Fish assemblage at a newly restored tidal wetland reflects surrounding waterways in the Sacramento‐San Joaquin Delta

Introduction We studied the response of fish assemblages, water quality, and plankton following the completion of 700 acres of a 1184‐acre tidal restoration project (Dutch Slough Tidal Restoration; DSTR) in a system degraded by water diversions, channelization, non‐native species, and wetland loss. Objectives We assessed whether specific design features at DSTR supported different fish assemblages and environmental conditions as compared to each other and as compared to non‐restored mainstem reference sites. Methods We sampled water quality, chlorophyll ɑ, zooplankton, submersed aquatic vegetation (SAV), and nearshore fish assemblages within different habitats at DSTR. We compared these variables between DSTR and reference sites and between different habitats at DSTR. Results Our non‐metric multidimensional scaling analysis showed high community similarity between DSTR and reference sites. Despite the overall similarity, an Indicator Species Analysis showed that reference sites had significant associations with more native species than DSTR, and within DSTR there were fish guild differences between the two slough designs and the open water borrow pit. Open‐water habitat at DSTR yielded higher turbidity, chlorophyll ɑ, zooplankton, and daytime dissolved oxygen concentrations than sloughs. SAV was abundant in the terminal slough and the inundated borrow pit but was minimal in the non‐terminal slough. Conclusions References had more native species than DSTR , suggesting that increasing connectivity to main waterways may facilitate native fish presence, and design features in the restoration influenced fish community and environmental conditions.