区域内固定时段的预期相遇次数会随船舶航速提升而增加；而在船舶开展固定航程航行的另一情景中，预期相遇次数则会随航速提升小幅下降。在两种情景下，预期相遇次数均会随船舶航行距离增加而上升。针对露脊鲸的研究显示，在无航速限制的情景下，相遇次数仅出现约0.1%的小幅减少；但该降幅可忽略不计，且整体相对死亡率在实施航速限制的情景中降低了约30%。由于缺乏相关数据，我们将动物或船舶的避让概率设为0，但我们探究了该参数对模型预测结果的重要性。事实上，当避让概率随船舶航速提升而降低时，航速限制下的预期相对死亡率会进一步下降。通过将相遇率理论应用于海洋哺乳动物与船舶碰撞的场景，我们对野生动物与船舶的相遇过程获得了新的认知。我们的研究强调了在估算野生动物死亡率时考量不确定性的重要性。最后，我们的研究结果对其他涉及移动主体间相遇的系统与生态过程均具有参考价值。