FISHERY BULLETIN: VOL. 83, NO. 4 



Table 3.— Mean (+95% confidence interval) number of prey items and prey taxa per stomach 

 and total number of prey types for the seven species of juvenile rockfishes. 



Table 4.— Percent similarity (PSI) overlap values of juvenile rockfish diets. Proportions used for calculations are %IRI. 



serranoides melanops mystinus caurinus carnatus pinniger 



<45 mm <45 mm 



atrovirens 



caurinus 

 >45 mm 



carnatus 

 >45 mm 



Sebastes serranoides 



S. melanops 



S. mystinus 



S. caurinus (<45 mm) 



S. carnatus (<45 mm) 



S. pinniger 



S. atrovirens 



S. caurinus (>45 mm) 



S. carnatus (>45 mm) 



0.787 



important in their diet (Fig. 2). Thus, this spe- 

 cies' diet was similar to most other species 

 {Table 4). 



Sebastes pinniger had a very diverse diet (highest 

 number of overall prey taxa found; Ikble 3). In- 

 dividuals were found mainly over sand areas and the 

 sand/rock interface at the edge of the kelp forest, 

 generally within a few meters of the bottom. This 

 species' diet consisted mainly of copepods and zoea 

 larvae (open water prey), but gammarid amphipods 

 and mysid shrimp (substrate-associated prey) were 

 also important (Fig. 2). 



Figure 2 shows that these seven species can be 

 split into two basic categories: open water and 

 substrate-associated predators (this categorization 

 can also be seen in microhabitat differences [Carr 

 1983]). Open water predators— S. melanops, S. 

 mystinus, S. serranoides, and small S. caurinus and 

 S. carnatus— axQ those that ate mainly copepods and 

 zoea larvae. Substrate-oriented predators— S. 

 atrovirens and larger 5. caurinus and 5. carnatus— 

 are those that ate predominantly amphipods and 

 decapods. Sebastes pinniger is intermediate between 

 these categories. Its microhabitat and behavior are 

 that of a substrate-associated predator, but its 

 diet is more similar to the open water predators 

 (Tkble 4). 



Prey Distribution 



Midwater organisms such as copepods, zoea lar- 

 vae, and polychaetes were very abundant in all parts 

 of the water column. Calanoid copepods were the 

 most abundant type during the day at all depths, 

 while both calanoids and harpacticoids were very 

 abundant at night. Amphipods, mysids, caridean 

 shrimp, and isopods were very abundant in and 

 around all substrate types (kelp canopy, stipes, rocks, 

 and drift algae). Isopods and amphipods were most 

 abundant in the canopy and stipes, while amphipods, 

 mysids, and carideans were more often abundant 

 near rock and drift algae and around kelp holdfasts. 

 These invertebrates remained near substrate dur- 

 ing the day, moving farther away at night. 



Morphological Comparisons 



ANOVAs of relative head length, relative gill raker 

 length, and gill raker spacing among species were 

 all significant at the P < 0.001 level (Tkble 5). 

 Generally, the open water and substrate-associated 

 classifications also held true for groupings by 

 morphology. 



In general, open water predators had smaller 

 heads and larger gill rakers. Sebastes mystinus, S. 



536 



