Data from: Evolutionary impact of size-selective harvesting on shoaling behavior: Individual-level mechanisms and possible consequences for natural and fishing mortality

Intensive and size-selective harvesting is an evolutionary driver of life-history as well as individual behavioral traits. Yet, whether and to what degree harvesting modifies the collective behavior of exploited species is largely unknown. We present a multi-generation harvest selection experiment with zebrafish (Danio rerio) as a model species to understand the effects of size-selective harvesting on shoaling behavior. The experimental system is based on a large-harvested (typical of most wild capture fisheries targeting larger size classes) and small-harvested (typical of specialized fisheries and gape-limited predators targeting smaller size classes) selection lines. By combining high resolution tracking of fish behavior with computational agent-based modeling we show that shoal cohesion changed in the direction expected by a trade-off between individual vigilance and the use of social cues. In particular, we document a decrease of individual vigilance in the small-harvested line, which was linked to an increase in the attention to social cues, favoring more cohesive shoals. Opposing outcomes were found for the large-harvested line, which formed less cohesive shoals. Using the agent-based model we outline possible consequences of changes in shoaling behavior for both fishing and natural mortality. The changes in shoaling induced by large size-selective harvesting may decrease fishing mortality, but increase mortality by natural predators. Our work suggests an insofar overlooked evolutionary mechanism by which size-selective harvesting can affect fishing and natural mortality of exploited fish.

高强度体型选择性捕捞是塑造生物生活史特征与个体行为性状演化的重要驱动因子。然而，目前学界对于捕捞能否以及在多大程度上改变被开发物种的集群行为，仍缺乏清晰认知。本研究以斑马鱼（Danio rerio）为模式物种，开展多世代捕捞选择实验，以探究体型选择性捕捞对集群行为的影响。本实验系统设置两类选择系：一是大型捕捞选择系（对应多数以更大体型个体为目标的野生捕捞渔业），二是小型捕捞选择系（对应以更小体型个体为目标的专业化渔业及限制张口尺寸的捕食者）。通过将鱼类行为的高分辨率追踪技术与基于智能体的计算建模相结合，我们发现集群凝聚力的变化方向符合个体警戒与社会线索利用之间的权衡预期。具体而言，小型捕捞选择系的个体警戒性出现下降，这与对社会线索的关注度提升相关，进而促使集群凝聚力增强；而大型捕捞选择系则呈现相反结果，其集群凝聚力有所下降。借助该智能体模型，我们梳理了集群行为改变对捕捞死亡率与自然死亡率的潜在影响：高强度体型选择性捕捞引发的集群行为改变，可能会降低捕捞死亡率，但会提升被捕食者的自然死亡率。本研究揭示了一种此前被忽视的演化机制——体型选择性捕捞可通过该机制影响被开发鱼类的捕捞死亡率与自然死亡率。