Opening the tap: increased riverine connectivity strengthens marine food web pathways.

Reduction of ecosystem connectivity has long-lasting impacts on food webs. Anadromous fish, which migrate from marine to freshwater ecosystems to complete reproduction, have seen their historically larger ecosystem role undercut by widespread riverine habitat fragmentation and other impacts mainly derived from anthropogenic sources. The result has been extensive extirpations and increased susceptibility to a suite of environmental factors that currently impede recovery. Under this present-day context of reduced productivity and connectivity, aggressive management actions and enforcement of catch limits including bycatch caps and complete moratoria on harvest have followed. What remains less understood are the implications of changes to food webs that co-occurred. What benefits restoration could provide in terms of ecosystem functioning in relation to economic costs associated with dam removal and remediation is unknown and can limit the scope and value of restoration activities. Here we...

生态系统连通性（ecosystem connectivity）的降低会对食物网（food webs）产生持久影响。溯河洄游鱼类（Anadromous fish）——即从海洋洄游至淡水生态系统完成繁殖的鱼类——其长期以来在生态系统中发挥的更为广泛的作用，正因大范围的河流生境破碎化（riverine habitat fragmentation）以及其他主要源自人类活动的干扰而遭到削弱。其后果是大量局部灭绝（extirpations）事件的发生，且种群对各类环境因子的易感性显著上升，当前这些因子正阻碍着种群的恢复。在当下生产力与连通性均有所下降的背景下，相关管理方已采取强力管理措施，并严格落实捕捞限制政策，包括设定副渔获上限（bycatch caps）与实施全面禁捕（complete moratoria on harvest）。但目前我们对同期发生的食物网变化所带来的影响仍知之甚少。目前尚不明确，相较于大坝拆除（dam removal）与生态修复（remediation）所需的经济成本，生态恢复能为生态系统功能带来何种益处，这一不确定性会限制修复活动的开展范围与价值。本文我们……