The objective of this study was to assess the relative distributions of non-native resident fishes occurring in littoral habitats during the drought year of 2014 within the western and northern portion of California's Sacramento-San Joaquin Delta (Delta), USA. A number of non-native resident fish species (e.g., black bass, Micropterus spp.) in the Delta have undergone remarkable increases in density in the early 2000s and they are potential predators of endangered native fishes such as Chinook Salmon (Oncorhynchus tshawytscha) and Delta Smelt (Hypomesus transpacificus). The Delta makes up the tidal freshwater portion of the San Francisco Estuary in California; however, the critically dry year of 2014 caused a considerable intrusion of salinity field within this region and may have caused a shift in the resident fish community. To evaluate the response of non-native resident fishes to this salinity intrusion, a boat electrofishing survey was conducted in November of 2014 in the western and northern part of the Delta by the United States Fish and Wildlife Service, Lodi, California Office as part of the Interagency Ecological Program for the San Francisco Estuary. Replicate sampling was done for each site in this study in order to account for false zeroes through the estimation of capture probability.
