The National Marine Mammal Laboratories' California Current Ecosystem Program (AFSC/NOAA) initiated a long-term marking program of northern fur seals (Callorhinus ursinus) at San Miguel Island, California in 1975. A sample of up to 300 pups has been tagged in the foreflippers with various types and colors of tags each year between 1975 and the present. Resighting surveys for marked animals are conducted annually at summer breeding sites. Resightings are also obtained from the public when animals are observed on beaches or in fisheries. The data are used in mark-recapture models to estimate the age and sex specific vital parameters of the population and to describe age and sex specific reproductive behavior and seasonal movements of animals throughout their lives.

The National Marine Mammal Laboratories' California Current Ecosystem Program (AFSC/NOAA) initiated and maintains census programs for California sea lions (Zalophus californianus) and northern fur seals (Callorhinus ursinus) at San Miguel and San Nicolas Islands, California. The program documents annual pup births, pup mortality, and temporal patterns in adult and juvenile presence at San Miguel Island. For both species, the database contains field data on the annual number of live pups and dead pups by location. At San Miguel Island, daily counts of adults, pups, and juveniles in a sample area are also available. The data are used to describe population trends and changes in land resource use among the species.

In May of 2001, the California Department of Fish and Game (CDFG) conducted an aerial photographic survey of the California coast and the offshore Channel Islands to obtain a minimum estimate of the population of harbor seals (Phoca vitulina richardsi) living in California. The developed photographs were examined to count the number of harbor seals present and determine the location of each haul-out site by comparison to photos taken in previous surveys. This survey was successful in obtaining nearly complete coverage of all known haul-out areas. The 1995 survey was the last complete coverage. The total county for 2001 is 12,312 harbor seals. This result is the lowest ever recorded by CDFG for a combined count of the mainland and all offshore islands. The California Department of Fish and Game (CDFG) conducted two surveys in 2002 in an attempt to provide better coverage and to lessen the chances of weather related problems. A total of 16 days were scheduled for aerial surveys from May 19 to July 19, 2002. Total count for Survey 1 was 10,541 harbor seals, while that for Survey 2 was 8,374 harbor seals. Camera problems that produced un-readable film and poor weather conditions prevented a complete assessment by either survey. The lack of complete coverage by either Survey 1 or 2 limited the total number of harbor seals counted. This is especially true in areas where past surveys revealed high concentrations of seals such as the northern Channel Islands and Point Reyes - Sonoma County coast. The California Department of Fish and Game (CDFG) conducted two aerial surveys in 2003 in an attempt to provide better coverage and to lessen the chances of weather related problems. A total of 20 days were scheduled for aerial surveys from May 25 to July 20, 2003. Complete coverage was achieved in both surveys. This was the first time CDFG conducted these surveys using a digital imaging camera. Total count for Survey 1 was 17,415, while that for Survey 2 was 17,778 harbor seals.