Wageningen University & Research, Aquaculture and Fisheries group, Wageningen, the Netherlands.
Department of Animal Ecology and Physiology, Institute for Water and Wetland Research, Radboud University, Nijmegen, the Netherlands.
Sci Total Environ. 2021 Feb 10;755(Pt 1):142931. doi: 10.1016/j.scitotenv.2020.142931. Epub 2020 Oct 13.
The ecological efficacy of river restoration projects may change over time, resulting in the loss of their ecological function for targeted species. The goal of this study was to evaluate the rheophilic nursery function of restored floodplain channels over time, by analysing 30 years of monitoring data from 12 restoration projects in the lower river Rhine. We hypothesised that the nursery function would change over time, caused by the combined effects of decreasing flow conditions and succession processes affecting habitat heterogeneity. We found that nursery area suitability for rheophilic fish was almost 4 times higher in two-sided connected channels than in one-sided connected channels, although the response trends of rheophilic fish were similar for both water body types. These response curves showed clear optima with channel age, for rheophilic fish abundance at 13 to 14 years post-restoration, indicating optimal nursery conditions. On the other hand, rheophilic species richness showed a steadily decreasing trend with channel age, suggesting aging channels became less suitable as nursery areas for most rheophilic fish species. The presence of permanent flow was found to be the main driving factor in explaining both rheophilic fish community trends and habitat succession in individual restored channels. We did not observe an effect of habitat heterogeneity on nursery function for rheophilic fish. To create and maintain optimal nursery conditions in restored floodplain channels of strongly anthropogenically influenced rivers such as the river Rhine, we propose a management strategy involving cyclic rejuvenation through human intervention, focusing on restoring permanent flow, with a frequency of on average every 15 years, depending on the rate of aggradation and targeted rheophilic species. We also propose a thorough investigation of the relationship between habitat heterogeneity and nursery success in floodplain channels, as a next step in the identification of suitable nursery areas for rheophilic fishes.
河流修复项目的生态效果可能随时间而变化，从而导致针对目标物种的生态功能丧失。本研究的目的是通过分析莱茵河下游 12 个修复项目 30 年的监测数据，评估恢复后的漫滩河道的适栖性育幼功能随时间的变化。我们假设，由于水流条件的下降和影响生境异质性的演替过程的综合影响，育幼功能会随时间而变化。我们发现，与单侧连通河道相比，双侧连通河道的适栖性育幼区对洄游性鱼类更为适宜，尽管这两种水体类型的洄游性鱼类的响应趋势相似。这些响应曲线显示出与河道年龄明显的最佳值，表明在恢复后 13 至 14 年，洄游性鱼类的最佳育幼条件。另一方面，洄游性鱼类的丰富度随河道年龄呈持续下降趋势，表明随着时间的推移，老化的河道对大多数洄游性鱼类的适栖性降低。永久性水流的存在被发现是解释洄游性鱼类群落趋势和单个恢复河道生境演替的主要驱动因素。我们没有观察到生境异质性对洄游性鱼类育幼功能的影响。为了在像莱茵河这样受强烈人为影响的河流的恢复漫滩河道中创造和维持最佳的育幼条件，我们提出了一种管理策略，包括通过人工干预进行周期性的恢复，重点是恢复永久性水流，平均每 15 年进行一次，具体取决于淤积速度和目标洄游性鱼类。我们还建议进一步研究生境异质性与漫滩河道育幼成功之间的关系，作为确定洄游性鱼类适宜育幼区的下一步。
