Long and lasting: spatial patterns and temporal trends in a fish community responding to landscape-scale hydrological restoration of a coastal freshwater wetland complex

Context Freshwater wetlands, including those in coastal regions, are among the most important, albeit threatened, environments worldwide. Beyond protection, restoration is urgently required to halt the trend of wetland loss. Restoring natural hydrology offers potential to achieve this by landscape-scale rehabilitation of wetland habitat and connectivity for aquatic biodiversity, including freshwater fishes. Objectives This study assessed the response of a fish community, across pre-, during and post-restoration periods, to hydrological restoration works within an internationally significant coastal freshwater wetland complex with a history of flow diversion and drainage. Methods Biannual sampling of the fish community occurred across five zones of the wetland complex over the pre-, during and post-restoration periods spanning an eight-year timeframe (2012-19). Results The study revealed a coastal freshwater wetland harbouring an abundant (179,557 fish caught in this study) and regionally diverse (19 species) fish community, with the catch numerically dominated by native freshwater specialists and diadromous species. Fish community composition and abundance along with species diversity and total abundance responded significantly according to an interaction between zones and the three periods of restoration. Water quality and habitat parameters varied significantly in space and time over the study period, and helps to partially explain the responses of the fish community. Conclusions This study provides a practical demonstration on the application of landscape-scale restoration of wetland hydrology and associated rehabilitation of aquatic habitat and connectivity to benefit freshwater fishes.