LANGT0N: DIET OVERLAP BETWEEN SEVENTEEN NORTHWEST ATLANTIC PINKISH 



V V* C 



(5 CM LENGTH CLASSES) 



FIGURE 1.— Three dimensional plot of the diet overlap of Atlantic cod versus Atlantic cod; the same 

 data set. Presented here is an example of the graphics output from diet similarity calculations. The 

 peak represents 100% overlap for the same 5 cm length class of fish with a mirror image of values 

 on either side of the peak. 



shift in the diet of Atlantic cod from crustaceans 

 to fish. 



Atlantic Cod — Redfish 



Atlantic cod and redfish, Sebastes marinus 

 (Linnaeus), generally show low levels of diet 

 overlap (Fig. 2B). There were, however, some 

 medium overlap values occurring between the 

 smaller Atlantic cod and redfish. The peak value 

 of 49% occurred between redfish 16-20 cm (size 

 class 4) and Atlantic cod 6-10 cm (size class 2) 

 which was primarily the result of predation on 

 pandalid shrimp Dichelopandalus leptocerus. 

 Unfortunately, few of the redfish stomachs ex- 

 amined in this size class contained prey (2 out of 

 21 examined) so this peak may be artificially 



high, although in the other cases where medium 

 overlap levels were found, pandalid shrimp were 

 generally consumed by both predator species. 



Atlantic Cod — Longhorn Sculpin 



The pattern of diet overlap between Atlantic 

 cod and longhorn sculpin, Myoxocephalus octo- 

 decemspinosus (Mitchill), shows low to medium 

 overlap values over much of the size range of 

 both species. The values do decrease, however, 

 between the larger Atlantic cod (>61 cm, size 

 class 13) and smaller longhorn sculpin (<16 cm, 

 size class 3) (Fig. 2C). The peak value of 38% 

 occurred between two different predator size 

 classes, and in both instances the single most im- 

 portant prey contributing to this overlap was the 



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