HACUNDA: TROPHIC RELATIONSHIPS AMONG DEMERSAL FISHES 



Crangon septemspinosa was a principal prey 

 species. Mysids, cumaceans, and isopods were of 

 minor importance. Other groups (Algae, Porifera, 



Table 8. — Stomach contents of 30 red hake ranging from 15.0 to 

 40.1 cm (mean 25.6±6.1 cm) and 22 to 392 g(mean 121 ±86 g). 

 Three stomach.s were empty. IRI = index of relative importance 

 I see textK 



'Frequency of occurrence of food item. 



Polychaeta, Mollusca) constituted a small portion 

 of the diet. 



Dietary Overlap 



The fish community in Johns Bay showed a con- 

 siderable degree of food overlap (Table 9). Eight 

 species-pairs had overlap values -0.50. This is a 

 reflection of the dominance of crustaceans in the 

 diets of the predators examined. The greatest 

 dietary overlap occurred between the Atlantic cod 

 and longhorn sculpin. In addition, high dietary 

 overlaps occurred among the Atlantic cod, red 

 hake, longhorn sculpin, little skate, winter floun- 

 der, and yellowtail flounder, a consequence of the 

 dependence of these predators on amphipod and 

 decapod prey. 



Although over 100 prey taxa were found during 

 the study, only 13 were classified as principal prey. 

 In the partition plot predators that share principal 

 prey are generally arranged adjacent to one 

 another (Table 10). Difficulty in identifying di- 

 gested organisms necessitated using the broad 

 classification of Polychaeta in this partition plot. 

 Generally, predators consumed 4 or 5 principal 

 prey, and the percentage reoccurrence of principal 



Table 9. — A summary of the predator feeding habits and food overlap in fishes from Johns Bay, Maine. Species pairs with 



overlaps 0.50 or greater are in italics. 



Table lO. — Partition plot of principal prey for demersal fishes in Johns Bay, Maine. Numbers listed are index of 

 relative impwrtance values for prmcipal prey. Prey classifiction: (I) Infaunal, lEi Epifaunal, iN) Nektonic. 



Prey 



Ocean pout Windowpane 



Unciola (!) 

 Leptocheirus (I) 

 Crangon (E) 

 Polychaeta (!) 

 Cerastoderma (I) 

 Aeginella (E) 

 My sis (N) 

 Monoculodes (I) 

 Ampelisca (I) 

 Diastylis (I) 

 Cancer (E) 

 Echinarachnius (E) 

 Clupea (N) 



250 



310 



1,551 



1,166 



131 



'Indicates most important principal prey of prey of predator. 



'3.874 

 190 



463 

 200 



'9,933 



781 



