Data from: Life stage and species identity affect whether habitat subsidies enhance or simply redistribute consumer biomass

1. Quantifying the response of mobile consumers to changes in habitat availability is essential for determining the degree to which population-level productivity is habitat limited rather than regulated by other, potentially density-independent factors. 2. Over landscape scales, this can be explored by monitoring changes in density and foraging as habitat availability varies. As habitat availability increases, densities may: (1) decrease (unit-area production decreases; weak habitat limitation); (2) remain stable (unit-area production remains stable; habitat limitation); or (3) increase (unit-area production increases; strong habitat limitation). 3. We tested the response of mobile estuarine consumers over five months to changes in habitat availability in situ by comparing densities and feeding rates on artificial reefs that were or were not adjacent to neighboring artificial reefs or nearby natural reefs). 4. Using either constructed or natural reefs to manipulate habitat availability, we documented three-fold density decreases among juvenile stone crabs as habitat increased (i.e. weak habitat imitation). However, for adult stone crabs, density remained stable across treatments, demonstrating that habitat limitation presents a bottleneck in this species’ later life history. Oyster toadfish densities also did not change with increasing habitat availability (i.e. habitat limitation), but densities of other cryptic fishes decreased as habitat availability increased (i.e. weak limitation). Feeding and abundance data suggested that some mobile fishes experience habitat limitation, or, potentially in one case, strong limitation across our habitat manipulations. 5. These findings of significant, community-level habitat limitation provide insight into how global declines in structurally complex estuarine habitats may have reduced the fishery production of coastal ecosystems.

1. 量化移动消费者（mobile consumers）对生境可利用性（habitat availability）变化的响应，对于明确种群水平生产力在多大程度上受生境限制，而非受其他潜在密度非依赖因子调控，具有至关重要的意义。
2. 在景观尺度（landscape scales）下，可通过监测生境可利用性变化时种群密度与觅食行为的改变来探究该问题。随着生境可利用性提升，种群密度可能出现三种变化情形：(1) 下降（单位面积生产力降低，生境限制作用较弱）；(2) 保持稳定（单位面积生产力不变，存在生境限制）；或(3) 上升（单位面积生产力提升，生境限制作用较强）。
3. 本研究通过对比邻近或不邻近其他人工礁（artificial reefs）与周边自然礁（natural reefs）的人工礁上的种群密度与摄食率，在原位开展了为期五个月的实验，以探究移动性河口消费者对生境可利用性变化的响应。
4. 通过构建人工礁或利用自然礁来操纵生境可利用性，我们发现，随着生境面积增加，幼年石蟹（juvenile stone crabs）的种群密度下降至原来的三分之一（即生境限制作用较弱）。然而，成年石蟹的种群密度在各处理组间均保持稳定，表明生境限制是该物种后期生活史中的瓶颈环节。豹蟾鱼（oyster toadfish）的种群密度也未随生境可利用性提升而发生变化（即存在生境限制），但其他隐蔽性鱼类（cryptic fishes）的种群密度则随生境可利用性提升而下降（即生境限制作用较弱）。摄食与丰度数据显示，部分移动性鱼类在本次生境操纵实验中存在生境限制现象，其中个别案例甚至可能表现出较强的生境限制作用。
5. 这些关于群落水平生境限制的重要发现，有助于我们理解全球范围内结构复杂的河口生境（structurally complex estuarine habitats）衰退，可能如何降低了海岸生态系统的渔业生产力（fishery production）。