In the spring of 2003, California Department of Fish and Game (CDFG) personnel began quarterly sampling of Salton Sea fish at fourteen stations around the sea, as the basis of a long term monitoring program. In conjunction with this effort, water quality sampling takes place at the same time and place. *Note: This dataset should be viewed with the 'Quarterly Fishery Surveys - Salton Sea [ds428]' dataset. Methods: Eleven sampling sites comprise three broad habitat types: pelagic (3 sites), near-shore (8 sites), and estuarine (3 sites). The pelagic sites are in the approximate middles of the north basin, south basin and inter-basin areas of the Sea. The near-shore sites are spaced widely apart, four each, near the west and east shores, to capture as much breadth of habitat as possible. The estuarine sites are in the body of the Sea, close enough to the mouths of the New, Alamo, and Whitewater Rivers, to be under the influence of their outflows. The three deep water (pelagic) sites were completely unproductive for gill net sampling of fish during the first year of sampling. They have subsequently been dropped from the sampling protocol. Sampling takes place during each of the putative seasons, as follows: spring- April and May; summer- July and August; fall- October and November; winter- January and February. We attempt to compress the total sampling period into as few days as possible, to the extent that the weather, equipment maintenance, and personnel scheduling constraints allow. Nets are set for a 24 hour period. At the time of each set and retrieval of nets, water temperature, conductivity, specific conductivity, dissolved oxygen and sampling depth are measured and recorded, at the approximate mid-net water depth. Measurements are made with a handheld YSI meter, Model 85. Salinity is calculated from the specific conductivity measurement using the following algorithm: Salinity = 0.013(SC2) - 0.233(SC) + 17.102