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

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 f..., Changes in female salmon size (1919–2021)
Length measurements of adult Chinook Salmon returning to the LAR have not been consistently recorded. However, LAR hatchery and natural production are managed as a single population. Therefore, we applied the correlation between Chinook Salmon fecundity and adult FL (Healey and Heard 1984) to 66 years of Nimbus Fish Hatchery fecundity data (Williams 2006; CDFW unpublished data) to estimate mean annual adult female Chinook Salmon body length in the LAR (1955 to 2021). In addition, Clark (1928) provided FL data from 1,423 Chinook Salmon caught by gill-net in the Sacramento River near the LAR mouth (1919–1921). Because sex was not provided for individual fish, we used the female-to-total population FL ratio from recent LAR fish surveys (CDFW unpublished data) and multiplied this by the estimated length frequencies from Clark (1928) to estimate average female size for that period, assuming that this relationship would remain constant over the period..., , # Data from: Disruption of natural disturbance regime decouples habitat and life stage in a keystone species

Below is a brief summary of dataset contents, contextualized in experimental procedures and results.

We linked various state and federal data sets related to salmon escapement, harvest, fish size, and habitat use in an Excel file to perform correlative analyses.

Four files are uploaded including Exploitation and salmon size (FL), salmon spawning use (number of redds observed), and calculations of the theoretical substrate particle size a female could move based on her size.

Chinook Salmon fecundity data were acquired from the Nimbus Fish Hatchery (California Department of Fish and Game. [https://wildlife.ca.gov/Fishing/Hatcheries/Nimbus](https://wildlife.ca.gov/Fishing/Hatcheries/Nimbus)

Salmon exploitation rate estimates were acquired from NOAA Fisheries: National Marine Fisheries Service (NMFS), 7600 Sand Point Way, NE, BIN C15700; Seattle, WA 98115-0700 [www.noaa.gov/fish...

人为干扰河流生态系统（通常具有长期性）已被广泛研究。然而，当干扰由数十年间的多种资源政策驱动时，栖息地演化与生物适应之间的反馈可能被破坏，生态功能会以不可预见的方式受到影响。我们分析了加州一条高度受干扰河流中，与渔业管理及产卵基质（栖息地）变化（与流量调控相关）相关的奇努克鲑鱼（Oncorhynchus tshawytscha）100多年的体长频率趋势。随着时间推移，鲑鱼体长总体呈下降趋势，随捕捞（海洋收获）和孵化场产量波动。雌性体型减小，加之河道退化与粗化，以及与过去采矿活动相关的边缘栖息地占据，表明可用产卵基质可能过大，无法支撑当前鲑鱼种群。假设鲑鱼可移动约自身长度10%的物质，体长f...

成年奇努克鲑鱼返回LAR的体长测量记录并不一致。然而，LAR孵化场和自然种群被作为单一群体管理。因此，我们将奇努克鲑鱼繁殖力与成年FL之间的相关性（Healey和Heard 1984）应用于Nimbus鱼类孵化场66年的繁殖力数据（Williams 2006；CDFW未发表数据），以估算1955至2021年LAR中年均成年雌性奇努克鲑鱼的体长。此外，Clark（1928）提供了1919–1921年间在萨克拉门托河LAR河口附近通过刺网捕获的1423条奇努克鲑鱼的FL数据。由于未提供个体鱼类的性别，我们使用近期LAR鱼类调查中雌性与总种群的FL比例（CDFW未发表数据），并将其乘以Clark（1928）的估算体长频率，假设该关系在此期间保持恒定，以估算该时期的平均雌性体型..., , # 数据来源：自然干扰机制的破坏使关键物种的栖息地与生活史阶段解耦

以下是数据集内容的简要摘要，结合实验流程与结果进行说明：

我们将与鲑鱼逃逸量、捕捞率、体型及栖息地利用相关的多个州和联邦数据集关联至Excel文件，以进行相关性分析。

上传的四个文件包括捕捞率与鲑鱼体型（FL）、鲑鱼产卵利用（观察到的产卵巢数量），以及基于雌性体型计算的理论基质颗粒大小。

奇努克鲑鱼繁殖力数据来源于Nimbus鱼类孵化场（加州鱼类和猎物部，[https://wildlife.ca.gov/Fishing/Hatcheries/Nimbus](https://wildlife.ca.gov/Fishing/Hatcheries/Nimbus)）。

鲑鱼捕捞率估算来源于美国国家海洋和大气管理局渔业局：国家海洋渔业服务处（NMFS），7600 Sand Point Way, NE, BIN C15700；西雅图，WA 98115-0700 [www.noaa.gov/fish...