Aquatic Mammals (1995)


From September 1984 to November 1985, sightings of 1594 groups of harbor porpoises (Phocoena phocoena) were made from a high vantage point at Pajaro Dunes, Monterey Bay, California, in a total of 761 hours of observations. Porpoises were seen within 300 m of the shore, mostly between 0700 and 1000 hr., apparently feeding nearshore. The number and size of porpoise groups sighted were greater in July, August and September than in other months of the year. Significantly more porpoise groups were present nearshore during flood tide than ebb tide. Variations in both the number and size of groups seen may have been related to food availability.

Nine stomachs of harbor porpoises collected in the Monterey Bay area from 1985 to 1986 were used for feeding habit analysis. Two families of
cephalopods and twelve families of fishes were found. Northern anchovy (Engraulis mordax) had the highest index of relative importance, spotted
cusk eel (Chilara taylori) was second, and rockfish (Sebastes spp.) was third, but market squid (Loligo opalescens) had the highest percentage
of frequency of occurrence. Harbor porpoises in Monterey Bay appear to change their diet seasonally.