Pinniped assessment in the Point Reyes/Farallon Islands National Marine Sanctuary, 1982-83

Allen, Sarah; Huber, Harriet

From March 1982 to February 1983 we censused three species of pinnipeds [harbor seal, California sea lion, and northern (Steller) sea lion] found on the coast of the Point Reyes/Farallon Islands National Marine Sanctuary. We censused harbor seals semi-monthly and simultaneously at all traditional haul out sites. Seals were present throughout the year with most seals recorded in the breeding season; the maximum count for the season was 2502 with 566 pups. An enormous influx of animals occurred primarily at coastal locations during the breeding season and appeared to be from areas outside of the Sanctuary. The diurnal haul out pattern varied depending upon time of day, tide level, and physical features of the hauling ground. Disturbance also modified the seals’ diurnal pattern and was considered a factor in reproductive success. Preliminary recommendations for management are presented. California and northern sea lions were censused weekly during the breeding season (May—August) and semi—monthly during the rest of the year at Sea Lion Overlook, Point Reyes. We divided animals into five age—classes and compared coastal counts to counts on the Farallon Islands. Peak numbers were 338 at the Headlands in April and 3725 at the Farallones in January for California sea lions; for northern sea lions high counts were 19 at the Headlands in July and 192 at the Farallones also in July. No pups were observed at Point Reyes. Censuses were analyzed to clarify seasonal, diurnal and tidal fluctuations. Sea lions were censused in Tamales Bay during the herring run, December to March....Extensive report summarizing the results of a survey of harbor seals, California Sea lions and northern sea lions along the coast of Point Reyes. Looked at the numbers of each species present at different times of the year (different times in the breeding cycle). Includes tables of data and both tables and graphs which break down the population by sex and age.