Robichaud et al.: Selection of Chionoecetes opilio and Hyas spp by Gadus morhua and Raja radiata 



673 



Figure 5 



Percentage by weight of prey categories 

 against total weight of stomach contents 

 from cod sampled in September 1982. Dark 

 bar represents the percentage by weight of 

 total toad crabs (Hyas araneus, H. coarc- 

 tatus, unidentified Hyas). 



crab per cod stomach for samples 7 and 8 had increased 

 to 0.47 and 1.16, respectively (Table 1). The percent- 

 age by weight of toad crab in cod samples 7 and 8 was 

 5.7 and 18.1%, respectively. The mean number of toad 

 crab per cod stomach (0.37 and 1.16 crab/stomach, 

 respectively) was similar to the mean number of snow 

 crab found in the same cod stomach samples (0.47 and 

 1.16 crab/stomach, respectively) (Fig. 4; Table 1). In 

 samples 7 and 8, cod had concentrated their feeding 

 on other invertebrates (49.7 and 82%, respectively) 

 such as euphausiids, gastropods and polychaetes. 



During September 1982, in cod sample 9, taken by 

 Danish seiners on muddy or sandy bottom at inter- 

 mediate depths (66-90 m), the percentage by weight of 

 snow crab was 24.5%, and the mean number of snow 

 crab per stomach was 0.78 (Fig. 5; Table 1). The in- 

 crease in the percentage by weight of snow crab in 

 September is a consequence of a size increase of juve- 

 nile crab ingested in September (13.2g/crab) compared 

 with July (3.7g/crab). The percentage by weight of toad 

 crab in sample 9 was 16.1%, and the average number 

 of toad crab per cod stomach was 0.22 (Fig. 5; Table 

 1). The largest percentage of total weight in sample 

 9 was composed of fish (48.6%) such as mackerel 

 Scomber scombrus, pleuronectids, and smaller gadids. 



Sample 9 

 Danish Seine 



Cod 

 " 1 8 Cod 

 09/26/82 

 (6 6-90m) 



Sample 13 



Jig 

 _ 89 Cod 

 09/28/82 

 _ (46m) 



