FISHERY BULLETIN: VOL. 86, NO. 4 



Figure 11.— Siphonophores off Mendocino. The physonect Stephanomia bijuga (left), and the calycophore Praya dubia (right). 



indicator = 1 cm. 



Scale 



tions, but because fall and winter were so different, 

 we consider them separately. We did not observe 

 upwelling conditions during this period. 



The major foods during six days of fall downwell- 

 ing, based on the ranking indices (Table 4), were 

 pelagic hydrozoans, specifically siphonophores, but 

 vegetation comprised a larger part of the total diet 

 volume. Virtually all plant materials taken at these 

 times, however, were sori of A'', leutkeana. As was 

 true during the upwelling season, there tended to 

 be more vegetation in the diet when there were 

 fewer of the larger gelatinous zooplankters in the 

 water column. For example, during the sampling 

 session of 18 October 1978 (Table 1), when the sur- 

 face plankton-collections took 400 siphonophores 

 and ctenophores, only 1 of the 9 fish collected had 

 consumed plant material (one sorus ofN. leutkeana). 

 On the other hand, during the sampling session of 



16 October 1979 (Table 1), when the surface plank- 

 ton-collection took only 30 siphonophores and cteno- 

 phores, 10 of 13 fish collected had consumed vege- 

 tation (x diet volume = 80%, virtually all of it 

 sori of A^. leutkeana; number taken = 1-21, x = 

 9.0), and two others were empty. 



Our assessment of the diet and concurrent com- 

 position of the plankton during winter downwelling 

 is limited to four days of sampling (Table 5). Data 

 from these collections are combined for consistency 



Figure 12.— Pelagic gastropods off Mendocino. The heteropod 

 Caranaria japonica (upper), and the pteropod Corolla spectabilix 

 (lower). Scale indicator = 1 cm. Often in areas where blue rockfish 

 are feeding many of the C. spectabilis present have lost the bulbous 

 central part of their body (pseudoconch and viscera). 



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