Garcia-Rodriquez and Aurioles-Gamboa: Spatial and temporal variation in the diet of Zalophus californianus 



49 



San Pedro Martir (SPM) 



28° 24'- 



HA 



San Esteban (EST) 



112°40' 112=38' 1 12=36' 112=34' 112=32' 

 J L 



28=44- 



28=42' 



El Rasito (RAS) 



Angel de la Guarda 



28=49' 



Isla Granito (GRA) 



Isla Lobos (LOB) 



30=03'. 



Figure 2 



Location of sites where samples of California sea lion scats were collected at each island. 

 RA = reproductive area; HA = haulout area. 



the family name plus a sequential number. Otoliths from 

 prey species that were not identified to species, genus, or 

 family level were coded with "fish species" plus a number. 

 Three indices were used to describe the diet of sea lions. 

 Percent number (PN) represents the percentage of the 

 number of individuals for each prey taxon over the total 

 number of individuals found in all scat samples. Percent 

 of occurrence (PO) represents the percentage of scats hav- 

 ing a given prey taxon and indicates the percentage of the 

 population that is consuming a particular prey species. The 

 third index, index of importance (IIMP) incorporates PN 

 and PO and is defined as 



IIMP, 



'T ^ 



u 



X 



(1) 



where x t = number of individuals of taxon z' in scatj; 



X = total number of individuals from all taxa found 



in scat J; and 

 U = total number of samples with prey. 



The IIMP, developed for scat analysis (Garcfa-Rodriguez, 

 1999), was used to determine the importance of prey 

 species, their spatial and temporal variation in the diet. 



