FISIIKKV HILLKTIN: VOL. 8(;. NO. 4 



Figure \.— Sebast.es mystinus next to canopy of bull kelp, Nereocystis leutkeana, off Mendocino. 



In this paper we consider how the trophic rela- 

 tions of 5. mystinus respond as seaward and shore- 

 ward movements of the surface water produce 

 alternating episodes of upwelling and downwelling. 

 Emphasis is on how the resulting environmental 

 changes alter the relative availability of food. 

 Among studies of marine fishes, this is, to our 

 knowledge, the most comprehensive attempt yet 

 made to integrate data on food, potential food, and 

 environmental variables— all key elements in trophic 

 relations. 



METHODS 



The study lasted from the winter of 1976-77 to 

 the summer of 1981, with the first 15 months in- 

 volving exploratory work along about 15 km of the 

 Mendocino coast south of Point Cabrillo. A study 

 site was then established off Salmon Point (Fig. 2) 



during the spring of 1978, and from that time sam- 

 pling followed a set regime. 



Study Site 



The study site (Fig. 3) was in 10-15 m of water, 

 about 300 m from shore. Rocks the size of houses 

 jutted 10-15 m above the water at the seaward 

 perimeter of the site, but despite the shelter offered 

 by these rocks, most of the area was regularly swept 

 by wind and sea. Except for isolated pockets of sand, 

 the site was floored by rock pavement and boulders 

 (some 5-15 m in diameter), largely swept clean by 

 the turbulence and surge that prevailed most of the 

 time. 



Environmental Variables 



During each sampling session, we noted the gen- 



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