Disruption of natural disturbance regime decouples habitat and life stage in a keystone species

IF 2.7 3区 环境科学与生态学 Q2 ECOLOGY
Ecosphere Pub Date : 2024-10-14 DOI:10.1002/ecs2.70017
Joseph E. Merz, Rocko A. Brown, Kirsten Sellheim, Steven C. Zeug
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引用次数: 0

Abstract

Anthropogenic disturbance of stream ecosystems, often chronic in nature, has been studied extensively. However, when disturbance is driven by more than one resource policy over many decades, feedback between habitat evolution and biological adaptation can be disrupted and ecological function affected in unforeseen ways. We analyzed over 100 years of Chinook salmon (Oncorhynchus tshawytscha) length frequency trends associated with fisheries management and changes in available spawning substrate (habitat) linked to flow regulation in a highly altered California river. Over time, salmon lengths generally decreased, fluctuating with exploitation (ocean harvest) and hatchery production rates. Female size reduction, coupled with a degrading and coarsening channel, and perching peripheral habitat related to past mining activity, indicates available spawning substrate may be too large to support the current salmon population. Assuming a salmon can move material ~10% of her body length, length frequency data and current substrate size distribution suggest that increasing salmon sizes to historic distributions could increase available spawning habitat by as much as 13%. Alternatively, decreasing spawning substrate size could support a greater portion of the current population. To test the latter hypothesis and inform future management actions, we monitored two spawning riffles where large and small gravel was placed on top of a cobble. We observed an immediate spawning activity increase that was more pronounced where smaller gravel was deposited. Following a decade of habitat decline, the two sites were both replenished with medium gravel. Elevated spawning use occurred immediately at both sites, commensurate with this intermediate size, further supporting our hypotheses. Sediment coarsening and habitat disconnect below dams, combined with reduced salmon size, indicate the natural spawning process may be decoupled from available habitat below dams in the foreseeable future without continuous intervention. Actively managing salmon population demographics through modified hatchery and size-selective harvest practices and developing a coarse sediment budget with size-appropriate material for regulated anadromous rivers could produce immediate benefits for ecosystem services, including salmon populations. However, these management actions will require continued maintenance and informed socio-ecological goals to remain successful.

Abstract Image

自然干扰机制的破坏使一种关键物种的栖息地和生命阶段脱钩
人类活动对溪流生态系统的干扰往往是长期性的,对此我们已经进行了广泛的研究。然而,当几十年来不止一项资源政策造成干扰时,栖息地进化和生物适应之间的反馈就会被破坏,生态功能也会受到不可预见的影响。我们分析了 100 多年来大鳞大麻哈鱼(Oncorhynchus tshawytscha)的长度频率趋势,这些趋势与渔业管理以及在一条高度变化的加利福尼亚河流中与流量调节相关的可用产卵基质(栖息地)的变化有关。随着时间的推移,鲑鱼的体长普遍下降,并随着开发(海洋捕捞)和孵化生产率的变化而波动。雌性体型的减小,加上河道的退化和变粗,以及与过去采矿活动有关的周边栖息地,表明可用的产卵基质可能太大,无法支持当前的鲑鱼数量。假设大马哈鱼可移动的材料约为其体长的 10%,长度频率数据和当前的底质大小分布表明,将大马哈鱼的大小增加到历史分布水平可将可用产卵栖息地增加多达 13%。或者,减小产卵基质的大小也可以支持当前种群的更大一部分。为了验证后一种假设并为未来的管理行动提供信息,我们监测了两个产卵溪流,并在卵石上放置了大块和小块砾石。我们观察到产卵活动立即增加,在铺设较小砾石的地方更为明显。在栖息地减少十年之后,这两个地点都补充了中型砾石。这两个地点的产卵活动立即增加,与中等大小的砾石相称,进一步支持了我们的假设。大坝下沉积物变粗、栖息地断开,再加上鲑鱼体型减小,这表明在可预见的未来,如果不进行持续干预,自然产卵过程可能会与大坝下的可用栖息地脱钩。通过修改孵化和大小选择性捕捞方法来积极管理鲑鱼种群数量,并为受管制的溯河产卵河流制定大小适宜的粗沉积物预算,可为生态系统服务(包括鲑鱼种群)带来立竿见影的效益。然而,这些管理行动需要持续的维护和知情的社会生态目标才能保持成功。
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来源期刊
Ecosphere
Ecosphere ECOLOGY-
CiteScore
4.70
自引率
3.70%
发文量
378
审稿时长
15 weeks
期刊介绍: The scope of Ecosphere is as broad as the science of ecology itself. The journal welcomes submissions from all sub-disciplines of ecological science, as well as interdisciplinary studies relating to ecology. The journal''s goal is to provide a rapid-publication, online-only, open-access alternative to ESA''s other journals, while maintaining the rigorous standards of peer review for which ESA publications are renowned.
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