Timing of hydrologic anomalies direct impacts on migration traits in a flood pulse fishery system. Issue 3 (26th January 2023)

• Record Type: Journal Article
• Authors: Deng, Qi; Sabo, John L.; Holtgrieve, Gordon W.; Ngor, Peng Bun; Holway, Joseph
• Is Part Of: Journal of applied ecology. Volume 60:Issue 3(2023)
• Page Start: 494
• Page End: 506
• Publication Date: 2023-01-26
• Subjects: environmental flow -- fish migration -- food security -- hydrologic variation -- MARSS -- reservoir management -- spectral analysis; Agriculture -- Periodicals; Biology, Economic -- Periodicals; Agricultural ecology -- Periodicals; Applied ecology -- Periodicals; 577
• DOI: 10.1111/1365-2664.14349
• Languages: English
• ISSNs: 0021-8901

Abstract

Abstract: Understanding adaptive reservoir management strategies that balance ecological outcomes with other objectives necessitates properly articulated environmental objectives. Aside from flood pulse extent related metrics, residual‐based descriptors provide robust descriptions of fish assemblage structure and harvest. We proposed a model framework based on spectral analysis of hydrologic variation and the Multivariate AutoRegressive State Space (MARSS) model to statistically quantify the effect sizes of hydrologic variation impacts on total fish catch and functional group (migration types) fish harvest and applied it to 17 years of fish harvest data from the Lower Mekong River Basin (LMB). Our findings suggest that duration and timing of hydrologic anomalies matter as much as their magnitude. Anomaly droughts coupled with strong pulse can benefit species if timed correctly. Longitudinal migrators were more sensitive to anomalous floods and droughts than other migratory species. Fish catch projections using effect sizes derived from historical data revealed that a well‐timed and protracted drought followed by a powerful flood pulse would be advantageous to the fishery, but a flood delay could negate such benefits. Synthesis and applications : We designed a spectral analysis framework to quantify hydrological variation and linked it with fishery harvest records. Quantified effect sizes of hydrologic anomalous events demonstrated one designed hydrograph for fishery benefits: properly timed prolong drought followed by a strong flood pulse. Our results add to a growing body of research that suggests ecological flows can be engineered. For most dams, the rule curve describing reservoir releases and resulting downstream hydrograph are designed in an ecological vacuum in which the objectives are to maximize human services—power production, flood control or navigation. Our work demonstrates that hydrograph can be designed to manage aspects of functional biodiversity directly. Though the exact shape of our hydrograph may not apply to other engineered river systems, we suggest that the approach can be applied generally, and globally both to developed and developing river basins. Specifically, a functional biodiversity rule curve could be optimized as an additional objective function in a multi‐objective optimization framework. Our methodology provides a quantitative method for deriving an ecological flow for this larger tradeoff analysis. Abstract : We designed a spectral analysis framework to quantify hydrological variation and linked it with fishery harvest records. Quantified effect sizes of hydrologic anomalous events demonstrated one designed hydrograph for fishery benefits: properly timed prolong drought followed by a strong flood pulse. Our results add to a growing body of research that suggests ecological flows can be engineered. For most dams, the rule curve describing reservoir releases and resulting downstream hydrograph are designed in an ecological vacuum in which the objectives are to maximize human services—power production, flood control or navigation. Our work demonstrates that hydrograph can be designed to manage aspects of functional biodiversity directly. Though the exact shape of our hydrograph may not apply to other engineered river systems, we suggest that the approach can be applied generally, and globally both to developed and developing river basins. Specifically, a functional biodiversity rule curve could be optimized as an additional objective function in a multi‐objective optimization framework. Our methodology provides a quantitative method for deriving an ecological flow for this larger tradeoff analysis. 概括: 要理解平衡生态影响和其他目标的适应性水库管理战略，就必须清晰定量环境需求。除了与洪水脉冲程度相关的度量之外，基于残差的指标还提供了鱼类群聚结构和渔业捕获的可靠描述。 我们提出一个基于水文变化的频域分析和多变量自回归时空模型的分析框架以统计量化水文序列变化对总体渔业捕获和不同功能特征(迁移策略)的鱼类捕获的影响， 并以湄公河‐洞里萨湖17年的渔业产量数据为例展示了该分析框架的应用。 我们的主要发现首先是水文序列中的异常事件的持续时间、发生时机和异常值量级同样重要。合适时机出现的异常枯水期和随之而来的强洪水脉冲的组合有益于渔业产量。其次是纵向迁移的鱼类对于异常洪水和枯水更为敏感。最后，在由历史数据分析得到的水文异常事件的量化影响的基础上，我们外推不同的水文序列对于未来渔业产量的影响并发现尽管上述水文序列的组合是有益于渔业产量，但是推迟到来的洪水会抹除这种正面影响。 总结和应用:我们设计了一个水文序列的频域分析框架以定量描述水文变化并同渔业产量联系起来。量化后的水文异常事件的影响显示存在一种可能益于渔业的流量过程:合适时机出现的异常枯水期和随之而来的强洪水脉冲的组合。 我们的工作为一个日益壮大的研究课题:设计满足环境需求的流量过程， 提供了补充。对于多数水库而言，在水库的调度曲线和相应的下游流量过程的设计中，主要以水力发电，防洪，和航运及其他人类社会运转需求为主要目标，生态环境常常空缺。我们的结果表明直接调节流量过程来实现生物功能多样性的可能。虽然设计的具体流量过程可能不适用于其他流域，但是我们认为这种分析框架可以被广泛应用至众多发达和发展中国家的流域。尤其是在考虑生物功能多样性的调度目标可以纳入一个多目标的调度优化任务中，我们的分析框架提供了一中量化的方法来设计这样多目标权衡过程中的生态流量。