Evaluating fisheries management options under large systematic changes in predator-prey interactions

最常用于提供渔业管理咨询意见的定量模型假定长期控制鱼类种群动态的生态条件是稳定的。在许多地区，捕食鱼类的关键物种出现了非常大的系统性趋势，关键猎物物种的波动也很大。已有相当多的理论建模研究来研究捕食者-猎物相互作用对商业和娱乐价值物种的可能影响。然而，在主要休闲和商业鱼类的主要猎物和捕食者物种发生明显变化的情况下，很少有人关注开发种群评估建模方法和管理战略评价方法，这些方法可以为渔业管理者和决策者提供直接建议。我试图调查捕食者-猎物相互作用的系统变化对各种加拿大渔业鱼类种群动态的影响，在这些渔业中，猎物和捕食者种群似乎发生了实质性变化。我将使用MSE方法来实现这一目标，在这种方法中，我将建立新的鱼类种群种群动态模型，这些模型将解释加拿大一些渔业中捕食者和猎物种群的变化可能产生的影响，这些渔业最近在主要捕食者和/或猎物物种种群中发生了重大变化。我将试图测试关于捕食者物种丰度和捕食率变化对自然死亡率的可能影响的假设，以及这些鱼类种群的猎物物种丰度变化对生长率变化的可能影响。因此，我提出的研究计划的长期目标是利用管理策略评估（MSE）的框架来研究捕食者-猎物相互作用对鱼类种群的影响。我试图开发种群动态模型，使用贝叶斯统计技术来测试关于捕食者-猎物相互作用对收获鱼类种群动态的影响的假设，并将这些模型应用于mse中，以确定对未来捕食率和猎物可用性的合理变化情景稳健的政策选择。我计划测试以下假设，即：(a)鳍类（如海豹）种群丰度和(b)饲料物种可用性的大系统变化将通过变化（如生长和自然死亡率）来改变渔业开发对收获鱼类种群动态的影响。为了开展这项研究，我将调查(1)捕食风险和被捕食物种丰度的空间异质性、历史和可能的未来趋势如何共同改变(a)种群动态，(b)通常用于指导政策建议的最大可持续产量参考点，以及(c)不同管理方法对各种捕捞鱼类的适用性。此外，我将研究(2)如何设计管理方法，以适应可能改变鱼类种群对开发的适应能力的主要捕食者和猎物丰度的系统变化。我计划进行两个案例研究：项目1：使用MSE方法评估长期枯竭的不列颠哥伦比亚省内水岩鱼种群的政策选择。项目#2：在饲料物种丰度发生巨大变化的情况下，使用MSE方法评估顶端捕食者的政策选择：弗雷泽河下游白鲟。在这些案例研究中，将评估主要捕食者和猎物种群的系统变化如何影响鱼类种群的情景，以便确定适当应对这种变化的渔业监测和捕捞控制政策选择。

The quantitative models most commonly applied to provide fisheries management advice presume stability in ecological conditions governing fish population dynamics over long periods of time. In many regions there have been very large systematic trends in key species that prey on fishes and large fluctuations in key prey species. There has been considerable theoretical modeling research into studying the possible impacts of predator-prey interactions on commercially and recreationally valuable species. However, there has been relatively little attention given to developing stock assessment modeling approaches and management strategy evaluation (MSE) approaches that can offer direct advice to fisheries managers and policy makers in situations where there have been large apparent changes in key prey and predator species of key recreational and commercial fishes. I seek to investigate the influence of systematic changes in predator-prey interactions on fish population dynamics for a variety of Canadian fisheries in which there appears to have been substantial changes in the prey and predator populations. I will do so using a MSE approach in which I will build new population dynamics models of fish populations that account for the possible influence of changes in predator and prey populations in a number of Canadian fisheries where there have been substantial recent changes in key predator and/or prey species populations. I will seek to test hypotheses about the possible effects of changes in predator species abundance and predation rates on natural mortality rates and changes in prey species abundance on changes in growth rates for these fish populations. The long-term objective of my proposed research program is thus to investigate the influence of predator-prey interactions on fish populations using the framework of management strategy evaluation (MSE). I seek to develop population dynamics models, use Bayesian statistical techniques to test hypotheses about the influence of predator-prey interactions on the population dynamics of harvested fish populations and apply these models in MSEs to identify policy options that are robust to scenarios for plausible changes in future predation rates and prey availability. I plan to test the hypotheses that large systematic changes in (a) pinniped (e.g., seal species) population abundance and (b) forage species availability will modify the influence of fisheries exploitation on the population dynamics of harvested fish populations via changes in, e.g., growth and natural mortality rates (M). To undertake the research I will investigate how (1) spatial heterogeneity and historic and possible future trends in predation risk and the abundance of prey species can jointly modify (a) the population dynamics, (b) the maximum sustainable yield (MSY) reference points that are commonly used to guide policy advice, and (c) the suitability of different management approaches for a variety of harvested fish species. In addition I will investigate (2) how management approaches can be designed to adapt to systematic changes in the abundance of key predator and prey that may modify a fish stock’s resilience to exploitation. I plan two case studies: Project #1: Using an MSE approach to evaluate policy options for chronically-depleted B.C. inside water rockfish stocks. Project #2: Using a MSE approach to evaluate policy options for an apex predator under large changes in forage species abundance: Lower Fraser River white sturgeon. In these case studies, scenarios on how systematic changes in key predator and prey populations can affect fish stocks will be assessed in order to identify fisheries monitoring and harvest control policy options that respond appropriately to such changes.