Abstract Over recent years the summer feeding distribution of Northeast Atlantic mackerel (NEAM, Scomber scombrus) has expanded from its traditional core in the Norwegian Sea, northwards towards Svalbard, and westward as far as Greenland. Food availability, temperature and an increase in spawning stock biomass (SSB) are reported to be possible drivers of the distribution, but quantifying the relative contributions of these factors is difficult. Previously we developed a bioenergetics individual-based model (IBM) that uses satellite-derived maps of food availability and temperature to predict NEAM population dynamics. Here, we extend the model to explore the ways in which individuals move in search of food in the summer. We construct models of four possible search mechanisms differing in (1) the extent of the area over which individuals can perceive the environment; and (2) whether or not individuals respond to the local density of conspecifics by avoiding areas in which competition is more intense. We report that the best matches to available data over 2007–2015 are obtained when the local density of competitors is taken into account, and individuals move in response to local gradients in feeding opportunities. To determine whether the IBM is able to reproduce the observed north and westward expansion, we record total distribution area, and predicted centre of gravity in terms of latitude and longitude, over 2005–2015. The IBM successfully predicts an increase in distribution area, and a northward shift in centre of gravity, over the time series. It also predicts a westward shift in centre of gravity, but to a much lesser extent than has been observed in surveys and the fishery. The inability of our IBM to capture the full extent of the westward expansion suggests that it does not account for all relevant drivers of the NEAM summer distribution. Going forward we hope that our model can be: (1) extended to explore additional drivers of the summer distribution (e.g. currents); and (2) used in a strategic capacity to predict how the NEAM stock may respond to future climate and management scenarios.

中文翻译：

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用基于个体的机械模型模拟东北大西洋鲭鱼夏季摄食分布

摘要 近年来，东北大西洋鲭鱼（NEAM，Scomber scombrus）的夏季摄食分布从其在挪威海的传统核心向北扩展至斯瓦尔巴群岛，向西扩展至格陵兰。据报道，食物供应、温度和产卵种群生物量 (SSB) 的增加可能是分布的驱动因素，但很难量化这些因素的相对贡献。此前，我们开发了一个基于生物能量学个体的模型 (IBM)，该模型使用卫星衍生的食物可用性和温度地图来预测 NEAM 种群动态。在这里，我们扩展模型以探索个体在夏季寻找食物的方式。我们构建了四种可能的搜索机制的模型，它们的不同在于（1）个人可以感知环境的区域的范围；(2) 个体是否通过避开竞争更激烈的区域来对局部同种密度做出反应。我们报告说，当考虑竞争者的本地密度时，可以获得与 2007-2015 年可用数据的最佳匹配，并且个体根据喂养机会的局部梯度而移动。为了确定 IBM 是否能够重现观测到的北向和向西扩张，我们记录了 2005-2015 年的总分布面积，并根据经纬度预测了重心。IBM 成功地预测了时间序列中分布区域的增加和重心的北移。它还预测重心向西移动，但程度比调查和渔业中观察到的要小得多。我们的 IBM 无法捕获向西扩展的全部范围，这表明它没有考虑到 NEAM 夏季分布的所有相关驱动因素。展望未来，我们希望我们的模型可以： (1) 扩展以探索夏季分布的其他驱动因素（例如洋流）；(2) 用于预测 NEAM 种群如何应对未来气候和管理情景的战略能力。展望未来，我们希望我们的模型可以： (1) 扩展以探索夏季分布的其他驱动因素（例如洋流）；(2) 用于预测 NEAM 种群如何应对未来气候和管理情景的战略能力。展望未来，我们希望我们的模型可以： (1) 扩展以探索夏季分布的其他驱动因素（例如洋流）；(2) 用于预测 NEAM 种群如何应对未来气候和管理情景的战略能力。