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控制鱼类种群动态的生态条件在很长一段时间内保持稳定。在许多区域，捕食鱼类的关键物种出现了非常大的系统性趋势，关键猎物物种出现了较大的波动。在研究捕食者-猎物相互作用对具有商业价值和娱乐价值的物种的可能影响方面，已经进行了大量的理论模拟研究。然而，对开发种群评估建模方法和管理战略评估(MSE)方法的关注相对较少，这些方法可以在关键娱乐和商业鱼类的关键猎物和捕食者物种发生重大明显变化的情况下向渔业管理者和政策制定者提供直接建议。我试图调查捕食者-猎物相互作用的系统性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方法来实现这一点，在该方法中，我将建立新的鱼类种群种群动力学模型，该模型考虑了在一些加拿大渔业中捕食者和猎物种群的变化可能产生的影响，在这些渔业中，关键捕食者和/或猎物种群最近发生了实质性变化。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以及猎物物种丰度变化对这些鱼类种群增长率变化的可能影响的假设。因此，我提出的研究计划的长期目标是使用管理策略评估(MSE)框架来调查捕食者-猎物相互作用对鱼类种群的影响。我试图建立种群动力学模型，使用贝叶斯统计技术来检验捕食者-猎物相互作用对捕捞鱼类种群种群动态的影响的假设，并将这些模型应用于中小企业，以确定对未来捕食率和猎物可获得性可能发生变化的情景具有稳健性的政策选择。我计划测试以下假设：(A)鳍足类(例如海豹物种)种群丰度和(B)饲料物种可获得性的大的系统性变化将通过生长和自然死亡率(M)的变化来改变渔业开发对捕捞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和历史和可能的未来趋势如何能够共同改变(A)种群动态，(B)通常用于指导政策建议的最大可持续产量(MSY)参考点，以及(C)不同管理方法对各种捕捞鱼种的适用性。此外，我将研究(2)如何设计管理方法，以适应关键捕食者和猎物丰度的系统性变化，这可能会改变鱼类种群对开发的适应能力。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水域岩鱼种群的政策选择。项目2：使用MSE方法评估在饲料物种丰度变化较大的情况下顶端捕食者的政策选择：弗雷泽河下游白鲟鱼。在这些案例研究中，将评估关键捕食者和猎物种群的系统性变化如何影响鱼类种群的情景，以便确定对这种变化作出适当反应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.