Paralichthys oblongus. — Fourspot flounder were common in 

 the study area on all cruises (Table 1). Decapods were the most 

 important prey at all times of the year (Fig. 26, Table 10). Amphi- 

 pods were very important in winter and spring, but fishes appar- 

 ently replaced amphipods in the diet in fall and summer. This 

 seasonal shift from amphipods to fishes reflected the seasonal 

 abundance of small fishes in the study area and also seasonal differ- 

 ences in the size composition of the predator population. Fourspot 

 flounder captured in winter and spring were slightly smaller (.v 

 SL= 196 and 180 mm, respectively) than those taken in fall and 

 summer (.v SL = 214 and 221 mm. respectively) and fed more on 

 smaller prey items such as amphipods. Cephalo'pods were fre- 

 quently consumed in the fall. 



Amphipods were the most abundant food for smaller fourspot 

 flounder, although decapods contributed most to the volume of 

 food for all size classes (Fig. 27). Amphipods steadily decreased in 

 relative abundance in larger fishes, when decapods became the 

 most abundant food. Fishes, polychaetes, and cephalopods contrib- 

 uted more to the diet of larger P. oblongus. 



Mean prey number per stomach remained relatively constant for 

 all size classes of P. oblongus (Fig. 28). However, as larger fish 

 switched to larger prey items, mean total volume of stomach con- 

 tents increased. 



Overlap in Diet 



Overlap in diet varied seasonally with changes in species and size 

 composition of the predator community (Fig. 29). Merluccius bili- 

 nearis and U. chuss showed the greatest similarity in diet in fall 

 (Fig. 29A), when smaller individuals (,v SL= 127 and 51 mm. 

 respectively) dominated in the study area and fed mainly on small 

 planktonic crustaceans such as Parathemisto gaudichaudi and Cen- 

 tropages typicus. Stenotomus chrysops also fed heavih on these 

 two species and was classified with this group. Raja erinacea and 

 C. arctifrons, both of which fed heavih on Unciola irroraia. Byblis 

 scrniia, and Ampelisca vadorum, were grouped together. Paralich- 

 thys oblongus and U. regia were more similar to each other in their 

 diets than to other fishes in fall. Decapods and fish were the two 

 most important food taxa for these species in fall, and amphipods 

 were also important for both species. Lophius americanus. being 

 primarily piscivorous, had little similarity in diet to other species 

 but was classified with P. oblongus and U. regia which also ate 

 fish. 



In winter, predator groups changed for several reasons (Fig. 

 29B). First, S. chrysops was absent from the study area, and M. 

 americanus became common and was included in the classifica- 

 tion. Also larger U. chuss (.v SL = 250 mm) and M. bilinearis (.v 

 SL = 282 mm) were present. Unciola irroraia and Erichthonius 

 rubricornis were the most abundant food items for P. oblongus. M. 

 americanus. R. erinacea. C. arctifrons. and U. chuss. and all of 

 these species formed a group with high similarity. The one U. regia 

 captured had eaten fish and was classified with L. americanus. 

 Merluccius bilinearis. which fed mainly on hyperiids. copepods. 

 Dichelopandalus leptocerus. and chaetognaths. differed in its diet 

 from all other species. However, since M. bilinearis consumed 

 fish, it was joined to this latter group at a lower level of similarity. 

 The larger M. bilinearis present in the winter fed on different prey 

 than smaller M. bilinearis and cooccurring larger U. chuss. 

 Although M. bilinearis and U. chuss had similar diets in fall as 

 juveniles, their adult diets were quite dissimilar in winter, when 

 large I '. chuss ate more benthic pre> and M. bilinearis continued to 

 feed on planktonic species. Also in w inter. P. oblongus fed on more 



amphipods than decapods and fishes, and was grouped with other 

 amphipod feeders. 



In spring (Fig. 29C), as in winter, the corophiid amphipods U. 

 irrorata and E. rubricornis were the most important food for sev- 

 eral predators, and the classification was similar to winter, although 

 similarity values between predators were lower. Paralichthys 

 oblongus and R. erinacea fed heavily on U. irrorata, E. rubri- 

 cornis, and B. serrata and showed the highest similarity of any 

 predator pair. Urophycis chuss, C. arctifrons, and M. americanus 

 also fed heavily on U. irrorata and E. rubricornis. They were 

 included in this group, although they also fed heavily on other spe- 

 cies. Lophius americanus, U. regia. and M. bilinearis, though 

 somewhat dissimilar in diet, were more dissimilar to other preda- 

 tors and formed a separate group because all three species con- 

 sumed fishes. 



In summer, C. arctifrons and M. americanus displayed the great- 

 est similarity in diet, when C. arctifrons again fed heavily on 

 amphipods and E. rubricornis and U. irrorata were the most abun- 

 dant species consumed by both predators (Fig. 29D). Raja erinacea 

 and U. chuss again fed heavily on both these species during sum- 

 mer and were included in this group, but R. erinacea also fed heavi- 

 ly on ampeliscid amphipods. whereas U. chuss consumed many 

 Sagitta elegans and P. gaudichaudi . Parathemisto gaudichaudi 

 and D. leptocerus were the most abundant species consumed by M. 

 bilinearis and U. regia. both of which also fed on fishes. Paralich- 

 thys oblongus sw itched to a fish and decapod diet in summer and 

 was classified with L. americanus since both fed heavily on fish, 

 primarily M. bilinearis. Dichelopandalus leptocerus was con- 

 sumed by both species, so they were joined to M. bilinearis and U. 

 regia. 



A classification of predators from all seasons indicated two major 

 groups of similar feeders (Fig. 30). One group (Group I, Fig. 30) 

 fed main!) on benthic amphipods. primarily U. irrorata, E. rubri- 

 cornis. B. serrata. and A. vadorum. and brachyuran decapods (pri- 

 marily C. irroratus). A second major group (Group II, Fig. 30) fed 

 mainly on hyperiids, copepods. fishes, and caridean decapods (pri- 

 marily D. leptocerus). While some fishes consistently fed similarly 

 during all seasons (e.g.. R. erinacea). several predators belonged 

 to both groups, switching at various seasons. Thus U. chuss fed 

 mainly on hyperiids and copepods in the fall at which time it was 

 classified in Group II: during other seasons red hake were included 

 in Group I. Urophycis regia also fed differently in the fall from 

 other seasons and was classified in Group I in the fall. Paralichthys 

 oblongus fed preferentially on small fish in summer and fall, the 

 period of their greatest abundance, but fed more on amphipods in 

 winter and spring. 



Although the food habits of some species appeared to change sea- 

 sonally, this phenomenon may be attributed to seasonal changes in 

 size-class composition of the predators in the study area. The food 

 habits of most predators changed dramatically with size. Thus, diet 

 overlap between species could be greater than that between 

 different-sized fishes of the same species. To resolve such differ- 

 ences, each size class within a species was treated as an entity in the 

 normal classification for each season (Figs. 31-34). 



In fall, four major groups appeared in the classification (Fig. 31 ). 

 The first (Group I, Fig. 31) was composed of small-to-medium 

 skates, medium spotted hake, large fourspot flounder, small red 

 hake, and medium-to-large scup. These fishes fed mainly on cor- 

 ophiid and ampeliscid amphipods and caridean decapods. Group II 

 consisted mainly of piscivores, such as L. americanus and large M. 

 bilinearis. and other fishes w hich had prey in common. Group III 

 consisted of large fishes having C. irroratus as their most abundant 



