PinnipedOceanic is a polygon shapefile of the densities of two pinniped species - northern fur seal and California sea lion - observed off the northern/central California coast, during the Oceanic season (August 15 - November 14). These at-sea densities are the result of a synthesis of data from eight shipboard and aerial survey programs conducted in the study area in the years 1980-2001. Pinniped observation data and trackline data from these studies were converted to a common format. All aerial data were continuous; ship-based data were converted separately into a continuous transect to the extent possible. From the digitized survey data, the distributions of effort and of species were mapped into 10'x10' latitude x longitude cells using CDAS, a custom geographic information system for analyzing marine bird and mammal surveys (MMS-CDAS 2001). The length and width of the survey trackline in a given cell (estimated trackline width varied by platform, depending on speed and height above water) were used to estimate the area sampled. The number of pinnipeds of each species seen in a cell was then divided by the area sampled in the cell to estimate density. If a cell was censused more than once, densities were averaged, with adjustment made for effort.