FISHERY BULLETIN: VOL. 69. NO. 3 



of the total, were seen being preyed on by this 

 sea star at the four study areas (Table 1) . The 

 diet of P. giganteus is remarkably variable or 

 generalized over the four subtidal observation 

 areas, but within each habitat the diet is more 



Table 1. — A list of prey species eaten by Pisaster gigan- 

 teus and Kelletia kelletii from January 1968 to July 1970. 



Prey 



(Closs) 



Pilaster giganteus 



Kdlctia kelUtii 



+ (S)i 



+ 



+ 



+ (S) 

 + (S) 



+ 



+ 



+ (S) 

 + (S) 



+ 

 + ts) 



^ (S) = Scavenge. 



selective or restricted (Figure 2). Variations 

 in the diet of P. giganteiis with each habitat 

 or microhabitat are attributed to the availability 

 and abundance of prey organisms, and prefer- 

 ences in the feeding behavior of the sea stars 

 in these four locations. 



Predator success may, in many instances, be 

 dependent upon the predator's ability to feed 

 upon what is available in a given habitat. The 

 prey must be abundant enough to be utilized as 

 a food source and the predator must be capable 

 of selecting these forms. Variability in diet 



120 



I lO- 

 100- 



90 



30 



n B  1 



,^^-^^'^^^'^^^^^^'' 



5TP' 



ON^ 



PREY 



Figure 2. — Comparison of the feeding behavior of 

 Pisastei- giganteus as observed in the four study sites 

 from August 1969 to July 1970. 



with changes in sea star habitat has been dis- 

 cussed by Mauzey et al. (1968). Feder (1959) 

 suggested that differences in the diet of the 

 sea star P. ochraceus can largely be attributed 

 to changes in prey availability. 



Evidence for opportunistic or adaptable pre- 

 dation by P. giganteus is drawn from variability 

 in diet within each habitat and a temporary 

 alteration in the feeding behavior of the Quast 

 Rock sea star population. On February 20, 1970, 

 12 out of 43 P. giganteus observed on or around 

 Quast Rock were found to be feeding. Six of 

 these individuals were eating Chama pellucida; 

 two, Balanus tintinnahulum; two, Se7'pulorbis 

 squamigems; and one, Pyura haustor. Altera- 

 tion in feeding was observed with the sudden 

 appearance of a potential food source during the 

 spring of 1970. Thousands of spawning squid, 

 Loligo opalescens, were observed in the proxim- 

 ity of Quast Rock on March 12, 1970. Spawning 

 had been reported to occur each year in the La 

 Jolla area (Fields, 1965), although "spent" in- 

 dividuals had not been sighted in the Quast Rock 

 location during the previous 12 months. Num- 

 bers of dying or dead squid were lying along the 

 bottom off Quast Rock. A total of 52 P. gigant- 

 eus was examined around Quast Rock ; of these, 



672 



