Seasonal abundance of pinnipeds at San Nicolas Island, California, 1980-1982 by Brent S. Stewart and Pamela K. Yochem. Bull. Southern California Acad. Sci., 83(3):121-132, 1984. Seasonal cycles in abundance of northern elephant seals, California sea lions, harbor seals, and Guadalupe fur seals at San Nicolas Island, California, were monitored by frequent ground and aerial surveys from February 1980 through September 1982. Northern elephant seals were most abundant in late January and early February during the height of their breeding season and again in late April to early May when juveniles and adult females hauled out to molt. Sea lions were most abundant in late June to early July during the height of their breeding season and were least abundant in winter and early spring. Harbor seals were in greatest abundance in late May to early June when they were molting and numbers were lowest in winter. Guadalupe fur seals were present from June through September during their breeding season. Seasonal populations and pup production of elephant seals, sea lions, and .harbor seals increased each year.