Does method of field preparation affect survival and growth of juvenile Chinook salmon in agricultural floodplains?
There is growing interest to integrate conservation initiatives into agricultural practices using a reconciliation ecology framework. In Californias Central Valley, one approach to improving crucial nursery habitat for threatened and endangered fish species is by re-creating floodplain habitats through the inundation of agricultural fields during the non-growing season. We conducted a series of field experiments in agricultural floodplains (winter-flooded rice fields that were once natural floodplains) to explore whether different field preparation methods enhanced growth and survival of floodplain-dependent fish species. Approximately 8,000 juvenile fall-run Chinook Salmon (Oncorhynchus tshawytscha) were reared for at least 28 days on eight, 0.2 ha experimental fields. Each experimental field represented one of four treatments (two replicates per treatment): addition of large wood, addition of in-field canals, addition of both large wood and in-field canals, and control-where no additional field preparations were implemented beyond standard post-growing practices: i.e., chopping rice into stubble, baling and removing excess rice straw, and discing the field with a single pass by plowing rice straw into the ground to promote decomposition. We found no significant difference in water temperature, fish growth or fish survival among habitat treatments. Across treatments, survival ranged from 50.1%-78.3% and averaged 65.75% (/- 7.89% SE). These findings suggest agricultural floodplains require no additional modifications to promote fish growth and survival. Results illustrate the benefits of integrating working landscapes with conservation initiatives by creating more accessible and beneficial habitat for native fishes.