A spatially resolved ecosystem model for the assessment of fisheries

我们的目标是构建一个空间多物种生态系统模型，重点关注北欧大陆架(北纬47度至62度，东经零下12度至10度)商业开发的鱼类。模型中的物种或功能基团将被置于生物细节的层次结构中。在最高或“结构化”的细节水平上，目标物种将由相互作用的长度结构种群来表示，在这些种群中，控制个体生长、捕食、繁殖和死亡的过程得到了充分的规定。在中间水平上，将是“非结构化”的生态系统元素，如底栖无脊椎动物和浮游动物，它们被动态地表示，但没有生活史细节。在最低的细节水平，我们将有顶级捕食者(鲸目动物和海鸟)和捕鱼死亡率的‘驱动因素’，这些没有建模，但对生态系统的其余部分提供了强迫功能。该模型将在不同的空间尺度上运行，从一系列链接的区域模型到覆盖整个领域的中等尺度网格。物理环境将从海洋环流模型中获得，温度用于驱动生长速度等依赖温度的过程，流动决定浮游生物、浮游动物和鱼苗的运输。该模型将使用渔业调查数据、浮游动物和底栖动物产量的估计以及顶级捕食者的消耗量估计来进行参数化。由于顶级捕食者可能对生态和商业产生重要影响，一项联合提案(结合学生身份)将旨在为这些驱动因素产生更好的空间估计。自由参数将由马尔可夫链蒙特卡罗(MCMC)方法估计。我们将借鉴斯特拉斯克莱德大学开发的一系列计算创新，以明确处理具有生活史、结构和生长变异性的种群的空间模型。我们将使用ECopath软件作为辅助工具，为我们系统中物种之间的质量转移构建区域预算，然后将其与我们的模型预测的结果进行比较。我们的建模方法与其他生态系统建模方法有很大不同，例如ECopath with Ecosim(EWE)，后者经常被认为是渔业基于生态系统的管理的前进方向。因此，我们建议的一个关键部分是进行一项涉及区域生态系统模型的比较研究，以确定替代方法的优势和劣势。

We aim to construct a spatial multi-species ecosystem model focused on commercially exploited fish in the northern European shelf (47 to 62 degrees N, and -12 to 10 degrees E). Species or functional groups within the model will be placed within a hierarchy of biological detail. At the highest, or 'structured', level of detail the target species will be represented by interacting length-structured populations in which the processes governing individual growth, predation, reproduction, and mortality are fully specified. At an intermediate level will be 'unstructured' ecosystem elements, such as benthic invertebrates and zooplankton, that are represented dynamically but without life history detail. At the lowest level of detail we will have the 'drivers' of top predators (cetacean and seabird) and fishing mortality, which are not modelled but provide forcing functions to the rest of the ecosystem. The model will be run at various spatial scales, from a series of linked regional models through to medium-scale grid covering the entire domain. The physical environment will be obtained from an ocean circulation model, with temperatures used to drive temperature-dependent process such as growth rate, and flows determining the transport of plankton zooplankton and fish larvae. The model will be parameterised using fishing survey data, and estimates of zooplankton and benthic production, and estimates of consumption by top predators. Due to the potential for ecologically and commercially important impacts by top predators a joint proposal (for a tied studentship) will aim to produce improved spatial estimates for these drivers. Free parameters will be estimated by Markov chain Monte Carlo (MCMC) methods. We will draw on a range of computational innovations developed at Strathclyde University for dealing with explicitly spatial models of populations with life history structure and growth variability. We will use the Ecopath software as an aid to constructing regional budgets for mass transfer between the species in our system, and which can then be compared to those predicted by our model. Our modelling approach differs substantially from alternative ecosystem modelling methods, such as Ecopath with Ecosim (EwE), that are frequently advocated as the way forward for ecosystem-based management in fisheries. A key part of our proposal is therefore a comparative study involving EwE regional ecosystem models, with a view to identifying the strengths and weaknesses of alternative methodologies.