HOBSON and CHESS: TROPHIC RELATIONS OF THE BLUE ROCKFISH 



Figure 8.—Velella velella being driven shoreward by a northwest wind off the coast of northern California. 



major effects of storms on the nearshore habitats 

 came from 1) physical force of waves and surge, 

 and 2) suspended sediments carried by coastal 

 runoff into the nearshore habitats after heavy rains. 

 The first of these was the more apparent, at least 

 in exposed locations where often many of the ben- 

 thic algae and sessile invertebrates were swept 

 away. This force, intensified when the water car- 

 ried abrasive sediments, swept away most of the 

 Nereocystis, although some plants survived the 

 winter in sheltered places where they continued to 

 produce sori. Suspended sediments had their most 

 obvious effects in locations sheltered from water 

 movement, where they frequently settled to blanket 

 the benthos. Probably a more profound effect of 

 materials in suspension, however, was reduced 

 transparency of the water that limited the amount 

 of light (already at low levels owing to the shorter 



days and low sun angle) reaching phototrophic 

 organisms. 



As a general result of these, and probably other 

 forces in combination, the nearshore habitat ap- 

 peared relatively barren during the latter stages of 

 the downwelling season. That storms were a major 

 factor in reducing the vitality of this habitat was ap- 

 parent during the relatively mild winter of 1978-79, 

 when the effects described above were reduced. 

 That was the only year, for example, when mysids 

 were noted to be conspicuous in the nearshore 

 habitat throughout the winter. 



Feeding Conditions 



The diet of S. mystinus relative to foods available 

 during the downwelling season was assessed dur- 

 ing 10 days of sampling under downwelling condi- 



729 



