Herring supports Northeast Pacific predators and fisheries: Insights from ecosystem modelling and management strategy evaluation

This paper analyzes the trophic role of Pacific herring, the potential consequences of its depletion, and the impacts of alternative herring fishing strategies on a Northeast Pacific food web in relation to precautionary, ecosystem-based management. We used an Ecopath with Ecosim ecosystem model parameterized for northern British Columbia (Canada), employing Ecosim to simulate ecosystem effects of herring stock collapse. The ecological impacts of various herring fishing strategies were investigated with a Management Strategy Evaluation algorithm within Ecosim, accounting for variability in climatic drivers and stock assessment errors. Ecosim results suggest that herring stock collapse would have cascading impacts on much of the pelagic food web. Management Strategy Evaluation results indicate that herring and their predators suffer moderate impacts from the existing British Columbia harvest control rule, although more precautionary management strategies could substantially reduce these impacts. The non-capture spawn-on-kelp fishery, traditionally practiced by many British Columbia and Alaska indigenous peoples, apparently has extremely limited ecological impacts. Our simulations also suggest that adopting a maximum sustainable yield management strategy in Northeast Pacific herring fisheries could generate strong, cascading food web effects. Furthermore, climate shifts, especially when combined with herring stock assessment errors, could strongly reduce the biomasses and resilience of herring and its predators. By clarifying the trophic role of Pacific herring, this study aims to facilitate precautionary fisheries management via evaluation of alternative fishing strategies, and thereby to inform policy tradeoffs among multiple ecological and socioeconomic factors.本研究分析了太平洋鲱鱼（Pacific herring）的营养级作用、其种群枯竭的潜在后果，以及在预防性基于生态系统的管理框架下，各类替代鲱鱼捕捞策略对东北太平洋食物网的影响。本研究采用针对加拿大不列颠哥伦比亚省北部海域参数化的Ecopath with Ecosim生态系统模型，并借助Ecosim模块模拟鲱鱼种群崩溃对生态系统的效应。研究依托Ecosim内置的管理策略评估（Management Strategy Evaluation）算法，探究各类鲱鱼捕捞策略的生态影响，并将气候驱动因子变异与种群评估误差纳入考量。Ecosim模拟结果显示，鲱鱼种群崩溃将对绝大多数水层食物网产生级联效应。管理策略评估结果表明，尽管采用更具预防性的管理策略可大幅降低此类影响，但现行不列颠哥伦比亚省捕捞控制规则仍会对鲱鱼及其捕食者造成中等程度的影响。由不列颠哥伦比亚省与阿拉斯加诸多原住民族群传统传承的非捕获式海藻附卵捕捞作业，其生态影响显然极为有限。本研究的模拟结果还显示，在东北太平洋鲱鱼渔业中采用最大可持续产量（maximum sustainable yield）管理策略，将引发显著的食物网级联效应。此外，气候变迁尤其是与鲱鱼种群评估误差叠加时，将大幅降低鲱鱼及其捕食者的生物量与种群恢复力。本研究通过阐明太平洋鲱鱼的营养级生态作用，旨在借助对替代捕捞策略的评估推动预防性渔业管理，进而为平衡多重生态与社会经济因素的政策权衡提供科学依据。