Grigg et al.: Spatial and seasonal relationships between Phoca vitulina richardii and their prey 
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Spatial overlap of Pacific harbor seals ( Phoca vitulina richardii) and important harbor 
seal prey species in San Francisco Bay, CA, for four seasons, 2001-05. Density of seal 
locations is indicated by shading of the 1-km grid, with darker shading indicating 
more frequent use by seals. Relative abundance of specific harbor seal prey species 
(as noted in the map legends) caught at each fish sampling station is indicated by 
size of the circle marking station location, and larger circles indicate greater catch 
per unit of effort of prey at that location, in number of individuals per hectare (1 
hectare = 0.01 km 2 ). Fish species shown are representative of harbor seal prey spe- 
cies found to have the greatest correlation with seal location for that season: A) 
Spring — English sole ( Pleuronectes vetulus ), B) Summer — Pacific staghorn sculpin 
( Leptocottus armatus), C) Fall — plainfin midshipman ( Porichthys notatus ), and D) 
Winter — plainfin midshipman (P. notatus). 
At the 1-km scale, most correlations were positive 
(i.e., greater co-occurrence of harbor seal locations with 
greater prey CPUE), but not strong (correlation coef- 
ficients <0.6). The correlation coefficients for plainfin 
midshipman were greatest among most spatial scales 
during the fall and winter. The coefficients for English 
sole were greatest among most spatial scales during 
the spring and summer. The coefficients for Pacific 
staghorn sculpin were second greatest during summer 
and fall. 
