Food habits of harbor seals (Phoca vitulina richardii) in San Francisco Bay, California

Abstract

The diet of harbor seals (Phoca vitulina richardii) in San Francisco Bay (SFB) in California was examined from July 2007 to July 2008 via scat analysis. Scats were collected from five major haul-out sites; 22 species of fish and one species of crustacean were identified from 422 scats. The reliance of a non-native invasive species, Yellowfin Goby (Acanthogobius flavimanus), increased in importance in the diet. Additionally, another non-native invasive fish species, Chameleon Goby (Tridentiger trigonocephalus), was found for the first time in the diet of harbor seals in SFB. Harbor seal diet was compared between seasons, locations, and years using Spearman's rank correlations; diet was statistically different between years (1991-1992 and 2007-2008), between the pupping and non-pupping seasons, and between North SFB and South SFB haul-out locations. California Department of Fish and Game (CDFG) trawl data were also compared to harbor seal diet data and were found to be significantly correlated.