This dataset supports efforts to estimate the abundance and trends in population size of Alaska harbor seals. Annual surveys of harbor seal populations are fundamental to estimation of seal abundance, distribution, and trends, which in turn are essential for stock assessment, conservation, and management. The most feasible approach to determining harbor seal distribution and abundance is to use aircraft to count seals when they haul out of the water and are visible. Harbor seals in Alaska occupy a geographically extensive range from approximately long. 172ºE to 130ºW (over 3,500 km east to west) and from lat. 51ºN to 61.5ºN (over 1,000 km north to south). Estimation of the abundance of harbor seals statewide requires broad-scale aerial surveys and these surveys have been conducted by NOAA Fisheries, the Alaska Department of Fish and Game, and other collaborators since the early 1980s. This dataset reflects counts of harbor seals from surveys conducted in Alaska between 1998 and 2002.

During this period, the range of Alaska harbor seals was divided into five survey regions and only one region was surveyed each year. This approach allowed observers to survey the entire coastline of each region, sometimes twice per year, to identify new harbor seal haul-out sites, and for individual haul-out sites to be surveyed multiple times in a given year, weather permitting. This intensive effort produced a lot of data for each region in a given year, but surveying the entire range to produce state-wide abundance and trend estimates required a period of 5 years.