Apex Predators in the Central Pacific: An Ecosystem Approach

目前渔业造成的死亡率不同于被剥削物种漫长的演化史上的任何水平，因此，渔业是一股强大的生态力量。了解渔业的影响是造成扰动的原因，这为调节远洋生态系统结构和功能的生态过程提供了重要教训。先前的项目“远洋生态系统中的顶端捕食者”以三个尺度的建模分析为基础，侧重于北太平洋中部(CNP)生态系统的营养相互作用：个体鱼类的生物能量学、捕食者-猎物相互作用和生态系统模型。金枪鱼、比目鱼和鲨鱼的长线渔业的生态影响在所有三个模式发展领域都是一个一贯的主题。主要经验是：1.确定营养个体发育的特征是为这一高度重叠利用猎物资源和行内捕食的系统建立有效模式的关键组成部分；2.渔业已经成为并将继续成为引起北大西洋金枪鱼营养结构变化的主要原因。该项目将支持第一个项目的延续和扩大。Kitchell博士及其合作者将开发可评估渔业影响在食物网动态中的作用的模型，将其扩展到包括与诸如ENSO、PDO和/或气候变化动态等大规模环境影响的相互作用，并将随后的模型用作评估可改变生态系统结构和功能的资源管理政策的基础。将追求三个主要目标：实验建模方法。他们开发了一个北太平洋中部(CNP)营养相互作用和渔业影响的模型，部分基于将种群规模数据与食物网信息和渔业发展历史相结合。在中南太平洋(CSP)存在一种生态类比，那里的渔业发展较晚。研究人员将使用CNP方法开发CSP模型，然后对渔业发展导致的营养变化进行相当于独立的、重复的分析。合并这些模型创建了一个单一的工具，允许评估在大规模环境中表达的局部影响。将渔业描述为新捕食者的等价物，可以评估食物网中的强烈相互作用和渔业效应产生的复杂反馈机制。建模以包括环境驱动因素。他们将实施由ENSO、PDO和/或全球变化效应造成的环境强迫，这些效应在我们的CNP、CSP模型和由国家生态分析与综合中心(NCEAS)赞助的类似热带太平洋(ETP)模型中表达。调查人员将使用统计方法评估种群数据中的异常情况，以此作为区分渔业和环境强迫的影响的基础，环境强迫改变了初级生产力及其在较高营养水平生产中的表现。兼捕与生态相互作用。主要的保护问题围绕着在这些远洋生态系统中兼捕受威胁或濒危的海龟、鸟类、鲨鱼和比目鱼。Kitchell博士和他的同事将使用“情景”方法模拟替代管理行动、渔业开发过程中变化的可能反应、由此产生的生态变化及其社会经济后果。Ecosim基本模式现在包括评估后者的能力，使用鱼价格的投入加上基于就业、养护和/或生态系统管理的目标的权重。

The current levels of mortality owing to fisheries are unlike anything in the long evolutionary history of exploited species and, therefore, that fisheries are a powerful ecological force. Understanding fishery effects as causes of perturbation offers important lessons about the ecological processes that regulate structure and function of pelagic ecosystems. The previous project, Apex Predators in Pelagic Ecosystems, focused on trophic interactions in the central north Pacific (CNP) ecosystem based on modeling analyses at three scales: bioenergetics of individual fish species, predator-prey interactions and ecosystem models. The ecological effects of long-line fisheries for tunas, billfishes and sharks has been a consistent theme in all three areas of model development. The major lessons were that: 1. Characterizing trophic ontogeny was a key component to building effective models for this system of strongly overlapping use of prey resources and intra-guild predation, and 2. Fisheries have become and continue as the main cause of change in trophic structure of the CNP. This project will support continuation and expansion of the first project. Dr. Kitchell and collaborators will develop models that can evaluate the role of fishery effects in food web dynamics, expand that to include interactions with large-scale environmental effects such as those due to ENSO, PDO, and/or climate change dynamics and use the consequent models as a basis for evaluating resource management policies that can change ecosystem structure and function. Three major objectives will be pursued: Experimental Approach to Modeling. They have developed a model of trophic interactions and fishery effects for the central north Pacific (CNP) based, in part, on merging population-scale data with food web information and the history of fishery development. An ecological analogue exists in the central south Pacific (CSP) where fishery development occurred at a later time. The researchers will use the CNP approach to develop a CSP model, then conduct the equivalent of an independent, replicate analysis of the trophic changes owing to fishery development. Merging these models creates a single tool that allows evaluation of local effects expressed in a large-scale context. Characterizing fisheries as the equivalent of new predators allows an evaluation of .strong interactions in food webs and the complex feedback mechanisms that emerge from fishery effects. Modeling to Include Environmental Drivers. They will implement environmental forcing due to ENSO, PDO and/or global change effects expressed in our models of the CNP, CSP and a similar model of the eastern tropical Pacific (ETP) developed through collaboration sponsored by the National Center for Ecological Analysis and Synthesis (NCEAS). The investigators will use statistical approaches that evaluate anomalies in the population data as the basis for differentiating effects of the fisheries from those of the environmental forcing that alters primary production rates and its expression in production of higher trophic levels. Bycatch and Ecological Interactions. Major conservation issues revolve around bycatch of threatened or endangered turtles, birds, sharks and billfishes in these pelagic ecosystems. Dr, Kitchell and co-workers will use a "scenarios" approach to simulation of alternative management actions, the likely responses of changes in fishery exploitation processes, their consequent ecological changes and their socioeconomic consequences. The basic Ecosim model now includes the capacity to evaluate the latter using inputs of fish prices plus weighting for goals based on employment, conservation and/or ecosystem management.