FISHERY BULLETIN: VOL. 86, NO. 4 



10-20 m, which often limited visibility to a few 

 meters. These diatom blooms were most evident 

 during the intermittent episodes of downwelling. 

 The benthos similarly proliferated. Within a few 

 weeks after the initial upwelling, a growth of ben- 

 thic diatoms (primarily Isthmia nervosa and Tricer- 

 tium americana) appeared on the previously baron 

 rocks, and even on sand sheltered from wave surge. 

 Then larger elements of the biota began to increase 

 in size and number. Particularly evident were cal- 

 careous sponges (especially Leucosolenia spp.), 

 hydroids, and certain bryozoans. Benthic algae, 

 predominantly Desmarestia ligulata, rapidly over- 

 grew much of the rock substrata, while young A^ereo- 

 cystis leutkeana, which first appeared on the sea- 

 floor in May, had grown to the water's surface by 



mid-June. Swarms of mysids were increasingly 

 numerous near the seafloor in April (they had been 

 prominent for a month or more), and caprellid and 

 gammaridean amphipods on rocky substrata began 

 a sharp increase in numbers. 



The bull kelp had formed a dense canopy by mid- 

 July, and at about the same time large numbers of 

 sori (reproductive structures) began falling from the 

 kelp's fronds. (A frond that had recently lost a sorus 

 appears at the left side of Figure 1.) Planktonic 

 diatoms continued to proliferate during periodic 

 blooms, but by this time the benthic diatoms that 

 had carpeted much of the seafloor during the spring 

 were mostly gone. Similarly, the mysid swarms, 

 which had peaked in May and June, usually began 

 to decline by mid-July. Other elements of the biota, 



Table 2.— Food of adult Sebastes mystinus relative to near-surface planl<ton during upwelling episodes of the upwelling 



season, n = 7. 



722 



