Assessment and Recovery of Stream Restoration Efforts on Fish Communities

Aquatic systems are subjected to disturbances of various types, including natural and anthropogenic, or can deteriorate due to accumulating unfavorable conditions, including receding banks, decreasing riparian vegetation, and disrupted flow patterns. An analysis was done on a variety of streams in central Illinois that experienced one or multiple anthropogenic disturbances without remediation to determine the natural recovery dynamics of each system. A separate analysis was performed on a multi-site restored stream with a complex restoration project with a variety of restoration methods. This data were collected over at periods of time spanning from 5-15 years, including time prior to disturbance/restoration and post-disturbance/restoration. Each study included a control site in which to compare disturbed or restored sites. Data collection included fish composition, fish density (catch per unit effort), and index of biotic quality (IBI). Analyses included NMS ordination and Euclidean distances. I found that the more disturbances a system experiences, the less it recovers to its original composition and potentially shifts to a new community. Large shifts were experienced in community metrics immediately after the disturbance. Additionally, after about 36 months or sooner post-disturbance, most streams returned to or close to pre-disturbance conditions in regards to species richness, fish density, and IBI. Additionally, there appeared to be a level of relative stasis after about 36 months post-disturbance. In systems with two or fewer disturbances, community metrics surprisingly improved past pre-disturbance conditions. In the restored sites, there appeared to be large amounts of variation between sites and treatment methods, making definitive conclusions difficult to attain. All restoration sites displayed large-scale changes in species abundance, both increases and decreases, and variable colonizations and extinctions as a result of restoration. Control sites for restoration assessment exhibited minimal shifts in composition during pre-restoration sampling. However, composition following restoration varied dramatically between all sampling events with large compositional shifts occurring through the last sampling event. The large amount of variation in data suggest that this restoration was only moderately effective, at least to date. In conclusion, disturbed sites should be monitored for at least three years to fully understand its recovery dynamics and to determine whether active restoration efforts are warranted. Sites that do not recover during this time frame will likely require direct intervention to achieve recovery. Collectively, such information will help fisheries managers to better predict whether a proposed restoration project will be successful based on previous data