HACUNDA: TROPHIC RELATIONSHIPS AMONG DEMERSAL FISHES 



predators. The total number of reoccurrences pos- 

 sible is obtained by the number of predators minus 

 one, multiplied by the number of prey. The per- 

 centage reoccurrence of principal prey was calcu- 

 lated a second way by modifying the above pro- 

 cedure and ranking the principal prey in each 

 predator s diet in terms of relative importance 

 (e.g., first = 4 points, second = 3 points, third = 2 

 points, fourth = 1 point, each additional principal 

 prey = V2 point). In this case, points are totaled 

 for principal prey that are shared by two or more 

 predators, and this value is divided by the total 

 points possible if complete overlap occurred for 

 all principal prey in all predators, the result 

 being multiplied by 100 to give a percentage. 



I made length measurements of crustacean prey 

 species for several predators according to the pro- 

 cedure used by Ross (1977). A sample (Ns=25) of 

 each principal prey species was measured for sev- 

 eral specimens of each predator. Measurements 

 were made to the nearest millimeter along the 

 axis of greatest dimension. Mouth measurements 

 offish species were also taken to compare prey size 

 with mouth morphology. Upper jaw length was the 

 distance from the posterior end of the maxillary to 

 the tip of the snout. Mouth width was the distance 

 between the posterior edges of the maxillaries 

 with the mouth fully closed. 



I collected benthic samples in September using a 

 ponar grab. A series of three transects was estab- 

 lished along the trawl tract (Figure 1). Three sta- 

 tions at different depths were sampled along each 

 transect. Each ponar grab sampled a 0.05 m^ area. 

 Samples were washed through a 0.5 mm sieve and 

 then fixed in 10% Formalin. I analyzed grab sam- 

 ples in the same manner as the stomach con- 

 tents. 



RESULTS 



Abundance of Fishes 



Twenty species offish were collected during the 

 13-mo sampling period. The most abundant 

 species were the longhorn sculpin, Myoxocephalus 

 octodecemspinosus , and the winter flounder, 

 Pseudopleuronectes americanus. The fish com- 

 munity showed the greatest diversity and abun- 

 dance during summer. From January to March the 

 fish fauna was limited and no fish at all were taken 

 in the February sample. 



The fish community can be broken down into 



different temporal components (Tyler 1971). "Reg- 

 ulars" were those species present on nearly every 

 sampling date and included the longhorn sculpin; 

 winter flounder; yellowtail flounder, Limanda fer- 

 ruginea; and the Atlantic cod, Gadus morhua. 

 "Summer periodics" were those species found in 

 samples taken during the warmer months: the 

 windowpane, Scopthalmus aquosus; ocean pout, 

 Macrozoarces americanus; red hake, Urophycis 

 chuss; and little skate. Raja erinacea. There was 

 no corresponding "winter periodics" group. "Occa- 

 sionals" were fish that occurred in low numbers at 

 infrequent intervals: the sea raven, Hemitripterus 

 americanus; the winter skate, R. ocellata; thorny 

 skate, R. radiata; American plaice, Hippoglos- 

 soides platessoides; fourspotted flounder, 

 Paralichthys oblongus; witch flounder, Glyp- 

 tocephalus cynoglossus; cunner, Tautogolabrus 

 adspersus; silver hake, Merluccius bilinearis; 

 white hake, Urophycis tenuis; alligatorfish, As- 

 pidophoroides monopterygius; moustache sculpin, 

 Triglops murrayi; and sand lance, Ammodytes 

 sp. 



Foods 



I examined the foods of the eight most abundant 

 species (longhorn sculpin, winter flounder, win- 

 dowpane, yellowtail flounder, ocean pout, little 

 skate, Atlantic cod, and red hake). The diet for 

 each species for the entire sampling period is 

 summarized in Tables 1-8. 



Longhorn Sculpin 



Sixty-three prey taxa were identified in the 299 

 longhorn sculpin stomachs. Crustaceans were the 

 most important prey group, making up 58.4% of 

 the diet by weight and 95.8% of the diet by number 

 (Table 1). Amphipods were most heavily preyed 

 upon, especially Unciola sp. and Leptocheirus 

 pinguis, which had the two highest indices of 

 relative importance. Decapods were next in im- 

 portance, with the sand shrimp, Crangon sep- 

 temspinosa, and rock crab, Cancer irroratus, con- 

 stituting 18.2% of the diet by weight. Mysids, 

 principally Mysis mixta, were also significant 

 food items. Pisces were the second major prey 

 group and made up 25.2% of the diet by weight. 

 Larval Atlantic herring, Clupea harengus 

 harengus, were important fish prey Other phyla 

 (Porifera, Polychaeta, Mollusca) formed a minor 

 portion of the diet. 



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